Fix gulp watch task

[lb-]

• revise watch & task syntax for Gulp v4 requirements (regression from upgrading to v4)
• to validate; run npm run start and make a change to a scss or js file - expectation is that the relevant build task should run and refreshing the browser should reflect that change

[squash-labs]

Manage this branch in Squash

Test this branch here: https://lb-fixgulp-watch-v4-regression-9kqrr.squash.io

[zerolab]

Kudos @lb- !

I did scratch my head at the en of last week when I needed to do some style changes and watch was not reacting.

Tried this locally and watch is back working again. It does, interestingly, start 9 threads of styles:sass when saving a single scss file. I wonder if that is by design or there's a tweak that can be made

[lb-]

Hmm. Good point. Maybe the series for each should be parallel, from what I read the old syntax would do series.

Not sure if this used to work the same with multiple threads of scams builds.

I also noticed it seems to take a while, 30s on my VM.

I have not had much experience with full config so not sure what else to try.

@zerolab

[lb-]

@zerolab can you give it another try, I have consolidated all the watchers that get generated, hopefully this will be better.

[zerolab]

🎉 that does it!

$ npm run watch
...
[09:23:34] Finished 'build' after 3.61 s

// modify and save an scss file
[09:23:34] Starting '<anonymous>'...
[09:23:50] Starting 'styles:sass'...
[09:23:52] Wagtail CSS all files 143.84 kB
[09:23:52] Finished 'styles:sass' after 1.4 s

// undo change, save
[09:24:00] Starting 'styles:sass'...
[09:24:01] Wagtail CSS all files 143.84 kB
[09:24:01] Finished 'styles:sass' after 1.09

[zerolab]

Merged. Thank you @lb-

[lb-]

Awesome thanks @zerolab