run-sequence

Runs a sequence of gulp tasks in the specified order. This function is designed to solve the situation where you have defined run-order, but choose not to or cannot use dependencies.

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Each argument to run-sequence is run in order. This works by listening to the task_stop and task_err events, and keeping track of which tasks have been completed. You can still run some of the tasks in parallel, by providing an array of task names for one or more of the arguments.

If the final argument is a function, it will be used as a callback after all the functions are either finished or an error has occurred.

Please Note

This was intended to be a temporary solution until the release of gulp 4.0 which should have support for defining task dependencies similarly.

Given that Gulp 4 appears to never be fully released, take that for what you will. Be aware that this solution is a hack, and may stop working with a future update to gulp.

Usage

First, install run-sequence as a development dependency:

npm install --save-dev run-sequence

Then add use it in your gulpfile, like so (note these are only examples, please check the documentation for your functions for the correct way to use them):

var gulp = require('gulp');
var runSequence = require('run-sequence');
var del = require('del');
var fs = require('fs');

// This will run in this order:
// * build-clean
// * build-scripts and build-styles in parallel
// * build-html
// * Finally call the callback function
gulp.task('build', function(callback) {
  runSequence('build-clean',
              ['build-scripts', 'build-styles'],
              'build-html',
              callback);
});

// configure build-clean, build-scripts, build-styles, build-html as you wish,
// but make sure they either return a stream or promise, or handle the callback
// Example:

gulp.task('build-clean', function() {
    // Return the Promise from del()
    return del([BUILD_DIRECTORY]);
//  ^^^^^^
//   This is the key here, to make sure asynchronous tasks are done!
});

gulp.task('build-scripts', function() {
    // Return the stream from gulp
    return gulp.src(SCRIPTS_SRC).pipe(...)...
//  ^^^^^^
//   This is the key here, to make sure tasks run to completion!
});

gulp.task('callback-example', function(callback) {
    // Use the callback in the async function
    fs.readFile('...', function(err, file) {
        console.log(file);
        callback();
//      ^^^^^^^^^^
//       This is what lets gulp know this task is complete!
    });
});

Using within gulp submodules

If you have a complex gulp setup with your tasks split up across different files, you may get the error that run-sequence is unable to find your tasks. In this case, you can configure run-sequence to look at the gulp within the submodule, like so:

// submodule tasks/mygulptask.js

var gulp = require('gulp'), // might be a different instance than the toplevel one
    // this uses the gulp you provide
    runSequence = require('run-sequence').use(gulp);
    
    // ...and then use normally
    runSequence('subtask1', 'subtask2');

Options

There are a few global options you can configure on the runSequence function.

Please note these are global to the module, and once set will affect every use of runSequence.

Usage:

var runSequence = require('run-sequence');
runSequence.options.ignoreUndefinedTasks = true;
gulp.task('task', function(cb) {
	runSequence('foo', null, 'bar'); // no longer errors on `null`
})

• showErrorStackTrace: When set to false, this suppresses the full stack trace from errors captured during a sequence.
• ignoreUndefinedTasks: When set to true, this enables you to pass falsey values in which will be stripped from the task set before validation and sequencing.

LICENSE

MIT License