TS/JS file watchers watch too many files

[dummdidumm]

Describe the bug
The watcher in extension.ts and the fallbackwatcher in FallbackWatcher.ts both watch too many files. They ignore node_modules, but they do not ignore build output directories. This means for example for Sapper that any changes in __sapper__ are watched and the TS plugin adds them to the list of known files, which is wrong.

To Reproduce
Start a Sapper project, change files and force rebuilds, see the number of files increase over time.

Expected behavior
Build directories are ignored

This could be done on a best-effor basis by

• always ignoring __sapper__ and .svelte (SvelteKit)
• try to read a .gitignore file in the root of the opened workspace and ignore file changes in all those listed paths

I'm not sure we can completely transform this into a glob though, because the glob DSL is very limited. We might need to watch all files either way but filter out the events that come from the watcher based on the .gitignore.

[jasonlyu123]

Found that tsserver has a size limit for files. It would check the file sizes of the "project" loaded in. If the sizes exceed the 20MB limit. it would disable some features.

https://github.com/microsoft/TypeScript/blob/3c8e45b304b8572094c5d7fbb9cd768dbf6417c0/src/server/editorServices.ts#L1955
https://github.com/microsoft/TypeScript/blob/3c8e45b304b8572094c5d7fbb9cd768dbf6417c0/src/server/project.ts#L397

From my understanding, It seems like the disabled project would only load the files that are opened in the client. The files in the include field of tsconfig.json would not be used. I have a brief experiment with adopting the check, and it looks promising. Even if I configured to load all js files in the node_modules. The editor would still be responsive.

[dummdidumm]

Current state

• we no longer add files that are not part of the project include to the snapshot managers
• we now have this file size checker in place

What's left is to actually make the watcher watch less files, which I'm still not sure how to actually solve this.