Gulp 4: gulp.parallel will stop gulp immediately when one task fails

In the docs it is stated that gulp.parallel will still execute all tasks if an error occurs:

When the returned function is executed, the tasks or functions will be executed in parallel, all being executed at the same time. If an error occurs, all execution will complete.

This currently doesn’t seem to be the case as the following minimal code example will demonstrate:

var gulp = require('gulp')

gulp._settle = false

gulp.task('error', function(done) {
  setTimeout(function() {
    done(new Error('Somethings wrong!'))
  }, 200)
})

gulp.task('willnotfinish', function(done) {
  setTimeout(function() {
    console.log('I will never finish :(')
    done()
  }, 2000)
})

gulp.task('watch', function() {
  gulp.watch('watchme.js', gulp.parallel('default'))
})

gulp.task('default', gulp.parallel(
  'error',
  'willnotfinish'
))

This will stop running gulp after ~200ms with the following output and the task ‘willnotfinish’ will never finish executing:

Using gulpfile ~/Desktop/development/gulp-parallel-error/gulpfile.js
Starting 'default'...
Starting 'error'...
Starting 'willnotfinish'...
'error' errored after 204 ms
Error: Somethings wrong!
  at null._onTimeout (/Users/perplex/Desktop/development/gulp-parallel-error/gulpfile.js:5:10)
  at Timer.listOnTimeout (timers.js:92:15)
'default' errored after 211 ms
The following tasks did not complete: willnotfinish
Did you forget to signal async completion?

EDIT: Include watch task in code sample

[ulrichb]

The --continue switch is cool, but I would like to move this behavior change (of gulp.parallel()) into the gulpfile.js, and also scope it to a single parallel() sub-tree.

=> Any change to get this option into the API (e.g. gulp.parallel(..., { continue: true })?

An example use case is when executing linters in parallel: Then you don’t want to stop the execution if one linter emits errors (and you also want the output of all parallel executing linters). Also here you want to scope the --contine to just the linting-task (and not all the others).

[phated]

@ulrichb it’s not something we want people to use but you can “hack the system” by setting gulp._settle = true before calling gulp.parallel (because gulp is just an instance of Undertaker and that’s the property undertaker looks for). You could also have a separate “settle” instance by doing:

var settled = new gulp.Gulp();
settled._settle = true;

settled.parallel(...tasks);