Improve and simplify Gulp

[domoscargin]

What

Simplify our use of Gulp by reducing its use to task running. Write our own scripts for the actual tasks, which do not rely on Gulp.

Why

Our gulp tasks are complicated and doing too many things: #2243

Additionally, we cannot update a lot of dependencies because of our reliance on oldie: #2469

We had previously made the decision to move away from Gulp and write our own build scripts.

We essentially removed all Gulp usage, then changed our mind with some exceptions

Composed build tasks can use Gulp

1. Build targets in tasks/build/** for ./dist and ./package
2. Review app builds in app/tasks/build/** for ./app/dist

But since every Gulp task such as npx gulp build:package has a corresponding npm run build:package we chose not to document these in tasks.md

Composed build tasks need logging

But then we realised we lost logging in the terminal so brought some Gulp usage back:

• Limiting gulp.parallel() and gulp.series() for composed build tasks only
• Limiting gulp.task() usage to gulpfile.mjs configs only

Shared tasks without Gulp

But last of all, we split out all the Review app tasks in #3384 which gave us the opportunity to make all shared tasks work without Gulp. We switched to the export your tasks pattern vs using gulp.task()

Reminder: This API isn't the recommended pattern anymore - export your tasks.

All our new tasks are now plain async functions:

await files.copy('**/*', {
  srcPath: join(paths.src, 'govuk/assets'),
  destPath: join(paths.app, 'dist/assets')
})

Yet they can still be composed into tasks for Gulp's gulp.series() and gulp.parallel() etc

task.name('copy:assets', () => files.copy('**/*', {
  srcPath: join(paths.src, 'govuk/assets'),
  destPath: join(paths.app, 'dist/assets')
}))

Who needs to work on this

Developers

Who needs to review this

Developers

Done when

• Refactor sassdoc task to remove Gulp #2708
• Refactor nodemon task to remove Gulp #2709
• Refactor asset version task to remove Gulp #2715
• Refactor clean task to remove Gulp #2714
• Decide on an approach to gulp-free task scripting #2779
• Refactor linting tasks to remove Gulp #2710
• Refactor file copying tasks to remove Gulp #2711
• Refactor standard compile tasks to remove Gulp #2712
• Remove IE8 Gulp compile tasks #2713
• Remove dependency on gulp in heroku NPM script #2768
• Refactor watch task to remove Gulp #2707
• Refactor gulpfile.js to remove use of Gulp #2716
• Update documentation on tasks #2772

[domoscargin]

@colinrotherham

Is there any undocumented work which might be outstanding here? Or should we go ahead and close this sucker?

[colinrotherham]

@domoscargin I think we're still missing those lost edits that captured why we're keeping Gulp

We essentially removed all Gulp usage, then changed our mind with some exceptions

Composed build tasks can use Gulp

1. Build targets in tasks/build/** for ./dist and ./package
2. Review app builds in app/tasks/build/** for ./app/dist

But since every Gulp task such as npx gulp build:package has a corresponding npm run build:package we chose not to document these in tasks.md

Composed build tasks need logging

But then we realised we lost logging in the terminal so brought some Gulp usage back:

• Limiting gulp.parallel() and gulp.series() for composed build tasks only
• Limiting gulp.task() usage to gulpfile.mjs configs only

Shared tasks without Gulp

But last of all, we split out all the Review app tasks in #3384 which gave us the opportunity to make all shared tasks work without Gulp. We switched to the export your tasks pattern vs using gulp.task()

Reminder: This API isn't the recommended pattern anymore - export your tasks.

All our new tasks are now plain async functions:

await files.copy('**/*', {
  srcPath: join(paths.src, 'govuk/assets'),
  destPath: join(paths.app, 'dist/assets')
})

Yet they can still be composed into tasks for Gulp's gulp.series() and gulp.parallel() etc

task.name('copy:assets', () => files.copy('**/*', {
  srcPath: join(paths.src, 'govuk/assets'),
  destPath: join(paths.app, 'dist/assets')
}))

[domoscargin]

I've updated the description to reflect the changes to our approach.

And with that, I'm going to call this one done!