TypeScript slow project load times for large projects on MacOS

Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: v1.96.2
• OS Version: MacOS
• TypeScript: v5.7.2 (workspace version)
• Node.JS: v20.18.0

Steps to Reproduce:

1. Add the following to .vscode/settings.json

  "typescript.tsserver.log": "verbose",
  "files.watcherExclude": {
    "**/node_modules": true
  },

This causes:

2024-12-20 13:49:42.785 [info] <syntax> Falling back to legacy node.js based file watching because of user settings.

2. Open a TS source file belonging to a large TS project with many project references in VSCode running on MacOS. For example, our project references a total of 25k+ files (transitively through project references):

Info 57414[13:12:03.001] Project '.../web/src/pages/editor/tsconfig.json' (Configured)
Info 57414[13:12:03.001] 	Files (26167)

3. Notice that the tsserver logs are littered with the following log lines:

Info 57094[13:34:37.437] DirectoryWatcher:: Triggered with .../web/src/pages/editor :: WatchInfo: .../web/src/pages/editor 1 {"watchFile":2,"watchDirectory":2,"excludeDirectories":["/Users/mjames/work/canva/web/**/node_modules",".../web/**/target",".../web/**/bazel-bin",".../web/**/bazel-out",".../web/**/bazel-canva"]} Config: /Users/mjames/work/<redacted>/tsconfig.json WatchType: Wild card directory
Info 57095[13:34:37.437] Invoking sourceFileChange on .../web/src/pages/editor/editor_bootstrap_proto.ts:: 1
Info 57096[13:34:37.438] Scheduled: .../web/src/pages/editor/tsconfig.json
Info 57097[13:34:37.438] Scheduled: *ensureProjectForOpenFiles*
Info 57098[13:34:37.438] Invoking sourceFileChange on .../web/src/pages/<redacted>:: 1
Info 57099[13:34:37.438] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57100[13:34:37.438] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57101[13:34:37.438] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57102[13:34:37.438] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57103[13:34:37.438] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57104[13:34:37.438] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57105[13:34:37.438] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57106[13:34:37.442] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57107[13:34:37.442] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57108[13:34:37.442] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57109[13:34:37.442] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57110[13:34:37.442] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57111[13:34:37.443] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57112[13:34:37.443] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57113[13:34:37.443] Invoking sourceFileChange on .../web/src/pages/editor/editing/<redacted>:: 1
Info 57114[13:34:37.443] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57115[13:34:37.443] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57116[13:34:37.443] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57117[13:34:37.443] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57118[13:34:37.443] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57119[13:34:37.443] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57120[13:34:37.443] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier one
Info 57121[13:34:37.443] Scheduled: *ensureProjectForOpenFiles*, Cancelled earlier one
Info 57122[13:34:37.443] Invoking sourceFileChange on .../web/src/pages/editor/<redacted>:: 1
Info 57123[13:34:37.443] Scheduled: .../web/src/pages/editor/tsconfig.json, Cancelled earlier
...

The strange thing is that this is NOT a problem with .vscode-server running on Linux.

None of the 20k+ Invoking sourceFileChange on... log lines appear in the tsserver logs when running in our Linux based remote dev envs and the load time for this project is ~52s vs 3m45s!

Interestingly the problem also does NOT occur on MacOS when tsserver reuses VSCode's file watcher (i.e. the node_modules excludes aren't in the files.watcherExclude hash)

まず、レポート内の再現設定と tsserver の出力を使用して、macOS のレガシーなファイル監視動作を、再利用されている VS Code watcher および Linux のリモートログと比較します。参照されている VS Code の設定エントリポイントをたどり、25k ファイルのプロジェクトの読み込みを計測します。完了の条件は、繰り返される sourceFileChange アクティビティをなくし、macOS の読み込み時間を大幅に短縮することです。