add helper 'getNodePathFromSourceRange' and it's test

src/lang/getNodePathFromSourceRange.test.ts

@@ -0,0 +1,27 @@
+import { getNodePathFromSourceRange } from './abstractSyntaxTree'
+import { lexer } from './tokeniser'
+import { abstractSyntaxTree, getNodeFromPath } from './abstractSyntaxTree'
+
+describe('testing getNodePathFromSourceRange', () => {
+    it('test it gets the right path for a `lineTo` CallExpression within a SketchExpression', () => {
+        const code = `
+        const myVar = 5
+        sketch sk3 {
+            lineTo(1, 2)
+            path yo = lineTo(3, 4)
+            close()
+        }
+        `
+        const subStr = 'lineTo(3, 4)'
+        const lineToSubstringIndex = code.indexOf(subStr)
+        const sourceRange: [number, number] = [lineToSubstringIndex, lineToSubstringIndex + subStr.length]
+
+        const ast = abstractSyntaxTree(lexer(code))
+        const nodePath = getNodePathFromSourceRange(ast, sourceRange)
+        const node = getNodeFromPath(ast, nodePath)
+
+        expect([node.start, node.end]).toEqual(sourceRange)
+        expect(node.type).toBe('CallExpression')
+
+    })
+})