path to node progress

Refactor: Move error types into their own submodule

.codespellrc

@@ -1,3 +1,3 @@
 [codespell]
 ignore-words-list: crate,everytime
-skip: **/target,node_modules,build
+skip: **/target,node_modules,build,**/Cargo.lock

.env.development

@@ -1,6 +1,6 @@
-VITE_KC_API_WS_MODELING_URL=wss://api.dev.kittycad.io/ws/modeling/commands
-VITE_KC_API_BASE_URL=https://api.dev.kittycad.io
-VITE_KC_SITE_BASE_URL=https://dev.kittycad.io
+VITE_KC_API_WS_MODELING_URL=wss://api.dev.zoo.dev/ws/modeling/commands
+VITE_KC_API_BASE_URL=https://api.dev.zoo.dev
+VITE_KC_SITE_BASE_URL=https://dev.zoo.dev
 VITE_KC_SKIP_AUTH=false
 VITE_KC_CONNECTION_TIMEOUT_MS=5000
 VITE_KC_SENTRY_DSN=

.env.production

@@ -1,5 +1,5 @@
-VITE_KC_API_WS_MODELING_URL=wss://api.kittycad.io/ws/modeling/commands
-VITE_KC_API_BASE_URL=https://api.kittycad.io
+VITE_KC_API_WS_MODELING_URL=wss://api.zoo.dev/ws/modeling/commands
+VITE_KC_API_BASE_URL=https://api.zoo.dev
 VITE_KC_SITE_BASE_URL=https://zoo.dev
 VITE_KC_SKIP_AUTH=false
 VITE_KC_CONNECTION_TIMEOUT_MS=15000

.github/workflows/cargo-clippy.yml

@@ -43,17 +43,6 @@ jobs:
       - name: Rust Cache
         uses: Swatinem/rust-cache@v2.6.1
 
-      - name: Install ffmpeg
-        run: |
-          sudo apt update
-          sudo apt install \
-            ffmpeg \
-            libavformat-dev \
-            libavutil-dev \
-            libclang-dev \
-            libswscale-dev \
-            --no-install-recommends
-
       - name: Run clippy
         run: |
           cd "${{ matrix.dir }}"

.github/workflows/cargo-test.yml

@@ -44,16 +44,6 @@ jobs:
       - uses: taiki-e/install-action@nextest
       - name: Rust Cache
         uses: Swatinem/rust-cache@v2.6.1
-      - name: Install ffmpeg
-        run: |
-          sudo apt update
-          sudo apt install \
-            ffmpeg \
-            libavformat-dev \
-            libavutil-dev \
-            libclang-dev \
-            libswscale-dev \
-            --no-install-recommends
       - name: cargo test
         shell: bash
         run: |-

.github/workflows/ci.yml

@@ -123,6 +123,7 @@ jobs:
     needs: [prepare-json-files]
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
         os: [macos-latest, ubuntu-latest, windows-latest]
     steps:
@@ -243,6 +244,7 @@ jobs:
           args: "${{ matrix.os == 'macos-latest' && '--target universal-apple-darwin' || '' }} ${{ env.TAURI_CONF_ARGS }}"
 
       - uses: actions/upload-artifact@v3
+        if: matrix.os != 'ubuntu-latest'
         env:
           PREFIX: ${{ matrix.os == 'macos-latest' && 'src-tauri/target/universal-apple-darwin' || 'src-tauri/target' }}
           MODE: ${{ env.BUILD_RELEASE == 'true' && 'release' || 'debug' }}
@@ -279,7 +281,6 @@ jobs:
         run: |
           ls -l artifact/*/*oo*
           DARWIN_SIG=`cat artifact/macos/*.app.tar.gz.sig`
-          LINUX_SIG=`cat artifact/appimage/*.AppImage.tar.gz.sig`
           WINDOWS_SIG=`cat artifact/msi/*.msi.zip.sig`
           RELEASE_DIR=https://${WEBSITE_DIR}/${VERSION}
           jq --null-input \
@@ -288,8 +289,6 @@ jobs:
             --arg notes "${NOTES}" \
             --arg darwin_sig "$DARWIN_SIG" \
             --arg darwin_url "$RELEASE_DIR/macos/Zoo%20Modeling%20App.app.tar.gz" \
-            --arg linux_sig "$LINUX_SIG" \
-            --arg linux_url "$RELEASE_DIR/appimage/zoo-modeling-app_${VERSION_NO_V}_amd64.AppImage.tar.gz" \
             --arg windows_sig "$WINDOWS_SIG" \
             --arg windows_url "$RELEASE_DIR/msi/Zoo%20Modeling%20App_${VERSION_NO_V}_x64_en-US.msi.zip" \
             '{
@@ -305,10 +304,6 @@ jobs:
                   "signature": $darwin_sig,
                   "url": $darwin_url
                 },
-                "linux-x86_64": {
-                  "signature": $linux_sig,
-                  "url": $linux_url
-                },
                 "windows-x86_64": {
                   "signature": $windows_sig,
                   "url": $windows_url
@@ -325,7 +320,6 @@ jobs:
             --arg pub_date "${PUB_DATE}" \
             --arg notes "${NOTES}" \
             --arg darwin_url "$RELEASE_DIR/dmg/Zoo%20Modeling%20App_${VERSION_NO_V}_universal.dmg" \
-            --arg linux_url "$RELEASE_DIR/appimage/zoo-modeling-app_${VERSION_NO_V}_amd64.AppImage" \
             --arg windows_url "$RELEASE_DIR/msi/Zoo%20Modeling%20App_${VERSION_NO_V}_x64_en-US.msi" \
             '{
               "version": $version,
@@ -335,9 +329,6 @@ jobs:
                 "dmg-universal": {
                   "url": $darwin_url
                 },
-                "appimage-x86_64": {
-                  "url": $linux_url
-                },
                 "msi-x86_64": {
                   "url": $windows_url
                 }
@@ -359,7 +350,7 @@ jobs:
         uses: google-github-actions/upload-cloud-storage@v2.0.0
         with:
           path: artifact
-          glob: '*/*oo*'
+          glob: '*/Zoo*'
           parent: false
           destination: ${{ env.BUCKET_DIR }}/${{ env.VERSION }}
 
@@ -379,4 +370,4 @@ jobs:
         if: ${{ github.event_name == 'release' }}
         uses: softprops/action-gh-release@v1
         with:
-          files: artifact/*/*oo*
+          files: 'artifact/*/Zoo*'

README.md

@@ -94,7 +94,6 @@ For running the rust (not tauri rust though) only, you can
 cd src/wasm-lib
 cargo test
 ```
-but you will need to have install ffmpeg prior to.
 
 ## Tauri
 

e2e/tauri/specs/auth.e2e.ts

@@ -1,19 +1,26 @@
 import { browser, $, expect } from '@wdio/globals'
 import fs from 'fs/promises'
 
-describe('KCMA (Tauri, Linux)', () => {
-  it('opens the auth page, signs in, and signs out', async () => {
-    // Clean up previous tests
+const defaultDir = `${process.env.HOME}/Documents/zoo-modeling-app-projects`
+const userCodeDir = '/tmp/kittycad_user_code'
+
+async function click(element: WebdriverIO.Element): Promise<void> {
+  // Workaround for .click(), see https://github.com/tauri-apps/tauri/issues/6541
+  await element.waitForClickable()
+  await browser.execute('arguments[0].click();', element)
+}
+
+describe('ZMA (Tauri, Linux)', () => {
+  it('opens the auth page and signs in', async () => {
+    // Clean up filesystem from previous tests
     await new Promise((resolve) => setTimeout(resolve, 100))
-    await fs.rm('/tmp/kittycad_user_code', { force: true })
-    await browser.execute('window.localStorage.clear()')
+    await fs.rm(defaultDir, { force: true, recursive: true })
+    await fs.rm(userCodeDir, { force: true })
 
     const signInButton = await $('[data-testid="sign-in-button"]')
     expect(await signInButton.getText()).toEqual('Sign in')
 
-    // Workaround for .click(), see https://github.com/tauri-apps/tauri/issues/6541
-    await signInButton.waitForClickable()
-    await browser.execute('arguments[0].click();', signInButton)
+    await click(signInButton)
     await new Promise((resolve) => setTimeout(resolve, 2000))
 
     // Get from main.rs
@@ -49,14 +56,51 @@ describe('KCMA (Tauri, Linux)', () => {
     // Now should be signed in
     const newFileButton = await $('[data-testid="home-new-file"]')
     expect(await newFileButton.getText()).toEqual('New file')
+  })
 
-    // So let's sign out!
+  it('opens the settings page, checks filesystem settings, and closes the settings page', async () => {
     const menuButton = await $('[data-testid="user-sidebar-toggle"]')
-    await menuButton.waitForClickable()
-    await browser.execute('arguments[0].click();', menuButton)
+    await click(menuButton)
+
+    const settingsButton = await $('[data-testid="settings-button"]')
+    await click(settingsButton)
+
+    const defaultDirInput = await $('[data-testid="default-directory-input"]')
+    expect(await defaultDirInput.getValue()).toEqual(defaultDir)
+
+    const nameInput = await $('[data-testid="name-input"]')
+    expect(await nameInput.getValue()).toEqual('project-$nnn')
+
+    const closeButton = await $('[data-testid="close-button"]')
+    await click(closeButton)
+  })
+
+  it('checks that no file exists, creates a new file', async () => {
+    const homeSection = await $('[data-testid="home-section"]')
+    expect(await homeSection.getText()).toContain('No Projects found')
+
+    const newFileButton = await $('[data-testid="home-new-file"]')
+    await click(newFileButton)
+    await new Promise((resolve) => setTimeout(resolve, 1000))
+
+    expect(await homeSection.getText()).toContain('project-000')
+  })
+
+  it('opens the new file and expects an error on Linux', async () => {
+    const projectLink = await $('[data-testid="project-link"]')
+    await click(projectLink)
+    const error = await $('h3')
+    expect(await error.getText()).toContain(
+      "Can't find variable: RTCPeerConnection"
+    )
+    await browser.execute('window.location.href = "tauri://localhost/home"')
+  })
+
+  it('signs out', async () => {
+    const menuButton = await $('[data-testid="user-sidebar-toggle"]')
+    await click(menuButton)
     const signoutButton = await $('[data-testid="user-sidebar-sign-out"]')
-    await signoutButton.waitForClickable()
-    await browser.execute('arguments[0].click();', signoutButton)
+    await click(signoutButton)
     const newSignInButton = await $('[data-testid="sign-in-button"]')
     expect(await newSignInButton.getText()).toEqual('Sign in')
   })

index.html

@@ -14,8 +14,8 @@
     <link rel="stylesheet" href="https://use.typekit.net/zzv8rvm.css" />
     <script
       defer
-      data-domain="app.kittycad.io"
-      src="https://plausible.corp.kittycad.io/js/script.js"
+      data-domain="app.zoo.dev"
+      src="https://plausible.corp.zoo.dev/js/script.js"
     ></script>
     <title>Zoo Modeling App</title>
   </head>

package.json

@@ -136,7 +136,7 @@
     "prettier": "^2.8.0",
     "setimmediate": "^1.0.5",
     "tailwindcss": "^3.3.6",
-    "vite": "^4.5.0",
+    "vite": "^4.5.2",
     "vite-plugin-eslint": "^1.8.1",
     "vite-tsconfig-paths": "^4.2.1",
     "wait-on": "^7.2.0",

src-tauri/Cargo.lock

@@ -1242,9 +1242,9 @@ dependencies = [
 
 [[package]]
 name = "h2"
-version = "0.3.20"
+version = "0.3.24"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "97ec8491ebaf99c8eaa73058b045fe58073cd6be7f596ac993ced0b0a0c01049"
+checksum = "bb2c4422095b67ee78da96fbb51a4cc413b3b25883c7717ff7ca1ab31022c9c9"
 dependencies = [
  "bytes",
  "fnv",
@@ -1252,7 +1252,7 @@ dependencies = [
  "futures-sink",
  "futures-util",
  "http",
- "indexmap 1.9.3",
+ "indexmap 2.0.0",
  "slab",
  "tokio",
  "tokio-util",

src/Router.tsx

@@ -112,6 +112,7 @@ export type ProjectWithEntryPointMetadata = FileEntry & {
 }
 export type HomeLoaderData = {
   projects: ProjectWithEntryPointMetadata[]
+  newDefaultDirectory?: string
 }
 
 type CreateBrowserRouterArg = Parameters<typeof createBrowserRouter>[0]
@@ -259,6 +260,7 @@ const router = createBrowserRouter(
         const projectDir = await initializeProjectDirectory(
           persistedSettings.defaultDirectory || ''
         )
+        let newDefaultDirectory: string | undefined = undefined
         if (projectDir !== persistedSettings.defaultDirectory) {
           localStorage.setItem(
             SETTINGS_PERSIST_KEY,
@@ -267,6 +269,7 @@ const router = createBrowserRouter(
               defaultDirectory: projectDir,
             })
           )
+          newDefaultDirectory = projectDir
         }
         const projectsNoMeta = (await readDir(projectDir)).filter(
           isProjectDirectory
@@ -282,6 +285,7 @@ const router = createBrowserRouter(
 
         return {
           projects,
+          newDefaultDirectory,
         }
       },
       children: [

src/components/ProjectCard.tsx

@@ -107,6 +107,7 @@ function ProjectCard({
             <Link
               className="flex-1 text-liquid-100 after:content-[''] after:absolute after:inset-0"
               to={`${paths.FILE}/${encodeURIComponent(project.path)}`}
+              data-testid="project-link"
             >
               {project.name?.replace(FILE_EXT, '')}
             </Link>

src/components/Stream.tsx

@@ -7,7 +7,7 @@ import {
 } from 'react'
 import { v4 as uuidv4 } from 'uuid'
 import { useStore } from '../useStore'
-import { getNormalisedCoordinates } from '../lib/utils'
+import { getNormalisedCoordinates, throttle } from '../lib/utils'
 import Loading from './Loading'
 import { cameraMouseDragGuards } from 'lib/cameraControls'
 import { useGlobalStateContext } from 'hooks/useGlobalStateContext'
@@ -115,9 +115,9 @@ export const Stream = ({ className = '' }) => {
     setClickCoords({ x, y })
   }
 
-  const handleScroll: WheelEventHandler<HTMLVideoElement> = (e) => {
+  const fps = 60
+  const handleScroll: WheelEventHandler<HTMLVideoElement> = throttle((e) => {
     if (!cameraMouseDragGuards[cameraControls].zoom.scrollCallback(e)) return
-
     engineCommandManager.sendSceneCommand({
       type: 'modeling_cmd_req',
       cmd: {
@@ -126,7 +126,7 @@ export const Stream = ({ className = '' }) => {
       },
       cmd_id: uuidv4(),
     })
-  }
+  }, Math.round(1000 / fps))
 
   const handleMouseUp: MouseEventHandler<HTMLVideoElement> = ({
     clientX,

src/components/UserSidebarMenu.tsx

@@ -128,6 +128,7 @@ const UserSidebarMenu = ({ user }: { user?: User }) => {
                       : paths.HOME + paths.SETTINGS
                     navigate(targetPath)
                   }}
+                  data-testid="settings-button"
                 >
                   Settings
                 </ActionButton>

src/lang/std/engineConnection.ts

@@ -48,6 +48,72 @@ type Timeout = ReturnType<typeof setTimeout>
 
 type ClientMetrics = Models['ClientMetrics_type']
 
+type Value<T, U> = U extends undefined
+  ? { type: T; value: U }
+  : U extends void
+  ? { type: T }
+  : { type: T; value: U }
+
+type State<T, U> = Value<T, U>
+
+enum EngineConnectionStateType {
+  Fresh = 'fresh',
+  Connecting = 'connecting',
+  ConnectionEstablished = 'connection-established',
+  Disconnected = 'disconnected',
+}
+
+enum DisconnectedType {
+  Error = 'error',
+  Timeout = 'timeout',
+  Quit = 'quit',
+}
+
+type DisconnectedValue =
+  | State<DisconnectedType.Error, Error | undefined>
+  | State<DisconnectedType.Timeout, void>
+  | State<DisconnectedType.Quit, void>
+
+// These are ordered by the expected sequence.
+enum ConnectingType {
+  WebSocketConnecting = 'websocket-connecting',
+  WebSocketEstablished = 'websocket-established',
+  PeerConnectionCreated = 'peer-connection-created',
+  ICEServersSet = 'ice-servers-set',
+  SetLocalDescription = 'set-local-description',
+  OfferedSdp = 'offered-sdp',
+  ReceivedSdp = 'received-sdp',
+  SetRemoteDescription = 'set-remote-description',
+  WebRTCConnecting = 'webrtc-connecting',
+  ICECandidateReceived = 'ice-candidate-received',
+  TrackReceived = 'track-received',
+  DataChannelRequested = 'data-channel-requested',
+  DataChannelConnecting = 'data-channel-connecting',
+  DataChannelEstablished = 'data-channel-established',
+}
+
+type ConnectingValue =
+  | State<ConnectingType.WebSocketConnecting, void>
+  | State<ConnectingType.WebSocketEstablished, void>
+  | State<ConnectingType.PeerConnectionCreated, void>
+  | State<ConnectingType.ICEServersSet, void>
+  | State<ConnectingType.SetLocalDescription, void>
+  | State<ConnectingType.OfferedSdp, void>
+  | State<ConnectingType.ReceivedSdp, void>
+  | State<ConnectingType.SetRemoteDescription, void>
+  | State<ConnectingType.WebRTCConnecting, void>
+  | State<ConnectingType.TrackReceived, void>
+  | State<ConnectingType.ICECandidateReceived, void>
+  | State<ConnectingType.DataChannelRequested, string>
+  | State<ConnectingType.DataChannelConnecting, string>
+  | State<ConnectingType.DataChannelEstablished, void>
+
+type EngineConnectionState =
+  | State<EngineConnectionStateType.Fresh, void>
+  | State<EngineConnectionStateType.Connecting, ConnectingValue>
+  | State<EngineConnectionStateType.ConnectionEstablished, void>
+  | State<EngineConnectionStateType.Disconnected, DisconnectedValue>
+
 // EngineConnection encapsulates the connection(s) to the Engine
 // for the EngineCommandManager; namely, the underlying WebSocket
 // and WebRTC connections.
@@ -55,10 +121,28 @@ class EngineConnection {
   websocket?: WebSocket
   pc?: RTCPeerConnection
   unreliableDataChannel?: RTCDataChannel
+  mediaStream?: MediaStream
+
+  private _state: EngineConnectionState = {
+    type: EngineConnectionStateType.Fresh,
+  }
+
+  get state(): EngineConnectionState {
+    return this._state
+  }
+
+  set state(next: EngineConnectionState) {
+    console.log(`${JSON.stringify(this.state)} → ${JSON.stringify(next)}`)
+    if (next.type === EngineConnectionStateType.Disconnected) {
+      console.trace()
+      const sub = next.value
+      if (sub.type === DisconnectedType.Error) {
+        console.error(sub.value)
+      }
+    }
+    this._state = next
+  }
 
-  private ready: boolean
-  private connecting: boolean
-  private dead: boolean
   private failedConnTimeout: Timeout | null
 
   readonly url: string
@@ -94,74 +178,77 @@ class EngineConnection {
   }) {
     this.url = url
     this.token = token
-    this.ready = false
-    this.connecting = false
-    this.dead = false
     this.failedConnTimeout = null
     this.onWebsocketOpen = onWebsocketOpen
     this.onDataChannelOpen = onDataChannelOpen
     this.onEngineConnectionOpen = onEngineConnectionOpen
     this.onConnectionStarted = onConnectionStarted
+
     this.onClose = onClose
     this.onNewTrack = onNewTrack
 
     // TODO(paultag): This ought to be tweakable.
     const pingIntervalMs = 10000
 
+    // Without an interval ping, our connection will timeout.
     let pingInterval = setInterval(() => {
-      if (this.dead) {
-        clearInterval(pingInterval)
-      }
-      if (this.isReady()) {
-        // When we're online, every 10 seconds, we'll attempt to put a 'ping'
-        // command through the WebSocket connection. This will help both ends
-        // of the connection maintain the TCP connection without hitting a
-        // timeout condition.
-        this.send({ type: 'ping' })
+      switch (this.state.type as EngineConnectionStateType) {
+        case EngineConnectionStateType.ConnectionEstablished:
+          this.send({ type: 'ping' })
+          break
+        case EngineConnectionStateType.Disconnected:
+          clearInterval(pingInterval)
+          break
+        default:
+          break
       }
     }, pingIntervalMs)
 
     const connectionTimeoutMs = VITE_KC_CONNECTION_TIMEOUT_MS
-    let connectInterval = setInterval(() => {
-      if (this.dead) {
-        clearInterval(connectInterval)
-        return
+    let connectRetryInterval = setInterval(() => {
+      if (this.state.type !== EngineConnectionStateType.Disconnected) return
+      switch (this.state.value.type) {
+        case DisconnectedType.Error:
+          clearInterval(connectRetryInterval)
+          break
+        case DisconnectedType.Timeout:
+          console.log('Trying to reconnect')
+          this.connect()
+          break
+        default:
+          break
       }
-      if (this.isReady()) {
-        return
-      }
-      console.log('connecting via retry')
-      this.connect()
     }, connectionTimeoutMs)
   }
-  // isConnecting will return true when connect has been called, but the full
-  // WebRTC is not online.
+
   isConnecting() {
-    return this.connecting
+    return this.state.type === EngineConnectionStateType.Connecting
   }
-  // isReady will return true only when the WebRTC *and* WebSocket connection
-  // are connected. During setup, the WebSocket connection comes online first,
-  // which is used to establish the WebRTC connection. The EngineConnection
-  // is not "Ready" until both are connected.
+
   isReady() {
-    return this.ready
+    return this.state.type === EngineConnectionStateType.ConnectionEstablished
   }
+
   tearDown() {
-    this.dead = true
-    this.close()
+    this.disconnectAll()
+    this.state = {
+      type: EngineConnectionStateType.Disconnected,
+      value: { type: DisconnectedType.Quit },
+    }
   }
+
   // shouldTrace will return true when Sentry should be used to instrument
   // the Engine.
   shouldTrace() {
     return Sentry.getCurrentHub()?.getClient()?.getOptions()?.sendClientReports
   }
+
   // connect will attempt to connect to the Engine over a WebSocket, and
   // establish the WebRTC connections.
   //
   // This will attempt the full handshake, and retry if the connection
   // did not establish.
   connect() {
-    console.log('connect was called')
     if (this.isConnecting() || this.isReady()) {
       return
     }
@@ -195,71 +282,269 @@ class EngineConnection {
     let handshakeSpan: SpanPromise
     let iceSpan: SpanPromise
 
+    const spanStart = (op: string) =>
+      new SpanPromise(webrtcMediaTransaction.startChild({ op }))
+
     if (this.shouldTrace()) {
-      webrtcMediaTransaction = Sentry.startTransaction({
-        name: 'webrtc-media',
+      webrtcMediaTransaction = Sentry.startTransaction({ name: 'webrtc-media' })
+      websocketSpan = spanStart('websocket')
+    }
+
+    const createPeerConnection = () => {
+      this.pc = new RTCPeerConnection()
+
+      // Data channels MUST BE specified before SDP offers because requesting
+      // them affects what our needs are!
+      const DATACHANNEL_NAME_UMC = 'unreliable_modeling_cmds'
+      this.pc.createDataChannel(DATACHANNEL_NAME_UMC)
+
+      this.state = {
+        type: EngineConnectionStateType.Connecting,
+        value: {
+          type: ConnectingType.DataChannelRequested,
+          value: DATACHANNEL_NAME_UMC,
+        },
+      }
+
+      this.pc.addEventListener('icecandidate', (event) => {
+        if (event.candidate === null) {
+          return
+        }
+
+        this.state = {
+          type: EngineConnectionStateType.Connecting,
+          value: {
+            type: ConnectingType.ICECandidateReceived,
+          },
+        }
+
+        // Request a candidate to use
+        this.send({
+          type: 'trickle_ice',
+          candidate: event.candidate.toJSON(),
+        })
       })
-      websocketSpan = new SpanPromise(
-        webrtcMediaTransaction.startChild({ op: 'websocket' })
-      )
+
+      this.pc.addEventListener('icecandidateerror', (_event: Event) => {
+        const event = _event as RTCPeerConnectionIceErrorEvent
+        console.warn(
+          `ICE candidate returned an error: ${event.errorCode}: ${event.errorText} for ${event.url}`
+        )
+      })
+
+      // https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/connectionstatechange_event
+      // Event type: generic Event type...
+      this.pc.addEventListener('connectionstatechange', (event: any) => {
+        console.log('connectionstatechange: ' + event.target?.connectionState)
+        switch (event.target?.connectionState) {
+          // From what I understand, only after have we done the ICE song and
+          // dance is it safest to connect the video tracks / stream
+          case 'connected':
+            if (this.shouldTrace()) {
+              iceSpan.resolve?.()
+            }
+
+            // Let the browser attach to the video stream now
+            this.onNewTrack({ conn: this, mediaStream: this.mediaStream! })
+            break
+          case 'failed':
+            this.disconnectAll()
+            this.state = {
+              type: EngineConnectionStateType.Disconnected,
+              value: {
+                type: DisconnectedType.Error,
+                value: new Error(
+                  'failed to negotiate ice connection; restarting'
+                ),
+              },
+            }
+            break
+          default:
+            break
+        }
+      })
+
+      this.pc.addEventListener('track', (event) => {
+        const mediaStream = event.streams[0]
+
+        this.state = {
+          type: EngineConnectionStateType.Connecting,
+          value: {
+            type: ConnectingType.TrackReceived,
+          },
+        }
+
+        if (this.shouldTrace()) {
+          let mediaStreamTrack = mediaStream.getVideoTracks()[0]
+          mediaStreamTrack.addEventListener('unmute', () => {
+            // let settings = mediaStreamTrack.getSettings()
+            // mediaTrackSpan.span.setTag("fps", settings.frameRate)
+            // mediaTrackSpan.span.setTag("width", settings.width)
+            // mediaTrackSpan.span.setTag("height", settings.height)
+            mediaTrackSpan.resolve?.()
+          })
+        }
+
+        this.webrtcStatsCollector = (): Promise<ClientMetrics> => {
+          return new Promise((resolve, reject) => {
+            if (mediaStream.getVideoTracks().length !== 1) {
+              reject(new Error('too many video tracks to report'))
+              return
+            }
+
+            let videoTrack = mediaStream.getVideoTracks()[0]
+            void this.pc?.getStats(videoTrack).then((videoTrackStats) => {
+              let client_metrics: ClientMetrics = {
+                rtc_frames_decoded: 0,
+                rtc_frames_dropped: 0,
+                rtc_frames_received: 0,
+                rtc_frames_per_second: 0,
+                rtc_freeze_count: 0,
+                rtc_jitter_sec: 0.0,
+                rtc_keyframes_decoded: 0,
+                rtc_total_freezes_duration_sec: 0.0,
+              }
+
+              // TODO(paultag): Since we can technically have multiple WebRTC
+              // video tracks (even if the Server doesn't at the moment), we
+              // ought to send stats for every video track(?), and add the stream
+              // ID into it.  This raises the cardinality of collected metrics
+              // when/if we do, but for now, just report the one stream.
+
+              videoTrackStats.forEach((videoTrackReport) => {
+                if (videoTrackReport.type === 'inbound-rtp') {
+                  client_metrics.rtc_frames_decoded =
+                    videoTrackReport.framesDecoded || 0
+                  client_metrics.rtc_frames_dropped =
+                    videoTrackReport.framesDropped || 0
+                  client_metrics.rtc_frames_received =
+                    videoTrackReport.framesReceived || 0
+                  client_metrics.rtc_frames_per_second =
+                    videoTrackReport.framesPerSecond || 0
+                  client_metrics.rtc_freeze_count =
+                    videoTrackReport.freezeCount || 0
+                  client_metrics.rtc_jitter_sec = videoTrackReport.jitter || 0.0
+                  client_metrics.rtc_keyframes_decoded =
+                    videoTrackReport.keyFramesDecoded || 0
+                  client_metrics.rtc_total_freezes_duration_sec =
+                    videoTrackReport.totalFreezesDuration || 0
+                } else if (videoTrackReport.type === 'transport') {
+                  // videoTrackReport.bytesReceived,
+                  // videoTrackReport.bytesSent,
+                }
+              })
+              resolve(client_metrics)
+            })
+          })
+        }
+
+        // The app is eager to use the MediaStream; as soon as onNewTrack is
+        // called, the following sequence happens:
+        // EngineConnection.onNewTrack -> StoreState.setMediaStream ->
+        // Stream.tsx reacts to mediaStream change, setting a video element.
+        // We wait until connectionstatechange changes to "connected"
+        // to pass it to the rest of the application.
+
+        this.mediaStream = mediaStream
+      })
+
+      this.pc.addEventListener('datachannel', (event) => {
+        this.unreliableDataChannel = event.channel
+
+        this.state = {
+          type: EngineConnectionStateType.Connecting,
+          value: {
+            type: ConnectingType.DataChannelConnecting,
+            value: event.channel.label,
+          },
+        }
+
+        this.unreliableDataChannel.addEventListener('open', (event) => {
+          this.state = {
+            type: EngineConnectionStateType.Connecting,
+            value: {
+              type: ConnectingType.DataChannelEstablished,
+            },
+          }
+
+          if (this.shouldTrace()) {
+            dataChannelSpan.resolve?.()
+          }
+
+          this.onDataChannelOpen(this)
+
+          // Everything is now connected.
+          this.state = { type: EngineConnectionStateType.ConnectionEstablished }
+
+          this.onEngineConnectionOpen(this)
+        })
+
+        this.unreliableDataChannel.addEventListener('close', (event) => {
+          console.log(event)
+          console.log('unreliable data channel closed')
+          this.disconnectAll()
+          this.unreliableDataChannel = undefined
+
+          if (this.areAllConnectionsClosed()) {
+            this.state = {
+              type: EngineConnectionStateType.Disconnected,
+              value: { type: DisconnectedType.Quit },
+            }
+          }
+        })
+
+        this.unreliableDataChannel.addEventListener('error', (event) => {
+          this.disconnectAll()
+
+          this.state = {
+            type: EngineConnectionStateType.Disconnected,
+            value: {
+              type: DisconnectedType.Error,
+              value: new Error(event.toString()),
+            },
+          }
+        })
+      })
+    }
+
+    this.state = {
+      type: EngineConnectionStateType.Connecting,
+      value: {
+        type: ConnectingType.WebSocketConnecting,
+      },
     }
 
     this.websocket = new WebSocket(this.url, [])
     this.websocket.binaryType = 'arraybuffer'
 
-    this.pc = new RTCPeerConnection()
-    this.pc.createDataChannel('unreliable_modeling_cmds')
     this.websocket.addEventListener('open', (event) => {
-      console.log('Connected to websocket, waiting for ICE servers')
+      this.state = {
+        type: EngineConnectionStateType.Connecting,
+        value: {
+          type: ConnectingType.WebSocketEstablished,
+        },
+      }
+
+      this.onWebsocketOpen(this)
+
+      // This is required for when KCMA is running stand-alone / within Tauri.
+      // Otherwise when run in a browser, the token is sent implicitly via
+      // the Cookie header.
       if (this.token) {
         this.send({ headers: { Authorization: `Bearer ${this.token}` } })
       }
-    })
 
-    this.pc.addEventListener('icecandidateerror', (_event) => {
-      const event = _event as RTCPeerConnectionIceErrorEvent
-      console.error(
-        `ICE candidate returned an error: ${event.errorCode}: ${event.errorText} for ${event.url}`
-      )
-    })
-
-    this.pc.addEventListener('connectionstatechange', (event) => {
-      if (this.pc?.iceConnectionState === 'connected') {
-        if (this.shouldTrace()) {
-          iceSpan.resolve?.()
-        }
-      } else if (this.pc?.iceConnectionState === 'failed') {
-        // failed is a terminal state; let's explicitly kill the
-        // connection to the server at this point.
-        console.log('failed to negotiate ice connection; restarting')
-        this.close()
-      }
-    })
-
-    this.websocket.addEventListener('open', (event) => {
       if (this.shouldTrace()) {
         websocketSpan.resolve?.()
 
-        handshakeSpan = new SpanPromise(
-          webrtcMediaTransaction.startChild({ op: 'handshake' })
-        )
-        iceSpan = new SpanPromise(
-          webrtcMediaTransaction.startChild({ op: 'ice' })
-        )
-        dataChannelSpan = new SpanPromise(
-          webrtcMediaTransaction.startChild({
-            op: 'data-channel',
-          })
-        )
-        mediaTrackSpan = new SpanPromise(
-          webrtcMediaTransaction.startChild({
-            op: 'media-track',
-          })
-        )
+        handshakeSpan = spanStart('handshake')
+        iceSpan = spanStart('ice')
+        dataChannelSpan = spanStart('data-channel')
+        mediaTrackSpan = spanStart('media-track')
       }
 
       if (this.shouldTrace()) {
-        Promise.all([
+        void Promise.all([
           handshakeSpan.promise,
           iceSpan.promise,
           dataChannelSpan.promise,
@@ -269,18 +554,30 @@ class EngineConnection {
           webrtcMediaTransaction?.finish()
         })
       }
-
-      this.onWebsocketOpen(this)
     })
 
     this.websocket.addEventListener('close', (event) => {
-      console.log('websocket connection closed', event)
-      this.close()
+      this.disconnectAll()
+      this.websocket = undefined
+
+      if (this.areAllConnectionsClosed()) {
+        this.state = {
+          type: EngineConnectionStateType.Disconnected,
+          value: { type: DisconnectedType.Quit },
+        }
+      }
     })
 
     this.websocket.addEventListener('error', (event) => {
-      console.log('websocket connection error', event)
-      this.close()
+      this.disconnectAll()
+
+      this.state = {
+        type: EngineConnectionStateType.Disconnected,
+        value: {
+          type: DisconnectedType.Error,
+          value: new Error(event.toString()),
+        },
+      }
     })
 
     this.websocket.addEventListener('message', (event) => {
@@ -314,28 +611,137 @@ class EngineConnection {
       }
 
       let resp = message.resp
-      if (!resp) {
-        // If there's no body to the response, we can bail here.
+
+      // If there's no body to the response, we can bail here.
+      // !resp.type is usually "pong" response for our "ping"
+      if (!resp || !resp.type) {
         return
       }
 
-      if (resp.type === 'sdp_answer') {
-        let answer = resp.data?.answer
-        if (!answer || answer.type === 'unspecified') {
-          return
-        }
+      console.log('received', resp)
 
-        if (this.pc?.signalingState !== 'stable') {
-          // If the connection is stable, we shouldn't bother updating the
-          // SDP, since we have a stable connection to the backend. If we
-          // need to renegotiate, the whole PeerConnection needs to get
-          // tore down.
-          this.pc?.setRemoteDescription(
-            new RTCSessionDescription({
-              type: answer.type,
-              sdp: answer.sdp,
+      switch (resp.type) {
+        case 'ice_server_info':
+          let ice_servers = resp.data?.ice_servers
+
+          // Now that we have some ICE servers it makes sense
+          // to start initializing the RTCPeerConnection. RTCPeerConnection
+          // will begin the ICE process.
+          createPeerConnection()
+
+          this.state = {
+            type: EngineConnectionStateType.Connecting,
+            value: {
+              type: ConnectingType.PeerConnectionCreated,
+            },
+          }
+
+          // No ICE servers can be valid in a local dev. env.
+          if (ice_servers?.length === 0) {
+            console.warn('No ICE servers')
+            this.pc?.setConfiguration({})
+          } else {
+            // When we set the Configuration, we want to always force
+            // iceTransportPolicy to 'relay', since we know the topology
+            // of the ICE/STUN/TUN server and the engine. We don't wish to
+            // talk to the engine in any configuration /other/ than relay
+            // from a infra POV.
+            this.pc?.setConfiguration({
+              iceServers: ice_servers,
+              iceTransportPolicy: 'relay',
             })
-          )
+          }
+
+          this.state = {
+            type: EngineConnectionStateType.Connecting,
+            value: {
+              type: ConnectingType.ICEServersSet,
+            },
+          }
+
+          // We have an ICE Servers set now. We just setConfiguration, so let's
+          // start adding things we care about to the PeerConnection and let
+          // ICE negotiation happen in the background. Everything from here
+          // until the end of this function is setup of our end of the
+          // PeerConnection and waiting for events to fire our callbacks.
+
+          // Add a transceiver to our SDP offer
+          this.pc?.addTransceiver('video', {
+            direction: 'recvonly',
+          })
+
+          // Create a session description offer based on our local environment
+          // that we will send to the remote end. The remote will send back
+          // what it supports via sdp_answer.
+          this.pc
+            ?.createOffer()
+            .then((offer: RTCSessionDescriptionInit) => {
+              console.log(offer)
+              this.state = {
+                type: EngineConnectionStateType.Connecting,
+                value: {
+                  type: ConnectingType.SetLocalDescription,
+                },
+              }
+              return this.pc?.setLocalDescription(offer).then(() => {
+                this.send({
+                  type: 'sdp_offer',
+                  offer,
+                })
+                this.state = {
+                  type: EngineConnectionStateType.Connecting,
+                  value: {
+                    type: ConnectingType.OfferedSdp,
+                  },
+                }
+              })
+            })
+            .catch((error: Error) => {
+              console.error(error)
+              // The local description is invalid, so there's no point continuing.
+              this.disconnectAll()
+              this.state = {
+                type: EngineConnectionStateType.Disconnected,
+                value: {
+                  type: DisconnectedType.Error,
+                  value: error,
+                },
+              }
+            })
+          break
+
+        case 'sdp_answer':
+          let answer = resp.data?.answer
+          if (!answer || answer.type === 'unspecified') {
+            return
+          }
+
+          this.state = {
+            type: EngineConnectionStateType.Connecting,
+            value: {
+              type: ConnectingType.ReceivedSdp,
+            },
+          }
+
+          // As soon as this is set, RTCPeerConnection tries to
+          // establish a connection.
+          // @ts-ignore
+          // Have to ignore because dom.ts doesn't have the right type
+          void this.pc?.setRemoteDescription(answer)
+
+          this.state = {
+            type: EngineConnectionStateType.Connecting,
+            value: {
+              type: ConnectingType.SetRemoteDescription,
+            },
+          }
+
+          this.state = {
+            type: EngineConnectionStateType.Connecting,
+            value: {
+              type: ConnectingType.WebRTCConnecting,
+            },
+          }
 
           if (this.shouldTrace()) {
             // When both ends have a local and remote SDP, we've been able to
@@ -343,194 +749,46 @@ class EngineConnection {
             // servers, but this is hand-shook.
             handshakeSpan.resolve?.()
           }
-        }
-      } else if (resp.type === 'trickle_ice') {
-        let candidate = resp.data?.candidate
-        this.pc?.addIceCandidate(candidate as RTCIceCandidateInit)
-      } else if (resp.type === 'ice_server_info' && this.pc) {
-        console.log('received ice_server_info')
-        let ice_servers = resp.data?.ice_servers
+          break
 
-        if (ice_servers?.length > 0) {
-          // When we set the Configuration, we want to always force
-          // iceTransportPolicy to 'relay', since we know the topology
-          // of the ICE/STUN/TUN server and the engine. We don't wish to
-          // talk to the engine in any configuration /other/ than relay
-          // from a infra POV.
-          this.pc.setConfiguration({
-            iceServers: ice_servers,
-            iceTransportPolicy: 'relay',
-          })
-        } else {
-          this.pc?.setConfiguration({})
-        }
+        case 'trickle_ice':
+          let candidate = resp.data?.candidate
+          console.log('trickle_ice: using this candidate: ', candidate)
+          void this.pc?.addIceCandidate(candidate as RTCIceCandidateInit)
+          break
 
-        // We have an ICE Servers set now. We just setConfiguration, so let's
-        // start adding things we care about to the PeerConnection and let
-        // ICE negotiation happen in the background. Everything from here
-        // until the end of this function is setup of our end of the
-        // PeerConnection and waiting for events to fire our callbacks.
-
-        this.pc.addEventListener('icecandidate', (event) => {
-          if (!this.pc || !this.websocket) return
-          if (event.candidate !== null) {
-            console.log('sending trickle ice candidate')
-            const { candidate } = event
-            this.send({
-              type: 'trickle_ice',
-              candidate: candidate.toJSON(),
-            })
-          }
-        })
-
-        // Offer to receive 1 video track
-        this.pc.addTransceiver('video', {})
-
-        // Finally (but actually firstly!), to kick things off, we're going to
-        // generate our SDP, set it on our PeerConnection, and let the server
-        // know about our capabilities.
-        this.pc
-          .createOffer()
-          .then(async (descriptionInit) => {
-            await this?.pc?.setLocalDescription(descriptionInit)
-            console.log('sent sdp_offer begin')
-            this.send({
-              type: 'sdp_offer',
-              offer: this.pc?.localDescription,
-            })
-          })
-          .catch(console.log)
-      } else if (resp.type === 'metrics_request') {
-        if (this.webrtcStatsCollector === undefined) {
-          // TODO: Error message here?
-          return
-        }
-        this.webrtcStatsCollector().then((client_metrics) => {
-          this.send({
-            type: 'metrics_response',
-            metrics: client_metrics,
-          })
-        })
-      }
-    })
-
-    this.pc.addEventListener('track', (event) => {
-      const mediaStream = event.streams[0]
-
-      if (this.shouldTrace()) {
-        let mediaStreamTrack = mediaStream.getVideoTracks()[0]
-        mediaStreamTrack.addEventListener('unmute', () => {
-          // let settings = mediaStreamTrack.getSettings()
-          // mediaTrackSpan.span.setTag("fps", settings.frameRate)
-          // mediaTrackSpan.span.setTag("width", settings.width)
-          // mediaTrackSpan.span.setTag("height", settings.height)
-          mediaTrackSpan.resolve?.()
-        })
-      }
-
-      this.webrtcStatsCollector = (): Promise<ClientMetrics> => {
-        return new Promise((resolve, reject) => {
-          if (mediaStream.getVideoTracks().length !== 1) {
-            reject(new Error('too many video tracks to report'))
+        case 'metrics_request':
+          if (this.webrtcStatsCollector === undefined) {
+            // TODO: Error message here?
             return
           }
-
-          let videoTrack = mediaStream.getVideoTracks()[0]
-          this.pc?.getStats(videoTrack).then((videoTrackStats) => {
-            let client_metrics: ClientMetrics = {
-              rtc_frames_decoded: 0,
-              rtc_frames_dropped: 0,
-              rtc_frames_received: 0,
-              rtc_frames_per_second: 0,
-              rtc_freeze_count: 0,
-              rtc_jitter_sec: 0.0,
-              rtc_keyframes_decoded: 0,
-              rtc_total_freezes_duration_sec: 0.0,
-            }
-
-            // TODO(paultag): Since we can technically have multiple WebRTC
-            // video tracks (even if the Server doesn't at the moment), we
-            // ought to send stats for every video track(?), and add the stream
-            // ID into it.  This raises the cardinality of collected metrics
-            // when/if we do, but for now, just report the one stream.
-
-            videoTrackStats.forEach((videoTrackReport) => {
-              if (videoTrackReport.type === 'inbound-rtp') {
-                client_metrics.rtc_frames_decoded =
-                  videoTrackReport.framesDecoded || 0
-                client_metrics.rtc_frames_dropped =
-                  videoTrackReport.framesDropped || 0
-                client_metrics.rtc_frames_received =
-                  videoTrackReport.framesReceived || 0
-                client_metrics.rtc_frames_per_second =
-                  videoTrackReport.framesPerSecond || 0
-                client_metrics.rtc_freeze_count =
-                  videoTrackReport.freezeCount || 0
-                client_metrics.rtc_jitter_sec = videoTrackReport.jitter || 0.0
-                client_metrics.rtc_keyframes_decoded =
-                  videoTrackReport.keyFramesDecoded || 0
-                client_metrics.rtc_total_freezes_duration_sec =
-                  videoTrackReport.totalFreezesDuration || 0
-              } else if (videoTrackReport.type === 'transport') {
-                // videoTrackReport.bytesReceived,
-                // videoTrackReport.bytesSent,
-              }
+          void this.webrtcStatsCollector().then((client_metrics) => {
+            this.send({
+              type: 'metrics_response',
+              metrics: client_metrics,
             })
-            resolve(client_metrics)
           })
-        })
+          break
       }
-
-      this.onNewTrack({
-        conn: this,
-        mediaStream: mediaStream,
-      })
-    })
-
-    this.pc.addEventListener('datachannel', (event) => {
-      this.unreliableDataChannel = event.channel
-
-      console.log('accepted unreliable data channel', event.channel.label)
-      this.unreliableDataChannel.addEventListener('open', (event) => {
-        console.log('unreliable data channel opened', event)
-        if (this.shouldTrace()) {
-          dataChannelSpan.resolve?.()
-        }
-
-        this.onDataChannelOpen(this)
-
-        this.ready = true
-        this.connecting = false
-        // Do this after we set the connection is ready to avoid errors when
-        // we try to send messages before the connection is ready.
-        this.onEngineConnectionOpen(this)
-      })
-
-      this.unreliableDataChannel.addEventListener('close', (event) => {
-        console.log('unreliable data channel closed')
-        this.close()
-      })
-
-      this.unreliableDataChannel.addEventListener('error', (event) => {
-        console.log('unreliable data channel error')
-        this.close()
-      })
     })
 
     const connectionTimeoutMs = VITE_KC_CONNECTION_TIMEOUT_MS
-
     if (this.failedConnTimeout) {
-      console.log('clearing timeout before set')
       clearTimeout(this.failedConnTimeout)
       this.failedConnTimeout = null
     }
-    console.log('timeout set')
     this.failedConnTimeout = setTimeout(() => {
       if (this.isReady()) {
         return
       }
-      console.log('engine connection timeout on connection, closing')
-      this.close()
+      this.failedConnTimeout = null
+      this.disconnectAll()
+      this.state = {
+        type: EngineConnectionStateType.Disconnected,
+        value: {
+          type: DisconnectedType.Timeout,
+        },
+      }
     }, connectionTimeoutMs)
 
     this.onConnectionStarted(this)
@@ -549,23 +807,15 @@ class EngineConnection {
       typeof message === 'string' ? message : JSON.stringify(message)
     )
   }
-  close() {
+  disconnectAll() {
     this.websocket?.close()
-    this.pc?.close()
     this.unreliableDataChannel?.close()
-    this.websocket = undefined
-    this.pc = undefined
-    this.unreliableDataChannel = undefined
+    this.pc?.close()
     this.webrtcStatsCollector = undefined
-    if (this.failedConnTimeout) {
-      console.log('closed timeout in close')
-      clearTimeout(this.failedConnTimeout)
-      this.failedConnTimeout = null
-    }
-
-    this.onClose(this)
-    this.ready = false
-    this.connecting = false
+  }
+  areAllConnectionsClosed() {
+    console.log(this.websocket, this.pc, this.unreliableDataChannel)
+    return !this.websocket && !this.pc && !this.unreliableDataChannel
   }
 }
 
@@ -685,7 +935,7 @@ export class EngineCommandManager {
         // We also do this here because we want to ensure we create the gizmo
         // and execute the code everytime the stream is restarted.
         const gizmoId = uuidv4()
-        this.sendSceneCommand({
+        void this.sendSceneCommand({
           type: 'modeling_cmd_req',
           cmd_id: gizmoId,
           cmd: {
@@ -698,7 +948,7 @@ export class EngineCommandManager {
         })
 
         // Initialize the planes.
-        this.initPlanes().then(() => {
+        void this.initPlanes().then(() => {
           // We execute the code here to make sure if the stream was to
           // restart in a session, we want to make sure to execute the code.
           // We force it to re-execute the code because we want to make sure
@@ -745,7 +995,7 @@ export class EngineCommandManager {
             // because in all other cases we send JSON strings. But in the case of
             // export we send a binary blob.
             // Pass this to our export function.
-            exportSave(event.data)
+            void exportSave(event.data)
           } else {
             const message: Models['WebSocketResponse_type'] = JSON.parse(
               event.data

src/lang/std/sketch.ts

@@ -45,7 +45,7 @@ export function getCoordsFromPaths(skGroup: SketchGroup, index = 0): Coords2d {
   } else if (!currentPath) {
     return [0, 0]
   }
-  if (currentPath.type === 'toPoint') {
+  if (currentPath.type === 'topoint') {
     return [currentPath.to[0], currentPath.to[1]]
   }
   return [0, 0]

src/lib/tauriFS.ts

@@ -38,7 +38,7 @@ export async function initializeProjectDirectory(directory: string) {
     docDirectory = await documentDir()
   } catch (e) {
     console.log('error', e)
-    docDirectory = await homeDir() // seems to work better on Linux
+    docDirectory = `${await homeDir()}Documents/` // for headless Linux (eg. Github Actions)
   }
 
   const INITIAL_DEFAULT_DIR = docDirectory + PROJECT_FOLDER

src/routes/Home.tsx

@@ -37,13 +37,20 @@ import { homeCommandBarConfig } from 'lib/commandBarConfigs/homeCommandConfig'
 const Home = () => {
   const { commandBarSend } = useCommandsContext()
   const navigate = useNavigate()
-  const { projects: loadedProjects } = useLoaderData() as HomeLoaderData
+  const { projects: loadedProjects, newDefaultDirectory } =
+    useLoaderData() as HomeLoaderData
   const {
     settings: {
       context: { defaultDirectory, defaultProjectName },
       send: sendToSettings,
     },
   } = useGlobalStateContext()
+  if (newDefaultDirectory) {
+    sendToSettings({
+      type: 'Set Default Directory',
+      data: { defaultDirectory: newDefaultDirectory },
+    })
+  }
 
   const [state, send] = useMachine(homeMachine, {
     context: {
@@ -222,7 +229,7 @@ const Home = () => {
             </ActionButton>
           </div>
         </section>
-        <section>
+        <section data-testid="home-section">
           <p className="my-4 text-sm text-chalkboard-80 dark:text-chalkboard-30">
             Loaded from{' '}
             <span className="text-energy-70 dark:text-energy-40">

src/routes/Onboarding/CodeEditor.tsx

@@ -29,7 +29,7 @@ export default function CodeEditor() {
             The left pane is where you write your code. It's a code editor with
             syntax highlighting and autocompletion. We've decided to take the
             difficult route of writing our own language—called <code>kcl</code>
-            —for describing geometry, because don't want to inherit all the
+            —for describing geometry, because we don't want to inherit all the
             other functionality from existing languages. We have a lot of ideas
             about how <code>kcl</code> will evolve, and we want to hear your
             thoughts on it.

src/routes/Settings.tsx

@@ -113,6 +113,7 @@ export const Settings = () => {
               'text-destroy-20 group-hover:text-destroy-10 hover:text-destroy-10',
           }}
           className="hover:border-destroy-40"
+          data-testid="close-button"
         >
           Close
         </ActionButton>
@@ -178,6 +179,7 @@ export const Settings = () => {
                   className="flex-1 px-2 bg-transparent"
                   value={defaultDirectory}
                   disabled
+                  data-testid="default-directory-input"
                 />
                 <ActionButton
                   Element="button"
@@ -209,6 +211,7 @@ export const Settings = () => {
                 }}
                 autoCapitalize="off"
                 autoComplete="off"
+                data-testid="name-input"
               />
             </SettingsSection>
           </>

src/wasm-lib/Cargo.toml

@@ -25,8 +25,8 @@ image = "0.24.7"
 kittycad = { workspace = true, default-features = true }
 pretty_assertions = "1.4.0"
 reqwest = { version = "0.11.22", default-features = false }
-tokio = { version = "1.34.0", features = ["rt-multi-thread", "macros", "time"] }
-twenty-twenty = "0.6.1"
+tokio = { version = "1.35.1", features = ["rt-multi-thread", "macros", "time"] }
+twenty-twenty = "0.7"
 uuid = { version = "1.6.1", features = ["v4", "js", "serde"] }
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
@@ -52,12 +52,17 @@ debug = true
 [workspace]
 members = [
 	"derive-docs",
+  "grackle",
 	"kcl",
   "kcl-macros",
 ]
 
 [workspace.dependencies]
-kittycad = { version = "0.2.43", default-features = false, features = ["js"] }
+kittycad = { version = "0.2.45", default-features = false, features = ["js"] }
+kittycad-execution-plan = { git = "https://github.com/KittyCAD/modeling-api", branch = "main" }
+kittycad-execution-plan-traits = "0.1.2"
+kittycad-modeling-session = { git = "https://github.com/KittyCAD/modeling-api", branch = "main" }
+kittycad-execution-plan-macros = { git = "https://github.com/KittyCAD/modeling-api", branch = "main" }
 
 [[test]]
 name = "executor"

src/wasm-lib/grackle/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "grackle"
+version = "0.1.0"
+edition = "2021"
+description = "A new executor for KCL which compiles to Execution Plans"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+kcl-lib = { path = "../kcl" }
+kittycad-execution-plan = { workspace = true }
+kittycad-execution-plan-traits = { workspace = true }
+kittycad-modeling-session = { workspace = true }
+thiserror = "1.0.56"
+
+
+[dev-dependencies]
+pretty_assertions = "1"

src/wasm-lib/grackle/src/binding_scope.rs

@@ -0,0 +1,164 @@
+use kcl_lib::ast::types::LiteralIdentifier;
+use kcl_lib::ast::types::LiteralValue;
+
+use crate::CompileError;
+use crate::KclFunction;
+
+use super::native_functions;
+use super::Address;
+
+use std::collections::HashMap;
+
+/// KCL values which can be written to KCEP memory.
+/// This is recursive. For example, the bound value might be an array, which itself contains bound values.
+#[derive(Debug, Clone)]
+#[cfg_attr(test, derive(Eq, PartialEq))]
+pub enum EpBinding {
+    /// A KCL value which gets stored in a particular address in KCEP memory.
+    Single(Address),
+    /// A sequence of KCL values, indexed by their position in the sequence.
+    Sequence(Vec<EpBinding>),
+    /// A sequence of KCL values, indexed by their identifier.
+    Map(HashMap<String, EpBinding>),
+    /// Not associated with a KCEP address.
+    Function(KclFunction),
+}
+
+impl From<KclFunction> for EpBinding {
+    fn from(f: KclFunction) -> Self {
+        Self::Function(f)
+    }
+}
+
+impl EpBinding {
+    /// Look up the given property of this binding.
+    pub fn property_of(&self, property: LiteralIdentifier) -> Result<&Self, CompileError> {
+        match property {
+            LiteralIdentifier::Identifier(_) => todo!("Support identifier properties"),
+            LiteralIdentifier::Literal(litval) => match litval.value {
+                // Arrays can be indexed by integers.
+                LiteralValue::IInteger(i) => match self {
+                    EpBinding::Sequence(seq) => {
+                        let i = usize::try_from(i).map_err(|_| CompileError::InvalidIndex(i.to_string()))?;
+                        seq.get(i).ok_or(CompileError::IndexOutOfBounds { i, len: seq.len() })
+                    }
+                    EpBinding::Map(_) => Err(CompileError::CannotIndex),
+                    EpBinding::Single(_) => Err(CompileError::CannotIndex),
+                    EpBinding::Function(_) => Err(CompileError::CannotIndex),
+                },
+                // Objects can be indexed by string properties.
+                LiteralValue::String(property) => match self {
+                    EpBinding::Single(_) => Err(CompileError::NoProperties),
+                    EpBinding::Function(_) => Err(CompileError::NoProperties),
+                    EpBinding::Sequence(_) => Err(CompileError::ArrayDoesNotHaveProperties),
+                    EpBinding::Map(map) => map.get(&property).ok_or(CompileError::UndefinedProperty { property }),
+                },
+                // It's never valid to index by a fractional number.
+                LiteralValue::Fractional(num) => Err(CompileError::InvalidIndex(num.to_string())),
+            },
+        }
+    }
+}
+
+/// A set of bindings in a particular scope.
+/// Bindings are KCL values that get "compiled" into KCEP values, which are stored in KCEP memory
+/// at a particular KCEP address.
+/// Bindings are referenced by the name of their KCL identifier.
+///
+/// KCL has multiple scopes -- each function has a scope for its own local variables and parameters.
+/// So when referencing a variable, it might be in this scope, or the parent scope. So, each environment
+/// has to keep track of parent environments. The root environment has no parent, and is used for KCL globals
+/// (e.g. the prelude of stdlib functions).
+///
+/// These are called "Environments" in the "Crafting Interpreters" book.
+#[derive(Debug)]
+pub struct BindingScope {
+    // KCL value which are stored in EP memory.
+    ep_bindings: HashMap<String, EpBinding>,
+    /// KCL functions. They do NOT get stored in EP memory.
+    parent: Option<Box<BindingScope>>,
+}
+
+impl BindingScope {
+    /// The parent scope for every program, before the user has defined anything.
+    /// Only includes some stdlib functions.
+    /// This is usually known as the "prelude" in other languages. It's the stdlib functions that
+    /// are already imported for you when you start coding.
+    pub fn prelude() -> Self {
+        Self {
+            // TODO: Actually put the stdlib prelude in here,
+            // things like `startSketchAt` and `line`.
+            ep_bindings: HashMap::from([
+                ("id".into(), EpBinding::from(KclFunction::Id(native_functions::Id))),
+                ("add".into(), EpBinding::from(KclFunction::Add(native_functions::Add))),
+                (
+                    "startSketchAt".into(),
+                    EpBinding::from(KclFunction::StartSketchAt(native_functions::StartSketchAt)),
+                ),
+            ]),
+            parent: None,
+        }
+    }
+
+    /// Add a new scope, e.g. for new function calls.
+    pub fn add_scope(&mut self) {
+        // Move all data from `self` into `this`.
+        let this_parent = self.parent.take();
+        let this_ep_bindings = self.ep_bindings.drain().collect();
+        let this = Self {
+            ep_bindings: this_ep_bindings,
+            parent: this_parent,
+        };
+        // Turn `self` into a new scope, with the old `self` as its parent.
+        self.parent = Some(Box::new(this));
+    }
+
+    //// Remove a scope, e.g. when exiting a function call.
+    pub fn remove_scope(&mut self) {
+        // The scope is finished, so erase all its local variables.
+        self.ep_bindings.clear();
+        // Pop the stack -- the parent scope is now the current scope.
+        let p = self.parent.take().expect("cannot remove the root scope");
+        self.parent = p.parent;
+        self.ep_bindings = p.ep_bindings;
+    }
+
+    /// Add a binding (e.g. defining a new variable)
+    pub fn bind(&mut self, identifier: String, binding: EpBinding) {
+        self.ep_bindings.insert(identifier, binding);
+    }
+
+    /// Look up a binding.
+    pub fn get(&self, identifier: &str) -> Option<&EpBinding> {
+        if let Some(b) = self.ep_bindings.get(identifier) {
+            // The name was found in this scope.
+            Some(b)
+        } else if let Some(ref parent) = self.parent {
+            // Check the next scope outwards.
+            parent.get(identifier)
+        } else {
+            // There's no outer scope, and it wasn't found, so there's nowhere else to look.
+            None
+        }
+    }
+
+    /// Look up a function bound to the given identifier.
+    pub fn get_fn(&self, identifier: &str) -> GetFnResult {
+        if let Some(x) = self.get(identifier) {
+            match x {
+                EpBinding::Function(f) => GetFnResult::Found(f),
+                _ => GetFnResult::NonCallable,
+            }
+        } else if let Some(ref parent) = self.parent {
+            parent.get_fn(identifier)
+        } else {
+            GetFnResult::NotFound
+        }
+    }
+}
+
+pub enum GetFnResult<'a> {
+    Found(&'a KclFunction),
+    NonCallable,
+    NotFound,
+}

src/wasm-lib/grackle/src/error.rs

@@ -0,0 +1,56 @@
+use kcl_lib::ast::types::RequiredParamAfterOptionalParam;
+use kittycad_execution_plan::ExecutionError;
+
+use crate::String2;
+
+#[derive(Debug, thiserror::Error, PartialEq, Clone)]
+pub enum CompileError {
+    #[error("the name {name} was not defined")]
+    Undefined { name: String },
+    #[error("the function {fn_name} requires at least {required} arguments but you only supplied {actual}")]
+    NotEnoughArgs {
+        fn_name: String2,
+        required: usize,
+        actual: usize,
+    },
+    #[error("the function {fn_name} accepts at most {maximum} arguments but you supplied {actual}")]
+    TooManyArgs {
+        fn_name: String2,
+        maximum: usize,
+        actual: usize,
+    },
+    #[error("you tried to call {name} but it's not a function")]
+    NotCallable { name: String },
+    #[error("you're trying to use an operand that isn't compatible with the given arithmetic operator: {0}")]
+    InvalidOperand(&'static str),
+    #[error("you cannot use the value {0} as an index")]
+    InvalidIndex(String),
+    #[error("you tried to index into a value that isn't an array. Only arrays have numeric indices!")]
+    CannotIndex,
+    #[error("you tried to get the element {i} but that index is out of bounds. The array only has a length of {len}")]
+    IndexOutOfBounds { i: usize, len: usize },
+    #[error("you tried to access the property of a value that doesn't have any properties")]
+    NoProperties,
+    #[error("you tried to access a property of an array, but arrays don't have properties. They do have numeric indexes though, try using an index e.g. [0]")]
+    ArrayDoesNotHaveProperties,
+    #[error(
+        "you tried to read the '.{property}' of an object, but the object doesn't have any properties with that key"
+    )]
+    UndefinedProperty { property: String },
+    #[error("{0}")]
+    BadParamOrder(RequiredParamAfterOptionalParam),
+    #[error("A KCL function cannot have anything after its return value")]
+    MultipleReturns,
+    #[error("A KCL function must end with a return statement, but your function doesn't have one.")]
+    NoReturnStmt,
+    #[error("You used the %, which means \"substitute this argument for the value to the left in this |> pipeline\". But there is no such value, because you're not calling a pipeline.")]
+    NotInPipeline,
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum Error {
+    #[error("{0}")]
+    Compile(#[from] CompileError),
+    #[error("{0}")]
+    Execution(#[from] ExecutionError),
+}

src/wasm-lib/grackle/src/kcl_value_group.rs

@@ -0,0 +1,90 @@
+use kcl_lib::ast::{self, types::BinaryPart};
+
+/// Basically the same enum as `kcl_lib::ast::types::Value`, but grouped according to whether the
+/// value is singular or composite.
+/// You can convert losslessly between KclValueGroup and `kcl_lib::ast::types::Value` with From/Into.
+pub enum KclValueGroup {
+    Single(SingleValue),
+    ArrayExpression(Box<ast::types::ArrayExpression>),
+    ObjectExpression(Box<ast::types::ObjectExpression>),
+}
+
+#[derive(Debug)]
+pub enum SingleValue {
+    Literal(Box<ast::types::Literal>),
+    Identifier(Box<ast::types::Identifier>),
+    BinaryExpression(Box<ast::types::BinaryExpression>),
+    CallExpression(Box<ast::types::CallExpression>),
+    PipeExpression(Box<ast::types::PipeExpression>),
+    UnaryExpression(Box<ast::types::UnaryExpression>),
+    KclNoneExpression(ast::types::KclNone),
+    MemberExpression(Box<ast::types::MemberExpression>),
+    FunctionExpression(Box<ast::types::FunctionExpression>),
+    PipeSubstitution(Box<ast::types::PipeSubstitution>),
+}
+
+impl From<ast::types::BinaryPart> for KclValueGroup {
+    fn from(value: ast::types::BinaryPart) -> Self {
+        match value {
+            BinaryPart::Literal(e) => Self::Single(SingleValue::Literal(e)),
+            BinaryPart::Identifier(e) => Self::Single(SingleValue::Identifier(e)),
+            BinaryPart::BinaryExpression(e) => Self::Single(SingleValue::BinaryExpression(e)),
+            BinaryPart::CallExpression(e) => Self::Single(SingleValue::CallExpression(e)),
+            BinaryPart::UnaryExpression(e) => Self::Single(SingleValue::UnaryExpression(e)),
+            BinaryPart::MemberExpression(e) => Self::Single(SingleValue::MemberExpression(e)),
+        }
+    }
+}
+
+impl From<ast::types::BinaryPart> for SingleValue {
+    fn from(value: ast::types::BinaryPart) -> Self {
+        match value {
+            BinaryPart::Literal(e) => Self::Literal(e),
+            BinaryPart::Identifier(e) => Self::Identifier(e),
+            BinaryPart::BinaryExpression(e) => Self::BinaryExpression(e),
+            BinaryPart::CallExpression(e) => Self::CallExpression(e),
+            BinaryPart::UnaryExpression(e) => Self::UnaryExpression(e),
+            BinaryPart::MemberExpression(e) => Self::MemberExpression(e),
+        }
+    }
+}
+
+impl From<ast::types::Value> for KclValueGroup {
+    fn from(value: ast::types::Value) -> Self {
+        match value {
+            ast::types::Value::Literal(e) => Self::Single(SingleValue::Literal(e)),
+            ast::types::Value::Identifier(e) => Self::Single(SingleValue::Identifier(e)),
+            ast::types::Value::BinaryExpression(e) => Self::Single(SingleValue::BinaryExpression(e)),
+            ast::types::Value::CallExpression(e) => Self::Single(SingleValue::CallExpression(e)),
+            ast::types::Value::PipeExpression(e) => Self::Single(SingleValue::PipeExpression(e)),
+            ast::types::Value::None(e) => Self::Single(SingleValue::KclNoneExpression(e)),
+            ast::types::Value::UnaryExpression(e) => Self::Single(SingleValue::UnaryExpression(e)),
+            ast::types::Value::ArrayExpression(e) => Self::ArrayExpression(e),
+            ast::types::Value::ObjectExpression(e) => Self::ObjectExpression(e),
+            ast::types::Value::MemberExpression(e) => Self::Single(SingleValue::MemberExpression(e)),
+            ast::types::Value::FunctionExpression(e) => Self::Single(SingleValue::FunctionExpression(e)),
+            ast::types::Value::PipeSubstitution(e) => Self::Single(SingleValue::PipeSubstitution(e)),
+        }
+    }
+}
+
+impl From<KclValueGroup> for ast::types::Value {
+    fn from(value: KclValueGroup) -> Self {
+        match value {
+            KclValueGroup::Single(e) => match e {
+                SingleValue::Literal(e) => ast::types::Value::Literal(e),
+                SingleValue::Identifier(e) => ast::types::Value::Identifier(e),
+                SingleValue::BinaryExpression(e) => ast::types::Value::BinaryExpression(e),
+                SingleValue::CallExpression(e) => ast::types::Value::CallExpression(e),
+                SingleValue::PipeExpression(e) => ast::types::Value::PipeExpression(e),
+                SingleValue::UnaryExpression(e) => ast::types::Value::UnaryExpression(e),
+                SingleValue::KclNoneExpression(e) => ast::types::Value::None(e),
+                SingleValue::MemberExpression(e) => ast::types::Value::MemberExpression(e),
+                SingleValue::FunctionExpression(e) => ast::types::Value::FunctionExpression(e),
+                SingleValue::PipeSubstitution(e) => ast::types::Value::PipeSubstitution(e),
+            },
+            KclValueGroup::ArrayExpression(e) => ast::types::Value::ArrayExpression(e),
+            KclValueGroup::ObjectExpression(e) => ast::types::Value::ObjectExpression(e),
+        }
+    }
+}

src/wasm-lib/grackle/src/lib.rs

@@ -0,0 +1,594 @@
+mod binding_scope;
+mod error;
+mod kcl_value_group;
+mod native_functions;
+#[cfg(test)]
+mod tests;
+
+use std::collections::HashMap;
+
+use kcl_lib::{
+    ast,
+    ast::types::{BodyItem, FunctionExpressionParts, KclNone, LiteralValue, Program},
+};
+use kittycad_execution_plan as ep;
+use kittycad_execution_plan::{Address, Instruction};
+use kittycad_execution_plan_traits as ept;
+use kittycad_execution_plan_traits::NumericPrimitive;
+use kittycad_modeling_session::Session;
+
+use self::binding_scope::{BindingScope, EpBinding, GetFnResult};
+use self::error::{CompileError, Error};
+use self::kcl_value_group::{KclValueGroup, SingleValue};
+
+/// Execute a KCL program by compiling into an execution plan, then running that.
+pub async fn execute(ast: Program, session: Session) -> Result<(), Error> {
+    let mut planner = Planner::new();
+    let (plan, _retval) = planner.build_plan(ast)?;
+    let mut mem = kittycad_execution_plan::Memory::default();
+    kittycad_execution_plan::execute(&mut mem, plan, session).await?;
+    Ok(())
+}
+
+/// Compiles KCL programs into Execution Plans.
+struct Planner {
+    /// Maps KCL identifiers to what they hold, and where in KCEP virtual memory they'll be written to.
+    binding_scope: BindingScope,
+    /// Next available KCEP virtual machine memory address.
+    next_addr: Address,
+}
+
+impl Planner {
+    pub fn new() -> Self {
+        Self {
+            binding_scope: BindingScope::prelude(),
+            next_addr: Address::ZERO,
+        }
+    }
+
+    /// If successful, return the KCEP instructions for executing the given program.
+    /// If the program is a function with a return, then it also returns the KCL function's return value.
+    fn build_plan(&mut self, program: Program) -> Result<(Vec<Instruction>, Option<EpBinding>), CompileError> {
+        program
+            .body
+            .into_iter()
+            .try_fold((Vec::new(), None), |(mut instructions, mut retval), item| {
+                if retval.is_some() {
+                    return Err(CompileError::MultipleReturns);
+                }
+                let mut ctx = Context::default();
+                let instructions_for_this_node = match item {
+                    BodyItem::ExpressionStatement(node) => match KclValueGroup::from(node.expression) {
+                        KclValueGroup::Single(value) => self.plan_to_compute_single(&mut ctx, value)?.instructions,
+                        KclValueGroup::ArrayExpression(_) => todo!(),
+                        KclValueGroup::ObjectExpression(_) => todo!(),
+                    },
+                    BodyItem::VariableDeclaration(node) => self.plan_to_bind(node)?,
+                    BodyItem::ReturnStatement(node) => match KclValueGroup::from(node.argument) {
+                        KclValueGroup::Single(value) => {
+                            let EvalPlan { instructions, binding } = self.plan_to_compute_single(&mut ctx, value)?;
+                            retval = Some(binding);
+                            instructions
+                        }
+                        KclValueGroup::ArrayExpression(_) => todo!(),
+                        KclValueGroup::ObjectExpression(_) => todo!(),
+                    },
+                };
+                instructions.extend(instructions_for_this_node);
+                Ok((instructions, retval))
+            })
+    }
+
+    /// Emits instructions which, when run, compute a given KCL value and store it in memory.
+    /// Returns the instructions, and the destination address of the value.
+    fn plan_to_compute_single(&mut self, ctx: &mut Context, value: SingleValue) -> Result<EvalPlan, CompileError> {
+        match value {
+            SingleValue::KclNoneExpression(KclNone { start: _, end: _ }) => {
+                let address = self.next_addr.offset_by(1);
+                Ok(EvalPlan {
+                    instructions: vec![Instruction::SetPrimitive {
+                        address,
+                        value: ept::Primitive::Nil,
+                    }],
+                    binding: EpBinding::Single(address),
+                })
+            }
+            SingleValue::FunctionExpression(expr) => {
+                let FunctionExpressionParts {
+                    start: _,
+                    end: _,
+                    params_required,
+                    params_optional,
+                    body,
+                } = expr.into_parts().map_err(CompileError::BadParamOrder)?;
+                Ok(EvalPlan {
+                    instructions: Vec::new(),
+                    binding: EpBinding::from(KclFunction::UserDefined(UserDefinedFunction {
+                        params_optional,
+                        params_required,
+                        body,
+                    })),
+                })
+            }
+            SingleValue::Literal(expr) => {
+                let kcep_val = kcl_literal_to_kcep_literal(expr.value);
+                // KCEP primitives always have size of 1, because each address holds 1 primitive.
+                let size = 1;
+                let address = self.next_addr.offset_by(size);
+                Ok(EvalPlan {
+                    instructions: vec![Instruction::SetPrimitive {
+                        address,
+                        value: kcep_val,
+                    }],
+                    binding: EpBinding::Single(address),
+                })
+            }
+            SingleValue::Identifier(expr) => {
+                // The KCL parser interprets bools as identifiers.
+                // Consider changing them to be KCL literals instead.
+                let b = if expr.name == "true" {
+                    Some(true)
+                } else if expr.name == "false" {
+                    Some(false)
+                } else {
+                    None
+                };
+                if let Some(b) = b {
+                    let address = self.next_addr.offset_by(1);
+                    return Ok(EvalPlan {
+                        instructions: vec![Instruction::SetPrimitive {
+                            address,
+                            value: ept::Primitive::Bool(b),
+                        }],
+                        binding: EpBinding::Single(address),
+                    });
+                }
+
+                // This identifier is just duplicating a binding.
+                // So, don't emit any instructions, because the value has already been computed.
+                // Just return the address that it was stored at after being computed.
+                let previously_bound_to = self
+                    .binding_scope
+                    .get(&expr.name)
+                    .ok_or(CompileError::Undefined { name: expr.name })?;
+                Ok(EvalPlan {
+                    instructions: Vec::new(),
+                    binding: previously_bound_to.clone(),
+                })
+            }
+            SingleValue::UnaryExpression(expr) => {
+                let operand = self.plan_to_compute_single(ctx, SingleValue::from(expr.argument))?;
+                let EpBinding::Single(binding) = operand.binding else {
+                    return Err(CompileError::InvalidOperand(
+                        "you tried to use a composite value (e.g. array or object) as the operand to some math",
+                    ));
+                };
+                let destination = self.next_addr.offset_by(1);
+                let mut plan = operand.instructions;
+                plan.push(Instruction::UnaryArithmetic {
+                    arithmetic: ep::UnaryArithmetic {
+                        operation: match expr.operator {
+                            ast::types::UnaryOperator::Neg => ep::UnaryOperation::Neg,
+                            ast::types::UnaryOperator::Not => ep::UnaryOperation::Not,
+                        },
+                        operand: ep::Operand::Reference(binding),
+                    },
+                    destination,
+                });
+                Ok(EvalPlan {
+                    instructions: plan,
+                    binding: EpBinding::Single(destination),
+                })
+            }
+            SingleValue::BinaryExpression(expr) => {
+                let l = self.plan_to_compute_single(ctx, SingleValue::from(expr.left))?;
+                let r = self.plan_to_compute_single(ctx, SingleValue::from(expr.right))?;
+                let EpBinding::Single(l_binding) = l.binding else {
+                    return Err(CompileError::InvalidOperand(
+                        "you tried to use a composite value (e.g. array or object) as the operand to some math",
+                    ));
+                };
+                let EpBinding::Single(r_binding) = r.binding else {
+                    return Err(CompileError::InvalidOperand(
+                        "you tried to use a composite value (e.g. array or object) as the operand to some math",
+                    ));
+                };
+                let destination = self.next_addr.offset_by(1);
+                let mut plan = Vec::with_capacity(l.instructions.len() + r.instructions.len() + 1);
+                plan.extend(l.instructions);
+                plan.extend(r.instructions);
+                plan.push(Instruction::BinaryArithmetic {
+                    arithmetic: ep::BinaryArithmetic {
+                        operation: match expr.operator {
+                            ast::types::BinaryOperator::Add => ep::BinaryOperation::Add,
+                            ast::types::BinaryOperator::Sub => ep::BinaryOperation::Sub,
+                            ast::types::BinaryOperator::Mul => ep::BinaryOperation::Mul,
+                            ast::types::BinaryOperator::Div => ep::BinaryOperation::Div,
+                            ast::types::BinaryOperator::Mod => {
+                                todo!("execution plan instruction set doesn't support Mod yet")
+                            }
+                            ast::types::BinaryOperator::Pow => {
+                                todo!("execution plan instruction set doesn't support Pow yet")
+                            }
+                        },
+                        operand0: ep::Operand::Reference(l_binding),
+                        operand1: ep::Operand::Reference(r_binding),
+                    },
+                    destination,
+                });
+                Ok(EvalPlan {
+                    instructions: plan,
+                    binding: EpBinding::Single(destination),
+                })
+            }
+            SingleValue::CallExpression(expr) => {
+                // Make a plan to compute all the arguments to this call.
+                let (mut instructions, args) = expr.arguments.into_iter().try_fold(
+                    (Vec::new(), Vec::new()),
+                    |(mut acc_instrs, mut acc_args), argument| {
+                        let EvalPlan {
+                            instructions: new_instructions,
+                            binding: arg,
+                        } = match KclValueGroup::from(argument) {
+                            KclValueGroup::Single(value) => self.plan_to_compute_single(ctx, value)?,
+                            KclValueGroup::ArrayExpression(_) => todo!(),
+                            KclValueGroup::ObjectExpression(_) => todo!(),
+                        };
+                        acc_instrs.extend(new_instructions);
+                        acc_args.push(arg);
+                        Ok((acc_instrs, acc_args))
+                    },
+                )?;
+                // Look up the function being called.
+                let callee = match self.binding_scope.get_fn(&expr.callee.name) {
+                    GetFnResult::Found(f) => f,
+                    GetFnResult::NonCallable => {
+                        return Err(CompileError::NotCallable {
+                            name: expr.callee.name.clone(),
+                        });
+                    }
+                    GetFnResult::NotFound => {
+                        return Err(CompileError::Undefined {
+                            name: expr.callee.name.clone(),
+                        })
+                    }
+                };
+
+                // Emit instructions to call that function with the given arguments.
+                use native_functions::Callable;
+                let EvalPlan {
+                    instructions: eval_instrs,
+                    binding,
+                } = match callee {
+                    KclFunction::Id(f) => f.call(&mut self.next_addr, args)?,
+                    KclFunction::StartSketchAt(f) => f.call(&mut self.next_addr, args)?,
+                    KclFunction::Add(f) => f.call(&mut self.next_addr, args)?,
+                    KclFunction::UserDefined(f) => {
+                        let UserDefinedFunction {
+                            params_optional,
+                            params_required,
+                            body: function_body,
+                        } = f.clone();
+                        let num_required_params = params_required.len();
+                        self.binding_scope.add_scope();
+
+                        // Bind the call's arguments to the names of the function's parameters.
+                        let num_actual_params = args.len();
+                        let mut arg_iter = args.into_iter();
+                        let max_params = params_required.len() + params_optional.len();
+                        if num_actual_params > max_params {
+                            return Err(CompileError::TooManyArgs {
+                                fn_name: "".into(),
+                                maximum: max_params,
+                                actual: num_actual_params,
+                            });
+                        }
+
+                        // Bind required parameters
+                        for param in params_required {
+                            let arg = arg_iter.next().ok_or(CompileError::NotEnoughArgs {
+                                fn_name: "".into(),
+                                required: num_required_params,
+                                actual: num_actual_params,
+                            })?;
+                            self.binding_scope.bind(param.identifier.name, arg);
+                        }
+
+                        // Bind optional parameters
+                        for param in params_optional {
+                            let Some(arg) = arg_iter.next() else {
+                                break;
+                            };
+                            self.binding_scope.bind(param.identifier.name, arg);
+                        }
+
+                        let (instructions, retval) = self.build_plan(function_body)?;
+                        let Some(retval) = retval else {
+                            return Err(CompileError::NoReturnStmt);
+                        };
+                        self.binding_scope.remove_scope();
+                        EvalPlan {
+                            instructions,
+                            binding: retval,
+                        }
+                    }
+                };
+
+                // Combine the "evaluate arguments" plan with the "call function" plan.
+                instructions.extend(eval_instrs);
+                Ok(EvalPlan { instructions, binding })
+            }
+            SingleValue::MemberExpression(mut expr) => {
+                let parse = move || {
+                    let mut stack = Vec::new();
+                    loop {
+                        stack.push((expr.property, expr.computed));
+                        match expr.object {
+                            ast::types::MemberObject::MemberExpression(subexpr) => {
+                                expr = subexpr;
+                            }
+                            ast::types::MemberObject::Identifier(id) => return (stack, id),
+                        }
+                    }
+                };
+                let (properties, id) = parse();
+                let name = id.name;
+                let mut binding = self.binding_scope.get(&name).ok_or(CompileError::Undefined { name })?;
+                for (property, computed) in properties {
+                    if computed {
+                        todo!("Support computed properties like '{:?}'", property);
+                    } else {
+                        binding = binding.property_of(property)?;
+                    }
+                }
+                Ok(EvalPlan {
+                    instructions: Vec::new(),
+                    binding: binding.clone(),
+                })
+            }
+            SingleValue::PipeSubstitution(_expr) => {
+                if let Some(ref binding) = ctx.pipe_substitution {
+                    Ok(EvalPlan {
+                        instructions: Vec::new(),
+                        binding: binding.clone(),
+                    })
+                } else {
+                    Err(CompileError::NotInPipeline)
+                }
+            }
+            SingleValue::PipeExpression(expr) => {
+                let mut bodies = expr.body.into_iter();
+
+                // Get the first expression (i.e. body) of the pipeline.
+                let first = bodies.next().expect("Pipe expression must have > 1 item");
+                let EvalPlan {
+                    mut instructions,
+                    binding: mut current_value,
+                } = match KclValueGroup::from(first) {
+                    KclValueGroup::Single(v) => self.plan_to_compute_single(ctx, v)?,
+                    KclValueGroup::ArrayExpression(_) => todo!(),
+                    KclValueGroup::ObjectExpression(_) => todo!(),
+                };
+
+                // Handle the remaining bodies.
+                for body in bodies {
+                    let value = match KclValueGroup::from(body) {
+                        KclValueGroup::Single(v) => v,
+                        KclValueGroup::ArrayExpression(_) => todo!(),
+                        KclValueGroup::ObjectExpression(_) => todo!(),
+                    };
+                    // This body will probably contain a % (pipe substitution character).
+                    // So it needs to know what the previous pipeline body's value is,
+                    // to replace the % with that value.
+                    ctx.pipe_substitution = Some(current_value.clone());
+                    let EvalPlan {
+                        instructions: instructions_for_this_body,
+                        binding,
+                    } = self.plan_to_compute_single(ctx, value)?;
+                    instructions.extend(instructions_for_this_body);
+                    current_value = binding;
+                }
+                // Before we return, clear the pipe substitution, because nothing outside this
+                // pipeline should be able to use it anymore.
+                ctx.pipe_substitution = None;
+                Ok(EvalPlan {
+                    instructions,
+                    binding: current_value,
+                })
+            }
+        }
+    }
+
+    /// Emits instructions which, when run, compute a given KCL value and store it in memory.
+    /// Returns the instructions.
+    /// Also binds the value to a name.
+    fn plan_to_bind(
+        &mut self,
+        declarations: ast::types::VariableDeclaration,
+    ) -> Result<Vec<Instruction>, CompileError> {
+        let mut ctx = Context::default();
+        declarations
+            .declarations
+            .into_iter()
+            .try_fold(Vec::new(), |mut acc, declaration| {
+                let (instrs, binding) = self.plan_to_bind_one(&mut ctx, declaration.init)?;
+                self.binding_scope.bind(declaration.id.name, binding);
+                acc.extend(instrs);
+                Ok(acc)
+            })
+    }
+
+    fn plan_to_bind_one(
+        &mut self,
+        ctx: &mut Context,
+        value_being_bound: ast::types::Value,
+    ) -> Result<(Vec<Instruction>, EpBinding), CompileError> {
+        match KclValueGroup::from(value_being_bound) {
+            KclValueGroup::Single(init_value) => {
+                // Simple! Just evaluate it, note where the final value will be stored in KCEP memory,
+                // and bind it to the KCL identifier.
+                let EvalPlan { instructions, binding } = self.plan_to_compute_single(ctx, init_value)?;
+                Ok((instructions, binding))
+            }
+            KclValueGroup::ArrayExpression(expr) => {
+                // First, emit a plan to compute each element of the array.
+                // Collect all the bindings from each element too.
+                let (instructions, bindings) = expr.elements.into_iter().try_fold(
+                    (Vec::new(), Vec::new()),
+                    |(mut acc_instrs, mut acc_bindings), element| {
+                        match KclValueGroup::from(element) {
+                            KclValueGroup::Single(value) => {
+                                // If this element of the array is a single value, then binding it is
+                                // straightforward -- you got a single binding, no need to change anything.
+                                let EvalPlan { instructions, binding } = self.plan_to_compute_single(ctx, value)?;
+                                acc_instrs.extend(instructions);
+                                acc_bindings.push(binding);
+                            }
+                            KclValueGroup::ArrayExpression(expr) => {
+                                // If this element of the array is _itself_ an array, then we need to
+                                // emit a plan to calculate each element of this child array.
+                                // Then we collect the child array's bindings, and bind them to one
+                                // element of the parent array.
+                                let binding = expr
+                                    .elements
+                                    .into_iter()
+                                    .try_fold(Vec::new(), |mut seq, child_element| {
+                                        let (instructions, binding) = self.plan_to_bind_one(ctx, child_element)?;
+                                        acc_instrs.extend(instructions);
+                                        seq.push(binding);
+                                        Ok(seq)
+                                    })
+                                    .map(EpBinding::Sequence)?;
+                                acc_bindings.push(binding);
+                            }
+                            KclValueGroup::ObjectExpression(expr) => {
+                                // If this element of the array is an object, then we need to
+                                // emit a plan to calculate each value of each property of the object.
+                                // Then we collect the bindings for each child value, and bind them to one
+                                // element of the parent array.
+                                let map = HashMap::with_capacity(expr.properties.len());
+                                let binding = expr
+                                    .properties
+                                    .into_iter()
+                                    .try_fold(map, |mut map, property| {
+                                        let (instructions, binding) = self.plan_to_bind_one(ctx, property.value)?;
+                                        map.insert(property.key.name, binding);
+                                        acc_instrs.extend(instructions);
+                                        Ok(map)
+                                    })
+                                    .map(EpBinding::Map)?;
+                                acc_bindings.push(binding);
+                            }
+                        };
+                        Ok((acc_instrs, acc_bindings))
+                    },
+                )?;
+                Ok((instructions, EpBinding::Sequence(bindings)))
+            }
+            KclValueGroup::ObjectExpression(expr) => {
+                // Convert the object to a sequence of key-value pairs.
+                let mut kvs = expr.properties.into_iter().map(|prop| (prop.key, prop.value));
+                let (instructions, each_property_binding) = kvs.try_fold(
+                    (Vec::new(), HashMap::new()),
+                    |(mut acc_instrs, mut acc_bindings), (key, value)| {
+                        match KclValueGroup::from(value) {
+                            KclValueGroup::Single(value) => {
+                                let EvalPlan { instructions, binding } = self.plan_to_compute_single(ctx, value)?;
+                                acc_instrs.extend(instructions);
+                                acc_bindings.insert(key.name, binding);
+                            }
+                            KclValueGroup::ArrayExpression(expr) => {
+                                // If this value of the object is an array, then emit a plan to calculate
+                                // each element of that array. Collect their bindings, and bind them all
+                                // under one property of the parent object.
+                                let n = expr.elements.len();
+                                let binding = expr
+                                    .elements
+                                    .into_iter()
+                                    .try_fold(Vec::with_capacity(n), |mut seq, child_element| {
+                                        let (instructions, binding) = self.plan_to_bind_one(ctx, child_element)?;
+                                        seq.push(binding);
+                                        acc_instrs.extend(instructions);
+                                        Ok(seq)
+                                    })
+                                    .map(EpBinding::Sequence)?;
+                                acc_bindings.insert(key.name, binding);
+                            }
+                            KclValueGroup::ObjectExpression(expr) => {
+                                // If this value of the object is _itself_ an object, then we need to
+                                // emit a plan to calculate each value of each property of the child object.
+                                // Then we collect the bindings for each child value, and bind them to one
+                                // property of the parent object.
+                                let n = expr.properties.len();
+                                let binding = expr
+                                    .properties
+                                    .into_iter()
+                                    .try_fold(HashMap::with_capacity(n), |mut map, property| {
+                                        let (instructions, binding) = self.plan_to_bind_one(ctx, property.value)?;
+                                        map.insert(property.key.name, binding);
+                                        acc_instrs.extend(instructions);
+                                        Ok(map)
+                                    })
+                                    .map(EpBinding::Map)?;
+                                acc_bindings.insert(key.name, binding);
+                            }
+                        };
+                        Ok((acc_instrs, acc_bindings))
+                    },
+                )?;
+                Ok((instructions, EpBinding::Map(each_property_binding)))
+            }
+        }
+    }
+}
+
+/// Every KCL literal value is equivalent to an Execution Plan value, and therefore can be
+/// bound to some KCL name and Execution Plan address.
+fn kcl_literal_to_kcep_literal(expr: LiteralValue) -> ept::Primitive {
+    match expr {
+        LiteralValue::IInteger(x) => ept::Primitive::NumericValue(NumericPrimitive::Integer(x)),
+        LiteralValue::Fractional(x) => ept::Primitive::NumericValue(NumericPrimitive::Float(x)),
+        LiteralValue::String(x) => ept::Primitive::String(x),
+    }
+}
+
+/// Instructions that can compute some value.
+struct EvalPlan {
+    /// The instructions which will compute the value.
+    instructions: Vec<Instruction>,
+    /// Where the value will be stored.
+    binding: EpBinding,
+}
+
+/// Either an owned string, or a static string. Either way it can be read and moved around.
+pub type String2 = std::borrow::Cow<'static, str>;
+
+#[derive(Debug, Clone)]
+struct UserDefinedFunction {
+    params_optional: Vec<ast::types::Parameter>,
+    params_required: Vec<ast::types::Parameter>,
+    body: ast::types::Program,
+}
+
+impl PartialEq for UserDefinedFunction {
+    fn eq(&self, other: &Self) -> bool {
+        self.params_optional == other.params_optional && self.params_required == other.params_required
+    }
+}
+
+impl Eq for UserDefinedFunction {}
+
+#[derive(Debug, Clone)]
+#[cfg_attr(test, derive(Eq, PartialEq))]
+enum KclFunction {
+    Id(native_functions::Id),
+    StartSketchAt(native_functions::StartSketchAt),
+    Add(native_functions::Add),
+    UserDefined(UserDefinedFunction),
+}
+
+/// Context used when compiling KCL.
+#[derive(Default, Debug)]
+struct Context {
+    pipe_substitution: Option<EpBinding>,
+}

src/wasm-lib/grackle/src/native_functions.rs

@@ -0,0 +1,112 @@
+//! Defines functions which are written in Rust, but called from KCL.
+//! This includes some of the stdlib, e.g. `startSketchAt`.
+//! But some other stdlib functions will be written in KCL.
+
+use kcl_lib::std::sketch::PlaneData;
+use kittycad_execution_plan::{Address, BinaryArithmetic, Instruction};
+use kittycad_execution_plan_traits::Value;
+
+use crate::{CompileError, EpBinding, EvalPlan};
+
+/// The identity function. Always returns its first input.
+#[derive(Debug, Clone)]
+#[cfg_attr(test, derive(Eq, PartialEq))]
+pub struct Id;
+
+pub trait Callable {
+    fn call(&self, next_addr: &mut Address, args: Vec<EpBinding>) -> Result<EvalPlan, CompileError>;
+}
+
+impl Callable for Id {
+    fn call(&self, _: &mut Address, args: Vec<EpBinding>) -> Result<EvalPlan, CompileError> {
+        if args.len() > 1 {
+            return Err(CompileError::TooManyArgs {
+                fn_name: "id".into(),
+                maximum: 1,
+                actual: args.len(),
+            });
+        }
+        let arg = args
+            .first()
+            .ok_or(CompileError::NotEnoughArgs {
+                fn_name: "id".into(),
+                required: 1,
+                actual: 0,
+            })?
+            .clone();
+        Ok(EvalPlan {
+            instructions: Vec::new(),
+            binding: arg,
+        })
+    }
+}
+
+#[derive(Debug, Clone)]
+#[cfg_attr(test, derive(Eq, PartialEq))]
+pub struct StartSketchAt;
+
+impl Callable for StartSketchAt {
+    fn call(&self, next_addr: &mut Address, _args: Vec<EpBinding>) -> Result<EvalPlan, CompileError> {
+        let mut instructions = Vec::new();
+        // Store the plane.
+        let plane = PlaneData::XY.into_parts();
+        instructions.push(Instruction::SetValue {
+            address: next_addr.offset_by(plane.len()),
+            value_parts: plane,
+        });
+        // TODO: Get the plane ID from global context.
+        // TODO: Send this command:
+        // ModelingCmd::SketchModeEnable {
+        //     animated: false,
+        //     ortho: false,
+        //     plane_id: plane.id,
+        //     // We pass in the normal for the plane here.
+        //     disable_camera_with_plane: Some(plane.z_axis.clone().into()),
+        // },
+        // TODO: Send ModelingCmd::StartPath at the given point.
+        // TODO (maybe): Store the SketchGroup in KCEP memory.
+        todo!()
+    }
+}
+
+/// A test function that adds two numbers.
+#[derive(Debug, Clone)]
+#[cfg_attr(test, derive(Eq, PartialEq))]
+pub struct Add;
+
+impl Callable for Add {
+    fn call(&self, next_address: &mut Address, mut args: Vec<EpBinding>) -> Result<EvalPlan, CompileError> {
+        let len = args.len();
+        if len > 2 {
+            return Err(CompileError::TooManyArgs {
+                fn_name: "add".into(),
+                maximum: 2,
+                actual: len,
+            });
+        }
+        let not_enough_args = CompileError::NotEnoughArgs {
+            fn_name: "add".into(),
+            required: 2,
+            actual: len,
+        };
+        const ERR: &str = "cannot use composite values (e.g. array) as arguments to Add";
+        let EpBinding::Single(arg1) = args.pop().ok_or(not_enough_args.clone())? else {
+            return Err(CompileError::InvalidOperand(ERR));
+        };
+        let EpBinding::Single(arg0) = args.pop().ok_or(not_enough_args)? else {
+            return Err(CompileError::InvalidOperand(ERR));
+        };
+        let destination = next_address.offset_by(1);
+        Ok(EvalPlan {
+            instructions: vec![Instruction::BinaryArithmetic {
+                arithmetic: BinaryArithmetic {
+                    operation: kittycad_execution_plan::BinaryOperation::Add,
+                    operand0: kittycad_execution_plan::Operand::Reference(arg0),
+                    operand1: kittycad_execution_plan::Operand::Reference(arg1),
+                },
+                destination,
+            }],
+            binding: EpBinding::Single(destination),
+        })
+    }
+}

src/wasm-lib/grackle/src/tests.rs

@@ -0,0 +1,745 @@
+use ep::UnaryArithmetic;
+use pretty_assertions::assert_eq;
+
+use super::*;
+
+fn must_plan(program: &str) -> (Vec<Instruction>, BindingScope) {
+    let tokens = kcl_lib::token::lexer(program);
+    let parser = kcl_lib::parser::Parser::new(tokens);
+    let ast = parser.ast().unwrap();
+    let mut p = Planner::new();
+    let (instrs, _) = p.build_plan(ast).unwrap();
+    (instrs, p.binding_scope)
+}
+
+fn should_not_compile(program: &str) -> CompileError {
+    let tokens = kcl_lib::token::lexer(program);
+    let parser = kcl_lib::parser::Parser::new(tokens);
+    let ast = parser.ast().unwrap();
+    let mut p = Planner::new();
+    p.build_plan(ast).unwrap_err()
+}
+
+#[test]
+fn assignments() {
+    let program = "
+        let x = 1
+        let y = 2";
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: 1i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(1),
+                value: 2i64.into(),
+            }
+        ]
+    );
+}
+
+#[test]
+fn bind_array() {
+    let program = r#"let x = [44, 55, "sixty-six"]"#;
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: 44i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(1),
+                value: 55i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(2),
+                value: "sixty-six".to_owned().into(),
+            }
+        ]
+    );
+}
+
+#[test]
+fn bind_nested_array() {
+    let program = r#"let x = [44, [55, "sixty-six"]]"#;
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: 44i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(1),
+                value: 55i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(2),
+                value: "sixty-six".to_owned().into(),
+            }
+        ]
+    );
+}
+
+#[test]
+fn bind_arrays_with_objects_elements() {
+    let program = r#"let x = [44, {a: 55, b: "sixty-six"}]"#;
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: 44i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(1),
+                value: 55i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(2),
+                value: "sixty-six".to_owned().into(),
+            }
+        ]
+    );
+}
+
+#[test]
+fn statement_after_return() {
+    let program = "fn f = () => {
+        return 1
+        let x = 2
+    }
+    f()";
+    let err = should_not_compile(program);
+    assert_eq!(err, CompileError::MultipleReturns);
+}
+
+#[test]
+fn name_not_found() {
+    // Users can't assign `y` to anything because `y` is undefined.
+    let err = should_not_compile("let x = y");
+    assert_eq!(err, CompileError::Undefined { name: "y".to_owned() });
+}
+
+#[test]
+fn assign_bool() {
+    // Check that Grackle properly compiles KCL bools to EP bools.
+    for (str, val) in [("true", true), ("false", false)] {
+        let program = format!("let x = {str}");
+        let (plan, scope) = must_plan(&program);
+        assert_eq!(
+            plan,
+            vec![Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: val.into(),
+            }]
+        );
+        assert_eq!(scope.get("x"), Some(&EpBinding::Single(Address::ZERO)));
+    }
+}
+
+#[test]
+fn aliases() {
+    let program = "
+        let x = 1
+        let y = x";
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 1i64.into(),
+        }]
+    );
+}
+
+#[test]
+fn use_native_function_add() {
+    let program = "let x = add(1,2)";
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: 1i64.into()
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(1),
+                value: 2i64.into()
+            },
+            Instruction::BinaryArithmetic {
+                arithmetic: ep::BinaryArithmetic {
+                    operation: ep::BinaryOperation::Add,
+                    operand0: ep::Operand::Reference(Address::ZERO),
+                    operand1: ep::Operand::Reference(Address::ZERO.offset(1))
+                },
+                destination: Address::ZERO.offset(2),
+            }
+        ]
+    );
+}
+
+#[test]
+fn use_native_function_id() {
+    let program = "let x = id(2)";
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 2i64.into()
+        }]
+    );
+}
+
+#[test]
+#[ignore = "haven't done computed properties yet"]
+fn computed_array_index() {
+    let program = r#"
+    let array = ["a", "b", "c"]
+    let index = 1+1
+    let prop = array[index]
+    "#;
+    let (_plan, scope) = must_plan(program);
+    match scope.get("prop").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(*addr, Address::ZERO + 1);
+        }
+        other => {
+            panic!("expected 'prop' bound to 0x0 but it was bound to {other:?}");
+        }
+    }
+}
+
+#[test]
+#[ignore = "haven't done computed properties yet"]
+fn computed_member_expressions() {
+    let program = r#"
+    let obj = {x: 1, y: 2}
+    let index = "x"
+    let prop = obj[index]
+    "#;
+    let (_plan, scope) = must_plan(program);
+    match scope.get("prop").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(*addr, Address::ZERO + 1);
+        }
+        other => {
+            panic!("expected 'prop' bound to 0x0 but it was bound to {other:?}");
+        }
+    }
+}
+
+#[test]
+fn member_expressions_object() {
+    let program = r#"
+    let obj = {x: 1, y: 2}
+    let prop = obj["y"]
+    "#;
+    let (_plan, scope) = must_plan(program);
+    match scope.get("prop").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(*addr, Address::ZERO + 1);
+        }
+        other => {
+            panic!("expected 'prop' bound to 0x0 but it was bound to {other:?}");
+        }
+    }
+}
+
+#[test]
+fn member_expressions_array() {
+    let program = "
+    let array = [[1,2],[3,4]]
+    let first = array[0][0]
+    let last = array[1][1]
+    ";
+    let (_plan, scope) = must_plan(program);
+    match scope.get("first").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(*addr, Address::ZERO);
+        }
+        other => {
+            panic!("expected 'number' bound to 0x0 but it was bound to {other:?}");
+        }
+    }
+    match scope.get("last").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(*addr, Address::ZERO + 3);
+        }
+        other => {
+            panic!("expected 'number' bound to 0x3 but it was bound to {other:?}");
+        }
+    }
+}
+
+#[test]
+fn compile_flipped_sign() {
+    let program = "let x = 3
+    let y = -x";
+    let (plan, _scope) = must_plan(program);
+    let expected = vec![
+        Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 3i64.into(),
+        },
+        Instruction::UnaryArithmetic {
+            arithmetic: UnaryArithmetic {
+                operation: ep::UnaryOperation::Neg,
+                operand: ep::Operand::Reference(Address::ZERO),
+            },
+            destination: Address::ZERO + 1,
+        },
+    ];
+    assert_eq!(plan, expected);
+}
+
+#[test]
+fn add_literals() {
+    let program = "let x = 1 + 2";
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: Address::ZERO,
+                value: 1i64.into()
+            },
+            Instruction::SetPrimitive {
+                address: Address::ZERO.offset(1),
+                value: 2i64.into()
+            },
+            Instruction::BinaryArithmetic {
+                arithmetic: ep::BinaryArithmetic {
+                    operation: ep::BinaryOperation::Add,
+                    operand0: ep::Operand::Reference(Address::ZERO),
+                    operand1: ep::Operand::Reference(Address::ZERO.offset(1)),
+                },
+                destination: Address::ZERO.offset(2),
+            }
+        ]
+    );
+}
+
+#[test]
+fn add_vars() {
+    let program = "
+        let one = 1
+        let two = 2
+        let x = one + two";
+    let (plan, _bindings) = must_plan(program);
+    let addr0 = Address::ZERO;
+    let addr1 = Address::ZERO.offset(1);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: addr0,
+                value: 1i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: addr1,
+                value: 2i64.into(),
+            },
+            Instruction::BinaryArithmetic {
+                arithmetic: ep::BinaryArithmetic {
+                    operation: ep::BinaryOperation::Add,
+                    operand0: ep::Operand::Reference(addr0),
+                    operand1: ep::Operand::Reference(addr1),
+                },
+                destination: Address::ZERO.offset(2),
+            }
+        ]
+    );
+}
+
+#[test]
+fn composite_binary_exprs() {
+    let program = "
+        let x = 1
+        let y = 2
+        let z = 3
+        let six = x + y + z
+        ";
+    let (plan, _bindings) = must_plan(program);
+    let addr0 = Address::ZERO;
+    let addr1 = Address::ZERO.offset(1);
+    let addr2 = Address::ZERO.offset(2);
+    let addr3 = Address::ZERO.offset(3);
+    assert_eq!(
+        plan,
+        vec![
+            Instruction::SetPrimitive {
+                address: addr0,
+                value: 1i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: addr1,
+                value: 2i64.into(),
+            },
+            Instruction::SetPrimitive {
+                address: addr2,
+                value: 3i64.into(),
+            },
+            // Adds 1 + 2
+            Instruction::BinaryArithmetic {
+                arithmetic: ep::BinaryArithmetic {
+                    operation: ep::BinaryOperation::Add,
+                    operand0: ep::Operand::Reference(addr0),
+                    operand1: ep::Operand::Reference(addr1),
+                },
+                destination: addr3,
+            },
+            // Adds `x` + 3, where `x` is (1 + 2)
+            Instruction::BinaryArithmetic {
+                arithmetic: ep::BinaryArithmetic {
+                    operation: ep::BinaryOperation::Add,
+                    operand0: ep::Operand::Reference(addr3),
+                    operand1: ep::Operand::Reference(addr2),
+                },
+                destination: Address::ZERO.offset(4),
+            }
+        ]
+    );
+}
+
+#[test]
+fn use_kcl_functions_zero_params() {
+    let (plan, scope) = must_plan(
+        "fn triple = () => { return 123 }
+    let x = triple()",
+    );
+    assert_eq!(
+        plan,
+        vec![Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 123i64.into()
+        }]
+    );
+    match scope.get("x").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(addr, &Address::ZERO);
+        }
+        other => {
+            panic!("expected 'x' bound to an address but it was bound to {other:?}");
+        }
+    }
+}
+
+#[test]
+fn use_kcl_functions_with_optional_params() {
+    for (i, program) in ["fn triple = (x, y?) => { return x*3 }
+    let x = triple(1, 888)"]
+    .into_iter()
+    .enumerate()
+    {
+        let (plan, scope) = must_plan(program);
+        let destination = Address::ZERO + 3;
+        assert_eq!(
+            plan,
+            vec![
+                Instruction::SetPrimitive {
+                    address: Address::ZERO,
+                    value: 1i64.into(),
+                },
+                Instruction::SetPrimitive {
+                    address: Address::ZERO + 1,
+                    value: 888i64.into(),
+                },
+                Instruction::SetPrimitive {
+                    address: Address::ZERO + 2,
+                    value: 3i64.into(),
+                },
+                Instruction::BinaryArithmetic {
+                    arithmetic: ep::BinaryArithmetic {
+                        operation: ep::BinaryOperation::Mul,
+                        operand0: ep::Operand::Reference(Address::ZERO),
+                        operand1: ep::Operand::Reference(Address::ZERO + 2)
+                    },
+                    destination,
+                }
+            ],
+            "failed test {i}"
+        );
+        match scope.get("x").unwrap() {
+            EpBinding::Single(addr) => {
+                assert_eq!(addr, &destination, "failed test {i}");
+            }
+            other => {
+                panic!("expected 'x' bound to an address but it was bound to {other:?}, so failed test {i}");
+            }
+        }
+    }
+}
+
+#[test]
+fn use_kcl_functions_with_too_many_params() {
+    let program = "fn triple = (x, y?) => { return x*3 }
+    let x = triple(1, 2, 3)";
+    let err = should_not_compile(program);
+    assert!(matches!(
+        err,
+        CompileError::TooManyArgs {
+            maximum: 2,
+            actual: 3,
+            ..
+        }
+    ))
+}
+
+#[test]
+fn use_kcl_function_as_return_value() {
+    let program = "fn twotwotwo = () => {
+            return () => { return 222 }
+        }
+        let f = twotwotwo()
+        let x = f()";
+    let (plan, scope) = must_plan(program);
+    match scope.get("x").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(addr, &Address::ZERO);
+        }
+        other => {
+            panic!("expected 'x' bound to an address but it was bound to {other:?}, so failed test");
+        }
+    }
+    assert_eq!(
+        plan,
+        vec![Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 222i64.into()
+        }]
+    )
+}
+
+#[test]
+fn define_recursive_function() {
+    let program = "fn add_infinitely = (i) => {
+            return add_infinitely(i+1)
+        }";
+    let (plan, _scope) = must_plan(program);
+    assert_eq!(plan, Vec::new())
+}
+#[test]
+fn use_kcl_function_as_param() {
+    let program = "fn wrapper = (f) => {
+            return f()
+        }
+        fn twotwotwo = () => { 
+            return 222
+        }
+        let x = wrapper(twotwotwo)";
+    let (plan, scope) = must_plan(program);
+    match scope.get("x").unwrap() {
+        EpBinding::Single(addr) => {
+            assert_eq!(addr, &Address::ZERO);
+        }
+        other => {
+            panic!("expected 'x' bound to an address but it was bound to {other:?}, so failed test");
+        }
+    }
+    assert_eq!(
+        plan,
+        vec![Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 222i64.into()
+        }]
+    )
+}
+
+#[test]
+fn use_kcl_functions_with_params() {
+    for (i, program) in [
+        "fn triple = (x) => { return x*3 }
+    let x = triple(1)",
+        "fn triple = (x,y?) => { return x*3 }
+    let x = triple(1)",
+    ]
+    .into_iter()
+    .enumerate()
+    {
+        let (plan, scope) = must_plan(program);
+        let destination = Address::ZERO + 2;
+        assert_eq!(
+            plan,
+            vec![
+                Instruction::SetPrimitive {
+                    address: Address::ZERO,
+                    value: 1i64.into(),
+                },
+                Instruction::SetPrimitive {
+                    address: Address::ZERO + 1,
+                    value: 3i64.into(),
+                },
+                Instruction::BinaryArithmetic {
+                    arithmetic: ep::BinaryArithmetic {
+                        operation: ep::BinaryOperation::Mul,
+                        operand0: ep::Operand::Reference(Address::ZERO),
+                        operand1: ep::Operand::Reference(Address::ZERO.offset(1))
+                    },
+                    destination,
+                }
+            ],
+            "failed test {i}"
+        );
+        match scope.get("x").unwrap() {
+            EpBinding::Single(addr) => {
+                assert_eq!(addr, &destination, "failed test {i}");
+            }
+            other => {
+                panic!("expected 'x' bound to an address but it was bound to {other:?}, so failed test {i}");
+            }
+        }
+    }
+}
+
+#[test]
+fn pipe_substitution_outside_pipe_expression() {
+    let program = "let x = add(1, %)";
+    let err = should_not_compile(program);
+    assert!(matches!(err, CompileError::NotInPipeline));
+}
+
+#[test]
+fn unsugar_pipe_expressions() {
+    // These two programs should be equivalent,
+    // because that's just the definition of the |> operator.
+    let program2 = "
+    fn double = (x) => { return x * 2 }
+    fn triple = (x) => { return x * 3 }
+    let x = 1 |> double(%) |> triple(%) // should be 6
+    ";
+    let program1 = "
+    fn double = (x) => { return x * 2 }
+    fn triple = (x) => { return x * 3 }
+    let x = triple(double(1)) // should be 6
+    ";
+    // So, check that they are.
+    let (plan1, _) = must_plan(program1);
+    let (plan2, _) = must_plan(program2);
+    assert_eq!(plan1, plan2);
+}
+
+#[test]
+fn define_kcl_functions() {
+    let (plan, scope) = must_plan("fn triple = (x) => { return x * 3 }");
+    assert!(plan.is_empty());
+    match scope.get("triple").unwrap() {
+        EpBinding::Function(KclFunction::UserDefined(expr)) => {
+            assert!(expr.params_optional.is_empty());
+            assert_eq!(expr.params_required.len(), 1);
+        }
+        other => {
+            panic!("expected 'triple' bound to a user-defined KCL function but it was bound to {other:?}");
+        }
+    }
+}
+
+#[test]
+fn aliases_dont_affect_plans() {
+    let (plan1, _) = must_plan(
+        "let one = 1
+            let two = 2
+            let x = one + two",
+    );
+    let (plan2, _) = must_plan(
+        "let one = 1
+            let two = 2
+            let y = two
+            let x = one + y",
+    );
+    assert_eq!(plan1, plan2);
+}
+
+#[test]
+fn store_object() {
+    let program = "const x0 = {a: 1, b: 2, c: {d: 3}}";
+    let (actual, bindings) = must_plan(program);
+    let expected = vec![
+        Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 1i64.into(),
+        },
+        Instruction::SetPrimitive {
+            address: Address::ZERO.offset(1),
+            value: 2i64.into(),
+        },
+        Instruction::SetPrimitive {
+            address: Address::ZERO.offset(2),
+            value: 3i64.into(),
+        },
+    ];
+    assert_eq!(actual, expected);
+    eprintln!("{bindings:#?}");
+    assert_eq!(
+        bindings.get("x0").unwrap(),
+        &EpBinding::Map(HashMap::from([
+            ("a".to_owned(), EpBinding::Single(Address::ZERO),),
+            ("b".to_owned(), EpBinding::Single(Address::ZERO.offset(1))),
+            (
+                "c".to_owned(),
+                EpBinding::Map(HashMap::from([(
+                    "d".to_owned(),
+                    EpBinding::Single(Address::ZERO.offset(2))
+                )]))
+            ),
+        ]))
+    )
+}
+
+#[test]
+fn store_object_with_array_property() {
+    let program = "const x0 = {a: 1, b: [2, 3]}";
+    let (actual, bindings) = must_plan(program);
+    let expected = vec![
+        Instruction::SetPrimitive {
+            address: Address::ZERO,
+            value: 1i64.into(),
+        },
+        Instruction::SetPrimitive {
+            address: Address::ZERO.offset(1),
+            value: 2i64.into(),
+        },
+        Instruction::SetPrimitive {
+            address: Address::ZERO.offset(2),
+            value: 3i64.into(),
+        },
+    ];
+    assert_eq!(actual, expected);
+    eprintln!("{bindings:#?}");
+    assert_eq!(
+        bindings.get("x0").unwrap(),
+        &EpBinding::Map(HashMap::from([
+            ("a".to_owned(), EpBinding::Single(Address::ZERO),),
+            (
+                "b".to_owned(),
+                EpBinding::Sequence(vec![
+                    EpBinding::Single(Address::ZERO.offset(1)),
+                    EpBinding::Single(Address::ZERO.offset(2)),
+                ])
+            ),
+        ]))
+    )
+}
+
+#[ignore = "haven't done API calls or stdlib yet"]
+#[test]
+fn stdlib_api_calls() {
+    let program = "const x0 = startSketchAt([0, 0])
+        const x1 = line([0, 10], x0)
+        const x2 = line([10, 0], x1)
+        const x3 = line([0, -10], x2)
+        const x4 = line([0, 0], x3)
+        const x5 = close(x4)
+        const x6 = extrude(20, x5)
+      show(x6)";
+    must_plan(program);
+}

src/wasm-lib/kcl/Cargo.toml

@@ -21,15 +21,18 @@ databake = { version = "0.1.7", features = ["derive"] }
 derive-docs = { version = "0.1.5" }
 # derive-docs = { path = "../derive-docs" }
 kittycad = { workspace = true }
+kittycad-execution-plan-macros = { workspace = true }
+kittycad-execution-plan-traits = { workspace = true }
 lazy_static = "1.4.0"
 parse-display = "0.8.2"
 schemars = { version = "0.8.16", features = ["impl_json_schema", "url", "uuid1"] }
 serde = { version = "1.0.193", features = ["derive"] }
 serde_json = "1.0.108"
 thiserror = "1.0.50"
-ts-rs = { version = "7", package = "ts-rs-json-value", features = ["serde-json-impl", "schemars-impl", "uuid-impl"] }
+ts-rs = { version = "7", features = ["uuid-impl"] }
 uuid = { version = "1.6.1", features = ["v4", "js", "serde"] }
 winnow = "0.5.18"
+either = "1.6.1"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 js-sys = { version = "0.3.65" }

src/wasm-lib/kcl/src/ast/types.rs

@@ -19,6 +19,7 @@ use crate::{
     parser::PIPE_OPERATOR,
     std::{kcl_stdlib::KclStdLibFn, FunctionKind},
 };
+use crate::executor::PathToNode;
 
 mod literal_value;
 mod none;
@@ -1433,6 +1434,7 @@ impl From<Literal> for MemoryItem {
             value: JValue::from(literal.value.clone()),
             meta: vec![Metadata {
                 source_range: literal.into(),
+                path_to_node: vec![],
             }],
         })
     }
@@ -1444,6 +1446,7 @@ impl From<&Box<Literal>> for MemoryItem {
             value: JValue::from(literal.value.clone()),
             meta: vec![Metadata {
                 source_range: literal.into(),
+                path_to_node: vec![],
             }],
         })
     }
@@ -1641,7 +1644,7 @@ impl ArrayExpression {
                 Value::UnaryExpression(unary_expression) => unary_expression.get_result(memory, pipe_info, ctx).await?,
                 Value::ObjectExpression(object_expression) => object_expression.execute(memory, pipe_info, ctx).await?,
                 Value::ArrayExpression(array_expression) => array_expression.execute(memory, pipe_info, ctx).await?,
-                Value::PipeExpression(pipe_expression) => pipe_expression.get_result(memory, pipe_info, ctx).await?,
+                Value::PipeExpression(pipe_expression) => pipe_expression.get_result(memory, pipe_info, ctx, vec![]).await?,
                 Value::PipeSubstitution(pipe_substitution) => {
                     return Err(KclError::Semantic(KclErrorDetails {
                         message: format!("PipeSubstitution not implemented here: {:?}", pipe_substitution),
@@ -1665,6 +1668,7 @@ impl ArrayExpression {
             value: results.into(),
             meta: vec![Metadata {
                 source_range: self.into(),
+                path_to_node: vec![],
             }],
         }))
     }
@@ -1794,7 +1798,7 @@ impl ObjectExpression {
                 Value::UnaryExpression(unary_expression) => unary_expression.get_result(memory, pipe_info, ctx).await?,
                 Value::ObjectExpression(object_expression) => object_expression.execute(memory, pipe_info, ctx).await?,
                 Value::ArrayExpression(array_expression) => array_expression.execute(memory, pipe_info, ctx).await?,
-                Value::PipeExpression(pipe_expression) => pipe_expression.get_result(memory, pipe_info, ctx).await?,
+                Value::PipeExpression(pipe_expression) => pipe_expression.get_result(memory, pipe_info, ctx, vec![]).await?,
                 Value::PipeSubstitution(pipe_substitution) => {
                     return Err(KclError::Semantic(KclErrorDetails {
                         message: format!("PipeSubstitution not implemented here: {:?}", pipe_substitution),
@@ -1822,6 +1826,7 @@ impl ObjectExpression {
             value: object.into(),
             meta: vec![Metadata {
                 source_range: self.into(),
+                path_to_node: vec![],
             }],
         }))
     }
@@ -2031,6 +2036,7 @@ impl MemberExpression {
                     value: value.clone(),
                     meta: vec![Metadata {
                         source_range: self.into(),
+                        path_to_node: vec![],
                     }],
                 }))
             } else {
@@ -2087,6 +2093,7 @@ impl MemberExpression {
                     value: value.clone(),
                     meta: vec![Metadata {
                         source_range: self.into(),
+                        path_to_node: vec![],
                     }],
                 }))
             } else {
@@ -2251,6 +2258,7 @@ impl BinaryExpression {
                     value,
                     meta: vec![Metadata {
                         source_range: self.into(),
+                        path_to_node: vec![],
                     }],
                 }));
             }
@@ -2272,6 +2280,7 @@ impl BinaryExpression {
             value,
             meta: vec![Metadata {
                 source_range: self.into(),
+                path_to_node: vec![],
             }],
         }))
     }
@@ -2435,6 +2444,7 @@ impl UnaryExpression {
             value: (-(num)).into(),
             meta: vec![Metadata {
                 source_range: self.into(),
+                path_to_node: vec![],
             }],
         }))
     }
@@ -2564,11 +2574,12 @@ impl PipeExpression {
         memory: &mut ProgramMemory,
         pipe_info: &mut PipeInfo,
         ctx: &ExecutorContext,
+        path_to_node: PathToNode,
     ) -> Result<MemoryItem, KclError> {
         // Reset the previous results.
         pipe_info.previous_results = vec![];
         pipe_info.index = 0;
-        execute_pipe_body(memory, &self.body, pipe_info, self.into(), ctx).await
+        execute_pipe_body(memory, &self.body, pipe_info, self.into(), ctx, path_to_node).await
     }
 
     /// Rename all identifiers that have the old name to the new given name.
@@ -2586,6 +2597,8 @@ async fn execute_pipe_body(
     pipe_info: &mut PipeInfo,
     source_range: SourceRange,
     ctx: &ExecutorContext,
+    path_to_node: PathToNode,
+    
 ) -> Result<MemoryItem, KclError> {
     if pipe_info.index == body.len() {
         pipe_info.is_in_pipe = false;
@@ -2631,7 +2644,7 @@ async fn execute_pipe_body(
 }
 
 /// Parameter of a KCL function.
-#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, ts_rs::TS, JsonSchema, Bake)]
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, Eq, ts_rs::TS, JsonSchema, Bake)]
 #[databake(path = kcl_lib::ast::types)]
 #[ts(export)]
 #[serde(tag = "type")]
@@ -2655,6 +2668,23 @@ pub struct FunctionExpression {
 
 impl_value_meta!(FunctionExpression);
 
+pub struct FunctionExpressionParts {
+    pub start: usize,
+    pub end: usize,
+    pub params_required: Vec<Parameter>,
+    pub params_optional: Vec<Parameter>,
+    pub body: Program,
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct RequiredParamAfterOptionalParam(pub Parameter);
+
+impl std::fmt::Display for RequiredParamAfterOptionalParam {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "KCL functions must declare any optional parameters after all the required parameters. But your required parameter {} is _after_ an optional parameter. You must move it to before the optional parameters instead.", self.0.identifier.name)
+    }
+}
+
 impl FunctionExpression {
     /// Function expressions don't really apply.
     pub fn get_constraint_level(&self) -> ConstraintLevel {
@@ -2663,6 +2693,36 @@ impl FunctionExpression {
         }
     }
 
+    pub fn into_parts(self) -> Result<FunctionExpressionParts, RequiredParamAfterOptionalParam> {
+        let Self {
+            start,
+            end,
+            params,
+            body,
+        } = self;
+        let mut params_required = Vec::with_capacity(params.len());
+        let mut params_optional = Vec::with_capacity(params.len());
+        for param in params {
+            if param.optional {
+                params_optional.push(param);
+            } else {
+                if !params_optional.is_empty() {
+                    return Err(RequiredParamAfterOptionalParam(param));
+                }
+                params_required.push(param);
+            }
+        }
+        params_required.shrink_to_fit();
+        params_optional.shrink_to_fit();
+        Ok(FunctionExpressionParts {
+            start,
+            end,
+            params_required,
+            params_optional,
+            body,
+        })
+    }
+
     /// Required parameters must be declared before optional parameters.
     /// This gets all the required parameters.
     pub fn required_params(&self) -> &[Parameter] {

src/wasm-lib/kcl/src/docs.rs

@@ -42,6 +42,7 @@ pub struct StdLibFnArg {
     /// The type of the argument.
     pub type_: String,
     /// The schema of the argument.
+    #[ts(type = "any")]
     pub schema: schemars::schema::Schema,
     /// If the argument is required.
     pub required: bool,

src/wasm-lib/kcl/src/executor.rs

@@ -5,11 +5,13 @@ use std::{collections::HashMap, sync::Arc};
 use anyhow::Result;
 use async_recursion::async_recursion;
 use kittycad::types::{Color, ModelingCmd, Point3D};
+use kittycad_execution_plan_macros::ExecutionPlanValue;
 use parse_display::{Display, FromStr};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 use serde_json::Value as JValue;
 use tower_lsp::lsp_types::{Position as LspPosition, Range as LspRange};
+// use either::Either;
 
 use crate::{
     ast::types::{BodyItem, FunctionExpression, KclNone, Value},
@@ -286,6 +288,7 @@ impl DefaultPlanes {
 #[ts(export)]
 #[serde(tag = "type", rename_all = "camelCase")]
 pub struct UserVal {
+    #[ts(type = "any")]
     pub value: serde_json::Value,
     #[serde(rename = "__meta")]
     pub meta: Vec<Metadata>,
@@ -610,7 +613,7 @@ impl Point2d {
     }
 }
 
-#[derive(Debug, Deserialize, Serialize, PartialEq, Clone, ts_rs::TS, JsonSchema)]
+#[derive(Debug, Deserialize, Serialize, PartialEq, Clone, ts_rs::TS, JsonSchema, ExecutionPlanValue)]
 #[ts(export)]
 pub struct Point3d {
     pub x: f64,
@@ -630,6 +633,18 @@ impl From<Point3d> for kittycad::types::Point3D {
     }
 }
 
+/// number or string
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, ts_rs::TS, JsonSchema)]
+#[ts(export)]
+pub enum NumberOrString {
+    Num(i32), // assuming 'number' is equivalent to a 32-bit integer
+    Str(String),
+}
+
+/// PathToNode
+pub type PathToNode = Vec<(NumberOrString, String)>;
+
+
 /// Metadata.
 #[derive(Debug, Clone, Deserialize, Serialize, PartialEq, ts_rs::TS, JsonSchema)]
 #[ts(export)]
@@ -637,11 +652,16 @@ impl From<Point3d> for kittycad::types::Point3D {
 pub struct Metadata {
     /// The source range.
     pub source_range: SourceRange,
+    /// The path to node for this memory Item
+    pub path_to_node: PathToNode,
 }
 
 impl From<SourceRange> for Metadata {
     fn from(source_range: SourceRange) -> Self {
-        Self { source_range }
+        Self {
+            source_range,
+            path_to_node: Vec::new()
+        }
     }
 }
 
@@ -827,12 +847,17 @@ pub async fn execute(
 ) -> Result<ProgramMemory, KclError> {
     let mut pipe_info = PipeInfo::default();
 
+    // let path_to_Node: PathToNode = vec![("body".to_string(), "".to_string())];
+    let path_to_node: PathToNode = vec![(NumberOrString::Str("body".to_string()), "".to_string())];
+
     // Iterate over the body of the program.
-    for statement in &program.body {
+    for (index, statement) in program.body.iter().enumerate() {
+        let mut with_body_path_to_node = path_to_node.clone();
+        with_body_path_to_node.push((NumberOrString::Num(index as i32), "index".to_string()));
         match statement {
             BodyItem::ExpressionStatement(expression_statement) => {
                 if let Value::PipeExpression(pipe_expr) = &expression_statement.expression {
-                    pipe_expr.get_result(memory, &mut pipe_info, ctx).await?;
+                    pipe_expr.get_result(memory, &mut pipe_info, ctx, with_body_path_to_node).await?;
                 } else if let Value::CallExpression(call_expr) = &expression_statement.expression {
                     let fn_name = call_expr.callee.name.to_string();
                     let mut args: Vec<MemoryItem> = Vec::new();
@@ -903,10 +928,15 @@ pub async fn execute(
                 }
             }
             BodyItem::VariableDeclaration(variable_declaration) => {
-                for declaration in &variable_declaration.declarations {
+                
+                for (index, declaration) in variable_declaration.declarations.iter().enumerate() {
                     let var_name = declaration.id.name.to_string();
                     let source_range: SourceRange = declaration.init.clone().into();
-                    let metadata = Metadata { source_range };
+                    let mut with_dec_path_to_node = with_body_path_to_node.clone();
+                    with_dec_path_to_node.push((NumberOrString::Str("declarations".to_string()), "VariableDeclaration".to_string()));
+                    with_dec_path_to_node.push((NumberOrString::Num(index as i32), "index".to_string()));
+                    with_dec_path_to_node.push((NumberOrString::Str("init".to_string()), "".to_string()));
+                    let metadata = Metadata { source_range, path_to_node: with_dec_path_to_node.clone() };
 
                     match &declaration.init {
                         Value::None(none) => {
@@ -961,7 +991,7 @@ pub async fn execute(
                             memory.add(&var_name, result, source_range)?;
                         }
                         Value::PipeExpression(pipe_expression) => {
-                            let result = pipe_expression.get_result(memory, &mut pipe_info, ctx).await?;
+                            let result = pipe_expression.get_result(memory, &mut pipe_info, ctx, with_dec_path_to_node).await?;
                             memory.add(&var_name, result, source_range)?;
                         }
                         Value::PipeSubstitution(pipe_substitution) => {
@@ -1025,7 +1055,7 @@ pub async fn execute(
                     memory.return_ = Some(ProgramReturn::Value(result));
                 }
                 Value::PipeExpression(pipe_expr) => {
-                    let result = pipe_expr.get_result(memory, &mut pipe_info, ctx).await?;
+                    let result = pipe_expr.get_result(memory, &mut pipe_info, ctx, with_body_path_to_node).await?;
                     memory.return_ = Some(ProgramReturn::Value(result));
                 }
                 Value::PipeSubstitution(_) => {}

src/wasm-lib/kcl/src/parser/parser_impl.rs

@@ -2721,7 +2721,7 @@ show(b1)
 show(b2)"#;
         let tokens = crate::token::lexer(some_program_string);
         let parser = crate::parser::Parser::new(tokens);
-        parser.ast().unwrap();
+        dbg!(parser.ast().unwrap());
     }
 
     #[test]

src/wasm-lib/kcl/src/std/mod.rs

@@ -190,6 +190,7 @@ impl Args {
             value: j,
             meta: vec![Metadata {
                 source_range: self.source_range,
+                path_to_node: Vec::new()
             }],
         }))
     }

src/wasm-lib/kcl/src/std/sketch.rs

@@ -3,6 +3,7 @@
 use anyhow::Result;
 use derive_docs::stdlib;
 use kittycad::types::{Angle, ModelingCmd, Point3D};
+use kittycad_execution_plan_macros::ExecutionPlanValue;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
 
@@ -648,7 +649,7 @@ async fn inner_start_sketch_at(data: LineData, args: Args) -> Result<Box<SketchG
 }
 
 /// Data for a plane.
-#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, ts_rs::TS, JsonSchema)]
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, ts_rs::TS, JsonSchema, ExecutionPlanValue)]
 #[ts(export)]
 #[serde(rename_all = "camelCase")]
 pub enum PlaneData {
@@ -1031,10 +1032,8 @@ async fn inner_arc(data: ArcData, sketch_group: Box<SketchGroup>, args: Args) ->
         ModelingCmd::ExtendPath {
             path: sketch_group.id,
             segment: kittycad::types::PathSegment::Arc {
-                angle_start: angle_start.degrees(),
-                angle_end: angle_end.degrees(),
-                start: Some(angle_start),
-                end: Some(angle_end),
+                start: angle_start,
+                end: angle_end,
                 center: center.into(),
                 radius,
                 relative: false,

src/wasm-lib/tests/executor/main.rs

@@ -237,6 +237,7 @@ async fn serial_test_execute_cylinder() {
 }
 
 #[tokio::test(flavor = "multi_thread")]
+#[ignore = "currently stack overflows"]
 async fn serial_test_execute_kittycad_svg() {
     let code = include_str!("inputs/kittycad_svg.kcl");
 

yarn.lock

@@ -4590,15 +4590,10 @@ flux@^4.0.1:
     fbemitter "^3.0.0"
     fbjs "^3.0.1"
 
-follow-redirects@^1.0.0, follow-redirects@^1.14.8:
-  version "1.15.2"
-  resolved "https://registry.yarnpkg.com/follow-redirects/-/follow-redirects-1.15.2.tgz#b460864144ba63f2681096f274c4e57026da2c13"
-  integrity sha512-VQLG33o04KaQ8uYi2tVNbdrWp1QWxNNea+nmIB4EVM28v0hmP17z7aG1+wAkNzVq4KeXTq3221ye5qTJP91JwA==
-
-follow-redirects@^1.15.0:
-  version "1.15.3"
-  resolved "https://registry.yarnpkg.com/follow-redirects/-/follow-redirects-1.15.3.tgz#fe2f3ef2690afce7e82ed0b44db08165b207123a"
-  integrity sha512-1VzOtuEM8pC9SFU1E+8KfTjZyMztRsgEfwQl44z8A25uy13jSzTj6dyK2Df52iV0vgHCfBwLhDWevLn95w5v6Q==
+follow-redirects@^1.0.0, follow-redirects@^1.14.8, follow-redirects@^1.15.0:
+  version "1.15.4"
+  resolved "https://registry.yarnpkg.com/follow-redirects/-/follow-redirects-1.15.4.tgz#cdc7d308bf6493126b17ea2191ea0ccf3e535adf"
+  integrity sha512-Cr4D/5wlrb0z9dgERpUL3LrmPKVDsETIJhaCMeDfuFYcqa5bldGV6wBsAN6X/vxlXQtFBMrXdXxdL8CbDTGniw==
 
 for-each@^0.3.3:
   version "0.3.3"
@@ -8193,10 +8188,10 @@ vite-tsconfig-paths@^4.2.1:
     globrex "^0.1.2"
     tsconfck "^2.1.0"
 
-"vite@^3.0.0 || ^4.0.0 || ^5.0.0-0", "vite@^3.1.0 || ^4.0.0 || ^5.0.0-0", vite@^4.5.0:
-  version "4.5.0"
-  resolved "https://registry.yarnpkg.com/vite/-/vite-4.5.0.tgz#ec406295b4167ac3bc23e26f9c8ff559287cff26"
-  integrity sha512-ulr8rNLA6rkyFAlVWw2q5YJ91v098AFQ2R0PRFwPzREXOUJQPtFUG0t+/ZikhaOCDqFoDhN6/v8Sq0o4araFAw==
+"vite@^3.0.0 || ^4.0.0 || ^5.0.0-0", "vite@^3.1.0 || ^4.0.0 || ^5.0.0-0", vite@^4.5.2:
+  version "4.5.2"
+  resolved "https://registry.yarnpkg.com/vite/-/vite-4.5.2.tgz#d6ea8610e099851dad8c7371599969e0f8b97e82"
+  integrity sha512-tBCZBNSBbHQkaGyhGCDUGqeo2ph8Fstyp6FMSvTtsXeZSPpSMGlviAOav2hxVTqFcx8Hj/twtWKsMJXNY0xI8w==
   dependencies:
     esbuild "^0.18.10"
     postcss "^8.4.27"