Add @wordpress/a11y script module

[sirreal]

Add a new @wordpress/a11y Script Module. The Script Module has the same API as the wp-a11y WP Script.

This implements Gutenberg PRs WordPress/gutenberg#65101 and WordPress/gutenberg#65380 to add the @wordpress/a11y Script Module in Core.

One difference with the wp-a11y WP Script is that the necessary HTML is injected into the initial page's HTML. The Script injects some elements into the DOM when loaded. This is problematic with accessibility live regions and modules that may have deferred loading. The background and justification for this change was discussed in WordPress/gutenberg#65380.

The script and module do not conflict. If the script is loaded, it will not inject elements into the DOM but will re-use the HTML rendered for the module. There is some potential for conflict if the live regions are used simultaneously by the script and module, but this has always been the case if different consumers use the script simultaneously.

#7304 and WordPress/gutenberg#65539 leverage the new @wordpress/a11y Script Module in the @wordpress/interactivity-router script module.

Testing

This can be tested by adding a dependency on @wordpress/a11y from another script module. The exposed speak function should work when the module is imported dynamically or statically.

If the wp-a11y script is also enqueued, no duplicate live regions should be injected into the DOM. Both the script's and the module's speak function should work correctly.

It can be helpful to observe a something like this in the browser console:

[...document.querySelectorAll('[aria-live]')].map(e => `${e.ariaLive}: ${JSON.stringify(e.textContent)}`)

For example:

(await import('@wordpress/a11y')).speak('Hello, ', 'assertive');
// ['assertive: "Hello, "', 'polite: ""']
wp.a11y.speak('world!');
// ['assertive: ""', 'polite: "world!"']

Trac ticket: https://core.trac.wordpress.org/ticket/60647

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[github-actions]

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[github-actions]

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Props jonsurrell, gziolo, czapla.

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[sirreal]

I don't love this, but as a private property I'm not too worried. I wanted to avoid iterating over the enqueued modules and the dependency graph repeatedly and this property allowed for pre-existing iteration to be used.

Perhaps when https://core.trac.wordpress.org/ticket/60597 is addressed a method like ::is_available( '@wordpress/a11y' ) could be implemented to know whether the module will be "available" (enqueued or in the import map).

[sirreal]

@gziolo @DAreRodz @michalczaplinski this is ready for review.

It can't be tested with #7304 at this time unless interactivity-router the package is modified in node_modules to modify this check.

[michalczaplinski]

This looks good to me! 👍

I've also tested it with a simple custom block using the @wordpress/a11y module:

view.js of my custom block

import { store, getContext } from "@wordpress/interactivity";

store("create-block", {
  actions: {
    toggle: () => {
      const context = getContext();
      context.isOpen = !context.isOpen;
    },
  },
  callbacks: {
    logIsOpen: function* () {
      const { isOpen } = getContext();

      const { speak } = yield import("@wordpress/a11y");

      console.log("isOpen", isOpen);

      if (isOpen) {
        speak("toggle open", "assertive");
      } else {
        speak("toggle closed", "assertive");
      }
    },
  },
});

output_2278ef.mp4

[michalczaplinski]

Committed via https://core.trac.wordpress.org/changeset/59089