Register mce plugin scripts

[ellatrix]

TO DO: save with more than just the file name.

[ellatrix]

Something strange is going on with the main tinymce script, I think in master too. It always pops up and is then immediately removed again.

[aduth]

I saw an error about the missing lists script in my console this morning too. Does it work when loaded from the CDN? Curious if the script is varying plugin import logic by whether it's loaded off the filesystem.

[ellatrix]

@aduth That's the issue this PR fixes. When it's already loaded, tinymce will use that and not try to fetch the script itself. But I'm seeing something strange with the main script now.

[aduth]

My question was more of curiosity, maybe to a broader point of: are we going to encounter other resources TinyMCE will try to load by inferred path because it's assuming we have all scripts in the filesystem? Perhaps not.

[ellatrix]

are we going to encounter other resources TinyMCE will try to load by inferred path because it's assuming we have all scripts in the filesystem?

Not if we don't add any plugins or themes. If we do, we should register it. If a plugin does, they'll need to include it. Same for plugins and core currently.

[nylen]

I was a bit concerned about long paths here, due to potential Windows issues (example) and general non-human-friendliness. Addressed in the most recent few commits; I also added a constant to skip downloading these scripts during PHPUnit test runs because this is a bit slow.

Results with SCRIPT_DEBUG = true:

✓ james@xps15 <gutenberg> $ ls vendor/
react.3a8927d9.js      react-dom-server.e84b9fa6.js  tinymce-plugin-lists.557da104.js
react-dom.e5cfcfc9.js  tinymce.c847083c.js

Results with SCRIPT_DEBUG = false:

✓ james@xps15 <gutenberg> $ ls vendor/
react-dom.min.912dc6cf.js         react.min.c7397a88.js    tinymce-plugin-lists.min.e95f0005.js
react-dom-server.min.538e07c8.js  tinymce.min.04a1d751.js

[nylen]

Any objections to me merging this in the next day or so? It's a nice bugfix and a speed improvement to the PHPUnit build.

[ellatrix]

No objections really, I'm just finding it getting a lot of code to cache nightly scripts. :)

[nylen]

I'm not opposed to ripping it out later. For now we need it, though (it helps :alot: with slow/unreliable connections), and I'm thinking maybe we can re-use some of this machinery for release versions for example.