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https://github.com/webpack/watchpack

Wrapper library for directory and file watching.
https://github.com/webpack/watchpack

Last synced: about 1 month ago
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Wrapper library for directory and file watching.

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# watchpack



Wrapper library for directory and file watching.



[![Test](https://github.com/webpack/watchpack/actions/workflows/test.yml/badge.svg)](https://github.com/webpack/watchpack/actions/workflows/test.yml)

[![Codecov](https://codecov.io/gh/webpack/watchpack/graph/badge.svg?token=8xk2OrrxWm)](https://codecov.io/gh/webpack/watchpack)

[![Downloads](https://img.shields.io/npm/dm/watchpack.svg)](https://www.npmjs.com/package/watchpack)



## Concept



watchpack high level API doesn't map directly to watchers. Instead a three level architecture ensures that for each directory only a single watcher exists.



- The high level API requests `DirectoryWatchers` from a `WatcherManager`, which ensures that only a single `DirectoryWatcher` per directory is created.

- A user-faced `Watcher` can be obtained from a `DirectoryWatcher` and provides a filtered view on the `DirectoryWatcher`.

- Reference-counting is used on the `DirectoryWatcher` and `Watcher` to decide when to close them.

- The real watchers are created by the `DirectoryWatcher`.

- Files are never watched directly. This should keep the watcher count low.

- Watching can be started in the past. This way watching can start after file reading.

- Symlinks are not followed, instead the symlink is watched.



## API



```javascript

var Watchpack = require("watchpack");



var wp = new Watchpack({

	// options:

	aggregateTimeout: 1000,

	// fire "aggregated" event when after a change for 1000ms no additional change occurred

	// aggregated defaults to undefined, which doesn't fire an "aggregated" event



	poll: true,

	// poll: true - use polling with the default interval

	// poll: 10000 - use polling with an interval of 10s

	// poll defaults to undefined, which prefer native watching methods

	// Note: enable polling when watching on a network path

	// When WATCHPACK_POLLING environment variable is set it will override this option



	followSymlinks: true,

	// true: follows symlinks and watches symlinks and real files

	//   (This makes sense when symlinks has not been resolved yet, comes with a performance hit)

	// false (default): watches only specified item they may be real files or symlinks

	//   (This makes sense when symlinks has already been resolved)



	ignored: "**/.git"

	// ignored: "string" - a glob pattern for files or folders that should not be watched

	// ignored: ["string", "string"] - multiple glob patterns that should be ignored

	// ignored: /regexp/ - a regular expression for files or folders that should not be watched

	// ignored: (entry) => boolean - an arbitrary function which must return truthy to ignore an entry

	// For all cases expect the arbitrary function the path will have path separator normalized to '/'.

	// All subdirectories are ignored too

});



// Watchpack.prototype.watch({

//   files: Iterable,

//   directories: Iterable,

//   missing: Iterable,

//   startTime?: number

// })

wp.watch({

	files: listOfFiles,

	directories: listOfDirectories,

	missing: listOfNotExistingItems,

	startTime: Date.now() - 10000

});

// starts watching these files and directories

// calling this again will override the files and directories

// files: can be files or directories, for files: content and existence changes are tracked

//        for directories: only existence and timestamp changes are tracked

// directories: only directories, directory content (and content of children, ...) and

//              existence changes are tracked.

//              assumed to exist, when directory is not found without further information a remove event is emitted

// missing: can be files or directories,

//          only existence changes are tracked

//          expected to not exist, no remove event is emitted when not found initially

// files and directories are assumed to exist, when they are not found without further information a remove event is emitted

// missing is assumed to not exist and no remove event is emitted



wp.on("change", function(filePath, mtime, explanation) {

	// filePath: the changed file

	// mtime: last modified time for the changed file

	// explanation: textual information how this change was detected

});



wp.on("remove", function(filePath, explanation) {

	// filePath: the removed file or directory

	// explanation: textual information how this change was detected

});



wp.on("aggregated", function(changes, removals) {

	// changes: a Set of all changed files

	// removals: a Set of all removed files

	// watchpack gives up ownership on these Sets.

});



// Watchpack.prototype.pause()

wp.pause();

// stops emitting events, but keeps watchers open

// next "watch" call can reuse the watchers

// The watcher will keep aggregating events

// which can be received with getAggregated()



// Watchpack.prototype.close()

wp.close();

// stops emitting events and closes all watchers



// Watchpack.prototype.getAggregated(): { changes: Set, removals: Set }

const { changes, removals } = wp.getAggregated();

// returns the current aggregated info and removes that from the watcher

// The next aggregated event won't include that info and will only emitted

// when futher changes happen

// Can also be used when paused.



// Watchpack.prototype.collectTimeInfoEntries(fileInfoEntries: Map, directoryInfoEntries: Map)

wp.collectTimeInfoEntries(fileInfoEntries, directoryInfoEntries);

// collects time info objects for all known files and directories

// this include info from files not directly watched

// key: absolute path, value: object with { safeTime, timestamp }

// safeTime: a point in time at which it is safe to say all changes happened before that

// timestamp: only for files, the mtime timestamp of the file



// Watchpack.prototype.getTimeInfoEntries()

var fileTimes = wp.getTimeInfoEntries();

// returns a Map with all known time info objects for files and directories

// similar to collectTimeInfoEntries but returns a single map with all entries



// (deprecated)

// Watchpack.prototype.getTimes()

var fileTimes = wp.getTimes();

// returns an object with all known change times for files

// this include timestamps from files not directly watched

// key: absolute path, value: timestamp as number

```