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watch: Debounce all files updates into a single event. #51988

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watch: Debounce all files updates into a single event. #51988

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768da12
watch: allow listening for grouped changes
matthieusieben Mar 6, 2024
906f7c8
Update lib/internal/watch_mode/files_watcher.js
matthieusieben Mar 11, 2024
e2ce54a
fix: import clearTimeout
matthieusieben Mar 11, 2024
ada7280
comment on creation of `owners` argument to FilesWatcher's changed event
matthieusieben Mar 11, 2024
f2e2232
Merge branch 'main' into patch-4
matthieusieben Mar 19, 2024
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27 changes: 19 additions & 8 deletions lib/internal/watch_mode/files_watcher.js
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Original file line number Diff line number Diff line change
Expand Up @@ -17,17 +17,18 @@ const { addAbortListener } = require('internal/events/abort_listener');
const { watch } = require('fs');
const { fileURLToPath } = require('internal/url');
const { resolve, dirname } = require('path');
const { setTimeout } = require('timers');
const { setTimeout, clearTimeout } = require('timers');

const supportsRecursiveWatching = process.platform === 'win32' ||
process.platform === 'darwin';

class FilesWatcher extends EventEmitter {
#watchers = new SafeMap();
#filteredFiles = new SafeSet();
#debouncing = new SafeSet();
#depencencyOwners = new SafeMap();
#ownerDependencies = new SafeMap();
#debounceOwners = new SafeSet();
#debounceTimer;
#debounce;
#mode;
#signal;
Expand Down Expand Up @@ -75,17 +76,27 @@ class FilesWatcher extends EventEmitter {
}

#onChange(trigger) {
if (this.#debouncing.has(trigger)) {
return;
}
if (this.#mode === 'filter' && !this.#filteredFiles.has(trigger)) {
return;
}
this.#debouncing.add(trigger);

const owners = this.#depencencyOwners.get(trigger);
setTimeout(() => {
this.#debouncing.delete(trigger);
if (owners) {
for (const owner of owners) {
this.#debounceOwners.add(owner);
}
}

clearTimeout(this.#debounceTimer);
this.#debounceTimer = setTimeout(() => {
this.#debounceTimer = null;
// In order to allow async processing of the 'changed' event, let's
// make sure the Set emitted is a new instance. We could emit using a copy
// of #debounceOwners, then clear #debounceOwners, but that would be
// slower than just replacing #debounceOwners with an empty Set.
const owners = this.#debounceOwners;
this.emit('changed', { owners });
this.#debounceOwners = new SafeSet();
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Suggested change
this.#debounceOwners = new SafeSet();
this.#debounceOwners.clear();

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The reason I did that is to allow async processing of the owners by the listeners. I figured it would be more efficient to swap the Set rather than doing:

      const owners = new Set(this.#debounceOwners);
      this.emit('changed', { owners });
      this.#debounceOwners.clear();

What do you think ?

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If you think that async processing of the event is not something we should care about here, then I can just implement your change.

}, this.#debounce).unref();
}

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