Simplify and consolidate LSP watcher registrations #1733

andrewbranch · 2025-09-19T21:41:32Z

In a large internal monorepo, this cut the number of individual globs we ask the LSP client to watch from 7667 (duplicated and narrower) globs to 7 (deduped and broader) globs, and cut the time it took to compute and register those globs by 80%. This is the basis for two follow-up fixes/improvements:

Change our registered globs to be extensionless in order to work around API: file watching doesn't report file deletions caused by directory deletion vscode#109754
Clear the file cache manually when a large number of files change in a short period of time, as some events are dropped by VS Code (LSP: changes to files not open in editor are sometimes not picked up #1646)

I want to get reviews on this first, as those fixes will build on this simplification.

andrewbranch · 2025-09-30T19:47:36Z

internal/project/projectcollectionbuilder.go

 				// !!! what about declaration files in node_modules? wouldn't it be better to
 				//     check project inclusion if the project is already loaded?
-				if !config.MatchesFileName(fileName) {
+				if _, ok := config.FileNamesByPath()[path]; !ok {


This was a drive-by fix, but MatchesFileName is a more expensive function that speculates about files that may not exist; the usage here was for a file that already exists and is either properly included by the config or not.

andrewbranch · 2025-09-30T19:49:37Z

internal/project/session_test.go

 			assert.Check(t, lsAfter.GetProgram() != programBefore)
 		})

+		t.Run("change program file not in tsconfig root files", func(t *testing.T) {


This test case exercises logic that was missing from the pre-snapshot LSP port.

andrewbranch · 2025-09-30T19:56:46Z

internal/project/watch.go

The removals in this file represent two strategy changes:

Since we rely on the LSP client to handle the watchers at the system level, remove our logic for avoiding installing watchers too close to the file system root. VS Code installs a watcher at the workspace level no matter that directory’s location, so we have nothing to gain by not using it. Any decision to refuse installing a watcher at a given location belongs to the client; they can simply return an error when we request to watch that location.

Prefer watching the workspace directory over anything else. If a file is in the workspace, don't register any additional watcher.

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andrewbranch · 2025-09-30T20:00:50Z

internal/tsoptions/parsedcommandline.go

 }

-// Porting reference: ProjectService.isMatchedByConfig
-func (p *ParsedCommandLine) MatchesFileName(fileName string) bool {


MatchesFileName was no longer being used except for the incorrect usage I pointed out above. When I initially implemented it for file watching, it was a bad performance bottleneck. PossiblyMatchesFileName is less precise but faster. It may be worth revisiting this if we invest into perf improvements of our include/exclude globbing (#1483)

jakebailey · 2025-09-30T20:54:37Z

internal/lsp/server.go

 	}

+	cwd := s.cwd
+	if s.initializeParams.Capabilities != nil &&


Boy do I want to add protobuf-style safe accessors for capabilities

jakebailey · 2025-10-01T21:29:45Z

https://gist.github.com/jakebailey/84d5310acdb3397056009e0bbf998070 The big list of paths is me logging all of the files from createResolutionLookupGlobMapper (sorted).

andrewbranch · 2025-10-06T20:38:37Z

@jakebailey could you try the latest? I walked back some of the deletions while keeping it still much simpler than before.

jakebailey · 2025-10-06T20:47:59Z

Seems better:

[13:46:59.337] Added new watch: root files for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 9.0
[13:46:59.337] 	/home/jabaile/work/TypeScript/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.337] 
[13:46:59.344] Added new watch: non-root program files for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 10.1
[13:46:59.344] 	/home/jabaile/work/TypeScript-go/built/local/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.344] 
[13:46:59.352] Added new watch: failed lookups for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 12.0
[13:46:59.352] 	/home/jabaile/work/TypeScript/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.352] 
[13:46:59.353] Added new watch: failed lookups for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 12.1
[13:46:59.353] 	/node_modules/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.353] 
[13:46:59.354] Added new watch: failed lookups for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 12.2
[13:46:59.355] 	/home/jabaile/work/node_modules/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.355] 
[13:46:59.356] Added new watch: failed lookups for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 12.3
[13:46:59.356] 	/home/node_modules/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.356] 
[13:46:59.357] Added new watch: failed lookups for /home/jabaile/work/TypeScript/src/compiler/tsconfig.json watcher 12.4
[13:46:59.357] 	/home/jabaile/node_modules/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[13:46:59.357] 
[13:46:59.357] Updated watches in 62.427381ms

Those are all definitely safe paths to watch.

jakebailey · 2025-10-06T20:48:38Z

Though, the workspace ones seem potentially redundant? (Depending on how the editor does things)

andrewbranch · 2025-10-06T20:56:48Z

It's not reflected in the logs here, but they appear duplicated because the failed lookups one is a create-only watcher, while the root files for the tsconfig one is a create/change/delete watcher. In theory, one of those could be independently removed if you start opening and closing other projects. We could make a special rule that says “any watcher on the workspace directory is always create/change/delete” but I’m not sure how worthwhile that is.

jakebailey · 2025-10-06T21:04:21Z

This is a weird one; I opened DT tools to packages/mergebot/src/pr-info.ts, then opened packages/publisher/src/lib/secrets.ts and got this new watch:

[14:01:36.107] Added new watch: failed lookups for /home/jabaile/work/DefinitelyTyped-tools/packages/publisher/tsconfig.json watcher 37.5
[14:01:36.107] 	/home/jabail/typescript/**/*.{js,jsx,mjs,cjs,ts,tsx,mts,cts,json}
[14:01:36.107] 
[14:01:36.108] Updated watches in 13.083169ms

But, that path doesn't exist and isn't mentioned anywhere else in the logs. This is a failed lookup so maybe there's a bad import somewhere that's not resolving, but I can't seem to find it.

jakebailey · 2025-10-06T21:12:27Z

Just realized, /home/jabail/typescript/ doesn't make sense because my username is jabaile. So definitely some string weirdness.

andrewbranch · 2025-10-06T21:22:56Z

It’s happening to me too, but it’s not in a bug in the watcher code; that’s an actual module resolution lookup 😮

…ode_modules

andrewbranch · 2025-10-06T21:56:45Z

It looks like the same bug exists in Strada. I prevented the bogus path lookup for now but I’m not sure if a different strategy should be implemented to find the proper peer dep lookup location, or if it doesn’t matter for monorepo packages like this. (@sheetalkamat you might want to look at the last commit)

jakebailey

I can't find any weird issues when I try this out and read the logs. Worth a shot!

jakebailey · 2025-10-06T22:52:24Z

I'll note that in the TS repo, if I delete node_modules, nothing changes; there's no event for this. But, that happens on main, too. Which I believe is that known VS Code issue.

andrewbranch · 2025-10-06T23:00:07Z

Yeah, that’s microsoft/vscode#109754, and will be handled in a follow-up PR to remove the extensions from our glob patterns.

andrewbranch · 2025-10-06T23:08:11Z

I merged main because license/cla was MIA, but I have not super high hopes that a new commit is going to unstick it...

jakebailey · 2025-10-06T23:09:07Z

A close reopen usually fixes it for me.

andrewbranch added 7 commits September 18, 2025 13:47

Minimize number of watch globs

99939d9

Log watch update time

eebeee8

Update root files watch too

4acad53

Tweak workspace watching rules

31e58bf

Add failing test for watching file outside of tsconfig root files

4f1094d

Add non-root program file watch, fix watcher removal

20ab1fd

Lint

0761a15

andrewbranch mentioned this pull request Sep 22, 2025

LSP: changes to files not open in editor are sometimes not picked up #1646

Open

andrewbranch added 7 commits September 22, 2025 15:16

Fix GetCommonParents

a0af908

Use GetCommonParents instead of node_modules strategy

9369c83

Remove checks to see if locations are watchable

2c05e61

Fix bugs, make tests pass

be4e57f

Forgot to use PossiblyMatchesFileName and delete watcher parsed globs

fc75e42

Bad Copilot

da0795f

Fix test for updated signature

d8dab73

andrewbranch changed the title ~~Reduce number of LSP file watcher registrations~~ Simplify and consolidate LSP watcher registrations Sep 30, 2025

andrewbranch marked this pull request as ready for review September 30, 2025 19:45

Copilot AI review requested due to automatic review settings September 30, 2025 19:45

andrewbranch commented Sep 30, 2025

View reviewed changes

Revert formatting change

cb61cb8

andrewbranch commented Sep 30, 2025

View reviewed changes

Copilot AI reviewed Sep 30, 2025

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andrewbranch commented Sep 30, 2025

View reviewed changes

Fix race

8755d8f

andrewbranch force-pushed the simplify-watch branch from eb8d310 to 8755d8f Compare September 30, 2025 20:10

Fix build

a32714e

andrewbranch requested review from jakebailey and sheetalkamat September 30, 2025 20:35

jakebailey reviewed Sep 30, 2025

View reviewed changes

andrewbranch mentioned this pull request Oct 1, 2025

Port source map position mapping + go to definition source mapping #1767

Merged

Bring back some minimal strategies to avoid super broad globs

af91353

Drive-by fix peer dependency lookup when realpath of package not in n…

95ea6b1

…ode_modules

andrewbranch requested a review from jakebailey October 6, 2025 22:00

jakebailey approved these changes Oct 6, 2025

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andrewbranch enabled auto-merge October 6, 2025 23:00

Merge branch 'main' into simplify-watch

89586c1

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andrewbranch enabled auto-merge October 6, 2025 23:09

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andrewbranch added this pull request to the merge queue Oct 7, 2025

Simplify and consolidate LSP watcher registrations #1733

Simplify and consolidate LSP watcher registrations #1733

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