Content mappers: let openProject watch a directory or glob, so a file added later reloads the mapper #65348

🔍 Search Terms

content mapper, contentMappers, openProject, watchedFiles, watch glob, watch directory, file added later, stale mapped output

✅ Viability Checklist

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
• This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

⭐ Suggestion

Let a content mapper ask for a reload when the set of files matching a directory or glob changes, for example a watchedGlobs / watchedDirectories field in the openProject result.

Today openProject can only list watchedFiles, and the mapper is reopened only when one of those paths changes. A mapper whose output depends on every file matching a pattern in its own config (for example files: ["./tailordb/*.ts"]) cannot list a file that does not exist yet, because the name is unknown. After a matching file is added, the mapped output stays stale until the project is reopened.

📃 Motivating Example

Version: typescript@7.1.0-beta (native), macOS arm64. Reproduced with tsc --watch --runExternalCode and in VS Code.

Setup: a mapper whose output depends on the files matching ./tailordb/*.ts. src/use.ts references a table defined only in a new file tailordb/invoice.ts, which is created after the first check.

In VS Code (TypeScript Native Preview 1.0.1 with typescript@7.1.0-beta selected through js/ts.tsdk.path, js/ts.contentMappers.enabled at its default), driven by a probe extension that keeps src/use.ts as the active editor and reads its diagnostics 40 s after each step:

A file that appears while the editor is running (a git checkout, a generator) leaves the mapped output stale until the server is restarted. tsc --watch did not reload it either.

💻 Use Cases

1. A mapper that derives output from a config file and the files that config selects (schema definitions, route files, and so on).
2. Today the mapper has no way to learn about a file that did not exist at openProject time, because the protocol accepts only exact file paths.
3. The only workaround is restarting the TypeScript server (editor) or the tsc --watch process after adding a file.