Add Perl script to list JS dependencies and suggest a load order

[nylen]

I wrote this script while I was working on #929 to better understand the dependencies between our various Webpack bundles. I'm not sure that we want to add this to the repo or not, but it was useful to me to determine the needed order of these modules in our Webpack config. (This is mainly important for the test build, as in the actual plugin this is handled via WP's script dependency resolution mechanism).

It's a bit unfortunate that we have to do this twice (once on the client side and once on the server side). However, I'm also thinking that this script (or something like it) will come in handy to calculate actual dependencies when we start adding more Webpack-built files to WP core.

[nylen]

I meant to include example output here as well:

$ bin/list-js-dependencies.pl 
'blocks' depends on 'components'
'blocks' depends on 'element'
'blocks' depends on 'i18n'
'blocks' depends on 'utils'
'components' depends on 'element'
'components' depends on 'i18n'
'editor' depends on 'blocks'
'editor' depends on 'components'
'editor' depends on 'date'
'editor' depends on 'element'
'editor' depends on 'i18n'
'editor' depends on 'utils'

Suggested load order:

element
i18n
components
utils
blocks
date
editor

A more robust version of this task would actually parse the JS files instead of just looking for a regex like from '(blocks|component|date|....

[aduth]

Are we depending on a specific load order?

[nylen]

Yes. On the server this is handled by registering script dependencies via WordPress's standard mechanism; also, the test build will break if the entry points in the Webpack config are rearranged sufficiently.

I'm fine with closing this out and saving the script that way. I opened a PR because I found it useful, and it may be more useful in the future.

[aduth]

I'm indifferent. Fine with merging, or as Gist territory.

[nylen]

This can live at https://gist.github.com/nylen/e9bcda0ee6c2c21e9f0063d9cdebd7e9.

[nylen]

This script still comes in handy occasionally (#2205). I've also updated the gist above for the recent changes to our import syntax in #2172.