A new module written by AFT stays 'Cannot find module' in TypeScript diagnostics: AFT writes send no Created watched-file event #1165

Problem

When AFT's own write (or patch) creates a new TypeScript module, a file that imports it continues to report Cannot find module from the TypeScript server. The module is on disk and tsc passes. The same file created by a different program resolves after a few seconds.

Steps to reproduce (aft 0.62.0 module, TypeScript 6.0.3 through typescript-language-server)

A package with tsconfig.json (moduleResolution: "Bundler", allowImportingTsExtensions), local node_modules/typescript, and lib/use.ts:

import { scan } from "../src/scanner2.ts"
export const value: number = scan(1)
export const control: number = "positive control"

The control line is a positive control: it must always report an error.

1. aft_inspect with scope: ["lib/use.ts"]: Cannot find module '../src/scanner2.ts' and the control error. This is correct, because the module is missing.
2. Create src/scanner2.ts with AFT write:

   export function scan(n: number): number { return n + 1 }

3. aft_inspect again, immediately and again after 10 s: both times Cannot find module '../src/scanner2.ts' and the control error. Incorrect.

Control: point the import at ../src/scanner3.ts (an AFT edit), then create src/scanner3.ts from a shell instead of AFT. After 8 s, aft_inspect shows only the control error. The import resolves.

I ran each arm in two packages in the same project: one in a directory excluded through .git/info/exclude and one in a directory that git does not ignore. The results were the same in both, so ignore rules are not the cause.

Probable cause (main 666645637)

After an AFT write, lsp_post_write (crates/aft/src/context.rs:15521) sends didOpen/didChange for the written document. It sends workspace/didChangeWatchedFiles only for project configuration files (notify_watched_config_files, context.rs:15345-15362, filtered by is_config_file_path_with_custom). So the server gets no Created event for a new source file. The TypeScript server keeps its cached failed module lookup for the importer, and opening the new file does not clear it.

For a file that another program creates, the project watcher forwards the change (lsp_forward_classified_watcher_file_events), and the import resolves. The watcher does not do this for the AFT-written file in my test. I did not find where that event is dropped.

Suggested change

When an AFT write or patch creates a file (or deletes one), send workspace/didChangeWatchedFiles with Created (or Deleted) to each server whose root contains the path and which registered watchers for it, as for files that the watcher sees. A move is a Deleted plus a Created.

Effect

Agents get false errors on files that import a module they just wrote, plus follow-on implicit-any errors. They can spend time on a type error that does not exist.