watchpack

Wrapper library for directory and file watching.

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

1var Watchpack = require("watchpack");
2
3var wp = new Watchpack({
4	// options:
5	aggregateTimeout: 1000,
6	// fire "aggregated" event when after a change for 1000ms no additional change occurred
7	// aggregated defaults to undefined, which doesn't fire an "aggregated" event
8
9	poll: true,
10	// poll: true - use polling with the default interval
11	// poll: 10000 - use polling with an interval of 10s
12	// poll defaults to undefined, which prefer native watching methods
13	// Note: enable polling when watching on a network path
14	// When WATCHPACK_POLLING environment variable is set it will override this option
15
16	followSymlinks: true,
17	// true: follows symlinks and watches symlinks and real files
18	//   (This makes sense when symlinks has not been resolved yet, comes with a performance hit)
19	// false (default): watches only specified item they may be real files or symlinks
20	//   (This makes sense when symlinks has already been resolved)
21
22	ignored: "**/.git"
23	// ignored: "string" - a glob pattern for files or folders that should not be watched
24	// ignored: ["string", "string"] - multiple glob patterns that should be ignored
25	// ignored: /regexp/ - a regular expression for files or folders that should not be watched
26	// ignored: (entry) => boolean - an arbitrary function which must return truthy to ignore an entry
27	// For all cases expect the arbitrary function the path will have path separator normalized to '/'.
28	// All subdirectories are ignored too
29});
30
31// Watchpack.prototype.watch({
32//   files: Iterable<string>,
33//   directories: Iterable<string>,
34//   missing: Iterable<string>,
35//   startTime?: number
36// })
37wp.watch({
38	files: listOfFiles,
39	directories: listOfDirectories,
40	missing: listOfNotExistingItems,
41	startTime: Date.now() - 10000
42});
43// starts watching these files and directories
44// calling this again will override the files and directories
45// files: can be files or directories, for files: content and existence changes are tracked
46//        for directories: only existence and timestamp changes are tracked
47// directories: only directories, directory content (and content of children, ...) and
48//              existence changes are tracked.
49//              assumed to exist, when directory is not found without further information a remove event is emitted
50// missing: can be files or directorees,
51//          only existence changes are tracked
52//          expected to not exist, no remove event is emitted when not found initially
53// files and directories are assumed to exist, when they are not found without further information a remove event is emitted
54// missing is assumed to not exist and no remove event is emitted
55
56wp.on("change", function(filePath, mtime, explanation) {
57	// filePath: the changed file
58	// mtime: last modified time for the changed file
59	// explanation: textual information how this change was detected
60});
61
62wp.on("remove", function(filePath, explanation) {
63	// filePath: the removed file or directory
64	// explanation: textual information how this change was detected
65});
66
67wp.on("aggregated", function(changes, removals) {
68	// changes: a Set of all changed files
69	// removals: a Set of all removed files
70	// watchpack gives up ownership on these Sets.
71});
72
73// Watchpack.prototype.pause()
74wp.pause();
75// stops emitting events, but keeps watchers open
76// next "watch" call can reuse the watchers
77// The watcher will keep aggregating events
78// which can be received with getAggregated()
79
80// Watchpack.prototype.close()
81wp.close();
82// stops emitting events and closes all watchers
83
84// Watchpack.prototype.getAggregated(): { changes: Set<string>, removals: Set<string> }
85const { changes, removals } = wp.getAggregated();
86// returns the current aggregated info and removes that from the watcher
87// The next aggregated event won't include that info and will only emitted
88// when futher changes happen
89// Can also be used when paused.
90
91// Watchpack.prototype.collectTimeInfoEntries(fileInfoEntries: Map<string, Entry>, directoryInfoEntries: Map<string, Entry>)
92wp.collectTimeInfoEntries(fileInfoEntries, directoryInfoEntries);
93// collects time info objects for all known files and directories
94// this include info from files not directly watched
95// key: absolute path, value: object with { safeTime, timestamp }
96// safeTime: a point in time at which it is safe to say all changes happened before that
97// timestamp: only for files, the mtime timestamp of the file
98
99// Watchpack.prototype.getTimeInfoEntries()
100var fileTimes = wp.getTimeInfoEntries();
101// returns a Map with all known time info objects for files and directories
102// similar to collectTimeInfoEntries but returns a single map with all entries
103
104// (deprecated)
105// Watchpack.prototype.getTimes()
106var fileTimes = wp.getTimes();
107// returns an object with all known change times for files
108// this include timestamps from files not directly watched
109// key: absolute path, value: timestamp as number