Typescript 4.4 leaks watchers

[RichyHBM]

Bug Report

🔎 Search Terms

• leak
• watcher

🕗 Version & Regression Information

4.4

• This changed between versions 4.3.5 and 4.4.2
• This is still the behavior in next version 4.5.0-dev.20210830

⏯ Playground Link

https://github.com/sveltejs/template

🙁 Actual behavior

Builds hang indefinitely

🙂 Expected behavior

Build should complete within a timely manner.

---

This is a bug to relay the information @michael42 found in the rollup bug rollup/plugins#983

Running my (hanging) build (with an empty file to bundle) using why-is-node-running produces this output:

There are 13 handle(s) keeping the process running

# Timeout
node:internal/async_hooks:205                                                                    
node:internal/async_hooks:495                                                                    
node:internal/timers:162                                                                         
node:internal/timers:196                                                                         
/project/rollup.config.js:16                                   - dir: "build",
node:internal/modules/cjs/loader:1101                                                            
/project/node_modules/rollup/dist/shared/loadConfigFile.js:540 - module._compile(bundledCode, requiredFileName);
node:internal/modules/cjs/loader:981                                                             

# TTYWRAP
node:internal/async_hooks:205                                                       
node:internal/bootstrap/switches/is_main_thread:47                                  
node:internal/bootstrap/switches/is_main_thread:135                                 
node:internal/console/constructor:216                                               
node:internal/console/constructor:333                                               
node:internal/console/constructor:368                                               
/project/node_modules/rollup/dist/bin/rollup:1506 - loadConfigFile_js.stderr(loadConfigFile_js.cyan(`\n${loadConfigFile_js.bold(inputFiles)} → ${loadConfigFile_js.bold(files.join(', '))}...`));
/project/node_modules/rollup/dist/bin/rollup:1692 - await build(inputOptions, warnings, command.silent);

# STATWATCHER
node:internal/async_hooks:205                                                               
node:internal/fs/watchers:105                                                               
/project/node_modules/typescript/lib/typescript.js:7670   - _fs.watchFile(fileName, { persistent: true, interval: pollingInterval }, fileChanged);
/project/node_modules/typescript/lib/typescript.js:6924   - watcher: watchFile(fileName, function (fileName, eventKind) { return ts.forEach(callbacksCache.get(path), function (cb) { return cb(fileName, eventKind); }); }, pollingInterval, options),
/project/node_modules/typescript/lib/typescript.js:7247   - return pollingWatchFile(fileName, callback, PollingInterval.Low, /*options*/ undefined);
/project/node_modules/typescript/lib/typescript.js:110912 - watchFile: function (file, callback, pollingInterval, options) { return host.watchFile(file, callback, pollingInterval, options); },
/project/node_modules/typescript/lib/typescript.js:110938 - factory[key].call(/*thisArgs*/ undefined, file, cb, flags, options, detailInfo1, detailInfo2) :
/project/node_modules/typescript/lib/typescript.js:118559 - return watchFile(file, function (fileName, eventKind) { return callback(fileName, eventKind, path); }, pollingInterval, options, watchType);

# STATWATCHER
node:internal/async_hooks:205                                                               
node:internal/fs/watchers:105                                                               
/project/node_modules/typescript/lib/typescript.js:7670   - _fs.watchFile(fileName, { persistent: true, interval: pollingInterval }, fileChanged);
/project/node_modules/typescript/lib/typescript.js:6924   - watcher: watchFile(fileName, function (fileName, eventKind) { return ts.forEach(callbacksCache.get(path), function (cb) { return cb(fileName, eventKind); }); }, pollingInterval, options),
/project/node_modules/typescript/lib/typescript.js:7247   - return pollingWatchFile(fileName, callback, PollingInterval.Low, /*options*/ undefined);
/project/node_modules/typescript/lib/typescript.js:110912 - watchFile: function (file, callback, pollingInterval, options) { return host.watchFile(file, callback, pollingInterval, options); },
/project/node_modules/typescript/lib/typescript.js:110938 - factory[key].call(/*thisArgs*/ undefined, file, cb, flags, options, detailInfo1, detailInfo2) :
/project/node_modules/typescript/lib/typescript.js:118559 - return watchFile(file, function (fileName, eventKind) { return callback(fileName, eventKind, path); }, pollingInterval, options, watchType);

[... 9 more # STATWATCHER] 

It seems to me that TypeScript is keeping open a few watchers... I added a few console.log at typescript.js:7670 and it seems that Typescript creates a lot of watchers and does not unregister all of them (383/394 in my case, which is consistent with the 11 STATWATCHER in the output). Analyzing the output, it seems that the watchers for the package.jsons of the @types packages are not properly closed (package.jsons are only loaded from @types packages in my output and all 11 of them are not closed):

Set(11) {
  '/project/common/node_modules/@types/pouchdb-core/package.json',
  '/project/common/node_modules/@types/pouchdb-find/package.json',
  '/project/node_modules/@types/pouchdb-core/package.json',
  '/project/node_modules/@types/pouchdb-find/package.json',
  '/project/server/node_modules/@types/benchmark/package.json',
  '/project/server/node_modules/@types/debug/package.json',
  '/project/server/node_modules/@types/express-serve-static-core/package.json',
  '/project/server/node_modules/@types/node/package.json',
  '/project/server/node_modules/@types/pouchdb-core/package.json',
  '/project/server/node_modules/@types/pouchdb-find/package.json',
  '/project/server/node_modules/@types/serve-static/package.json',
}

[andrewbranch]

Possibly related to #44935