Allow deletion of only item in AST (#6335)

* Update test to check for deletion of only operation

* Allow updateEditorWithAstAndWriteToFile to clear AST

* Update src/lang/codeManager.ts

Co-authored-by: Jonathan Tran <jonnytran@gmail.com>

* Weave `isDeleting` through to `deleteSelectionPromise`

* fmt

---------

Co-authored-by: Jonathan Tran <jonnytran@gmail.com>
Co-authored-by: Pierre Jacquier <pierrejacquier39@gmail.com>

src/lang/codeManager.ts

@@ -165,13 +165,16 @@ export default class CodeManager {
     }
   }
 
-  async updateEditorWithAstAndWriteToFile(ast: Program) {
+  async updateEditorWithAstAndWriteToFile(
+    ast: Program,
+    options?: Partial<{ isDeleting: boolean }>
+  ) {
     // We clear the AST when it cannot be parsed. If we are trying to write an
     // empty AST, it's probably because of an earlier error. That's a bad state
     // to be in, and it's not going to be pretty, but at the least, let's not
-    // permanently delete the user's code. If you want to clear the scene, call
-    // updateCodeStateEditor directly.
-    if (ast.body.length === 0) return
+    // permanently delete the user's code accidentally.
+    // if you want to clear the scene, pass in the `isDeleting` option.
+    if (ast.body.length === 0 && !options?.isDeleting) return
     const newCode = recast(ast)
     if (err(newCode)) return
     // Test to see if we can parse the recast code, and never update the editor with bad code.