When watching failed lookups, watch packageDir if its a symlink otherwise the path we use to watch

[sheetalkamat]

In mono repo scenarios the packages are linked using symlink.
So when trying to resolve package1 from package2 in the test we look for locations like: /home/src/projects/project/node_modules/package1/dist/index.d.ts

As a result when package1 fails to resolve, we want to watch if this path will exists.
Before this PR, we would be watching /home/src/projects/project/node_modules as its a node_modules folder and we dont want to be watching too many packages or folders. This results in issues because /home/src/projects/project/node_modules/package1 is a symlink and any changes to the target are not percolated to the watcher we create. So without this PR we would not see the changes and miss the package build and report errors about package1 not found and never be able to resolve that unless offcourse if you start fresh by restarting tsserver

Now when we calculate dir to watch, we also find the packageDir if this happens to be symlink, we will watch it otherwise we will watch the node_modules like we use to watch before.

Other change needed for this to work on linux was that when we are watching this symlink dir, we need to ensure we are watching the target recursively as that is the expectation for native watchers that support symlink watching.

We already had test case which didnt update the diagnostics on tsserver when paths was not used and with my other prototype changes to treat file create and delete as change and retain things more, it becomes more evident and those tests just start to fail. So this is cruicial fix for that change to go in as well

Fixes #55450

[jakebailey]

For these new watchers, my impression is that they are attempting to watch the future linking or changing of /user/username/projects/myproject/packages/B, right? Does the case matter here?

[sheetalkamat]

Casing is handled. Its not target we are watching but symlink so this is something we lookedup as part of failed lookup and we are watching that.

[openscript]

Thank you very much for your work on this! Highly appreciated 🎉

[r0ssIV]

@sheetalkamat could you update when this fix will be released in typescript?

[sheetalkamat]

This is already in 5.5 beta

[r0ssIV]

@sheetalkamat So this fix is already in prod?
Just switched to TS 5.5.3

Quick question: does it work only with .ts files imported from symlinked folder, or any .js files (for example from node_modules/@libraryname/{some_symlinked_folder}/dist/some_compiled_lib.js ?

Still having the issue with VSCode. One of my node_modules packages - node_modules/@libraryname/package is a symbolic link to another folder. If files are changed in that folder, should it detect changes?

P.S.: checked and it still does not, I need to call restart TS server in VSCode

[sheetalkamat]

This is in 5.5
If you are running into issues, pls file issue with logs and way to repro.