gulp-watch

Watch, that actually is an endless stream

npm install gulp-watch
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Watch, that actually is an endless stream

This is implementation of gulp.watch with endless stream approach. If gulp.watch is working for you - stick with it, otherwise you can try gulp-watch plugin.

Main reasons of gulp-watch existance is that it can easly (with a little help of gulp-plumber achieve per-file rebuilding on file change:

Awesome demonstration

Usage

var gulp = require('gulp'),
    watch = require('gulp-watch');

gulp.task('default', function () {
    gulp.src('scss/**/*.scss')
        .pipe(watch(function(files) {
            return files.pipe(sass())
                .pipe(gulp.dest('./dist/'));
        }));
});

Batching mode

This is close to bundled gulp.watch, but with some tweaks. First - files will be grouped by timeout of 200 and passed into stream inside callback (this will keep git checkout commands do rebuilding only once). Second - callbacks will never run parallel (unless you remove return), until one stream ends working.

var gulp = require('gulp'),
    watch = require('gulp-watch');

gulp.task('default', function () {
    gulp.src('scss/**/*.scss')
        .pipe(watch(function(files) {
            return files.pipe(sass())
                .pipe(gulp.dest('./dist/'));
        }));
});

To watch entire glob of files and directories you should use glob option. In this case gulp-watch will pipe files matching glob downstream, and begin watching them. Moreover, any newly created files that match glob will also be piped downstream, and be watched for changes.

var gulp = require('gulp'),
    watch = require('gulp-watch');

gulp.task('default', function () {
    watch({glob: 'scss/**/*.scss'}, function(files) {
        return files.pipe(sass())
            .pipe(gulp.dest('./dist/'));
    });
});

Continuous stream of events

This is usefull, when you want blazingly fast rebuilding per-file.

Be aware: end event is never happens in this mode, so plugins dependent on it will never print or do whatever they should do on end task.

// npm i gulp gulp-watch gulp-sass

var gulp = require('gulp'),
    watch = require('gulp-watch'),
    plumber = require('gulp-plumber'),
    sass = require('gulp-sass');

gulp.task('default', function () {
    gulp.src('scss/**', { read: false })
        .pipe(watch())
        .pipe(plumber()) // This will keeps pipes working after error event
        .pipe(sass())
        .pipe(gulp.dest('./dist/'));
});

Same as before - version with glob option:

gulp.task('default', function () {
    watch({ glob: 'sass/**/*.scss' })
        .pipe(plumber())
        .pipe(sass())
        .pipe(gulp.dest('./dist/'));
});

Trigger for mocha

Problem with gulp.watch is that will run your test suit on every changed file per once. To avoid this gulp-batch was written first, but after some time it became clear, that gulp.watch should be a plugin with event batching abilities.

var grep = require('gulp-grep-stream');
var mocha = require('gulp-mocha');
var plumber = require('gulp-plumber');

gulp.task('default', function() {
    gulp.src(['lib/**', 'test/**'], { read: false })
        .pipe(watch({ emit: 'all' }, function(files) {
            files
                .pipe(grep('*/test/*.js'))
                .pipe(mocha({ reporter: 'spec' }))
                .on('error', function() {
                    if (!/tests? failed/.test(err.stack)) {
                        console.log(err.stack);
                    }
                })
        }));
});

Filtering custom event

When you want to make actions only on specific event, you can use gulp-filter and event attribute, which is added to all files, that was added, changed or deleted (as gaze documentation says):

var filter = require('gulp-filter');

function isAdded(file) {
    return file.event === 'added';
}
gulp.task('default', function () {
    watch({glob: '**/*.js'})
        .pipe(filter(isAdded))
        .pipe(gulp.dest('newfiles'))
        .pipe(filter.restore())
        .pipe(gulp.dest('oldfiles'));
});

Notice: event property is not added to files, that was emitted by emitOnGlob and emit: 'all' options, only to files, that actually caused event.

API

watch([options, callback])

This function creates have two different modes, that are depends on have you provice callback function, or not. If you do - you get batched mode, if you not - you get stream.

Callback signature: function(events, [done])

  • events - is Stream of incoming events.
  • done - is callback for your function signal to batch, that you are done. This allows to run your callback as soon as previous end.

Options:

This object passed to gaze options directly, so see documentation there. For batched mode we are using gulp-batch, so options from there are available. And of course options for gulp.src used too. If you do not want content from watch, then add read: false to options object.

options.emit

Type: String Default: one

This options defines emit strategy:

  • one - emit only changed file
  • all - emit all watched files (and folders), when one changes

options.passThrough

Type: Boolean
Default: true

This options will pass vinyl objects, that was piped into watch to next Stream in pipeline.

options.glob

Type: String|Array
Default: undefined

If you want to detect new files, then you have to use this option. When gulp-watch gets files from gulp.src it looses the information about pattern of matching - therefore it can not detect new files, but with passed pattern in this option, gulp-watch will watch all files, that matched pattern and any new files, that was created after watch started and match glob pattern.

options.base

Type: String
Default: undefined

Use explicit base path for files from glob.

options.emitOnGlob

Type: Boolean
Default: true

If options.glob is used, gulp-watch, by default, will emit files when beginning to watch them -- much like gulp.src(). Otherwise, disable this option.

Example:

// gulp-watch will not emit like gulp.src(...)
watch({glob:'./src/**/*.md', emitOnGlob: false})
    .pipe(plumber())
    .pipe(anotherPlugin(opts))
    .pipe(gulp.dest('./html'))

options.name

Type: String
Default: undefined

Name of the watcher. If it present in options, you will get more readable output:

Naming watchers

options.verbose

Type: Boolean
Default: false

This options will enable more verbose output (useful for debugging).

options.silent

Type: Boolean
Default: false

This options will disable all output (useful for tests).

Methods

Returned Stream from constructor have some useful methods:

  • close() - calling gaze.close and emitting end, after gaze.close is done.

Events

  • end - all files are stop being watched.
  • ready - just re-emitted event from gaze.
  • error - when something happened inside callback, you will get notified.

Properties

  • gaze - instance of gaze in case you want to call it methods (for example remove). Be aware no one guarantee you nothing after you hacked on gaze.

Returns

Stream, that handles gulp.src piping.

License

MIT (c) 2013 Vsevolod Strukchinsky (floatdrop@gmail.com)

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