Rework WP_Scripts to support named groups

[westi]

Currently WP_Scripts has some "special" code for splitting things across header and footer and concatenating core scripts.

I would like to change it to support the following:

• Named Groups - so we can have header, footer, ...
• L10N awareness - so we can auto output the l10n.js file first if we need it - XRef #15124
• Concatenation opt-out
• Concatentaion opt-in for plugins.

I was working on this for #15124 until it became apparent that it wasn't right to do it for 3.1 - not enough time to fully test.

To think about: ​http://headjs.com/

Replying to westi:

To think about: ​http://headjs.com/

I spent an evening hacking together a plugin that extends WP_Scripts to use head.js rather than individual script tags. It worked in the sense that it caused the page to load without blocking for the scripts. However, it broke several of the most basic scripted function such as the collapsing admin menus.

We commonly use inline scripts with the assumption that dependencies are already loaded. When loading scripts with head.js, you can't assume this. The fix is simple: wrap the script in a head.js call that delays execution until the dependency is fulfilled. You can still use inline scripts; you just have to take this little extra step (for which we could build helpers into WP_Scripts/WP_Dependencies).

<script>
// call a function assuming jQuery Tools is loaded
jQuery(".tip").tooltip();
</script>

<script>
// call a function immediately after jQuery Tools is loaded
head.ready("tools", function() {
   $(".tip").tooltip();
});
</script>

It is possible to use script concatenation with head.js but I don't think it has facilities for one script to fulfill multiple dependencies. I have created an ​issue on the head.js project on GitHub.

Removing 3.2-early tag this didn't make the feature cut for 3.2