MessageCommand with no announce option announces message type

Nice catch. Silent movies with the VoiceOver caption window are good.

1. From #8
   

   Copy /core/modules/system/tests/modules/ajax_test to /modules/

   I am pleased to be able to mention that it is possible to run test modules without copying them to another directory. Add $settings['extension_discovery_scan_tests'] = TRUE; to settings.php.

2. Create a failing test-only patch that expands MessageCommandTest to confirm the message wrapper doesn't have a role attribute is empty when MessageCommand with 'announce' => '' is executed, and of course add that test to the main patch as well.

4. +++ b/core/misc/message.es6.js
   @@ -231,19 +231,23 @@
   +    if (announce !== '') {
   +      messageWrapper.setAttribute(
   +        'role',
   +        type === 'error' || type === 'warning' ? 'alert' : 'status',
   +      );
   +    }
   

   Provide a comment explaining why the role isn't set on an empty string (this can be deduced from the param description, but would be good to have here to mitigate future dev confusion)

While testing this I also noticed that most messages are read twice because they are sent to announce via add(), after which they are added to an element with an ARIA role defined. This usually doesn't happen with 'alert' as the alert kicks out the other attempt to announce the message, but I can make those occur twice in some instances with a throttled network connection. This will need a followup issue.

+++ b/core/misc/message.es6.js
@@ -231,19 +231,34 @@
+    // still be read when the element is added to the page.  To prevent that

Ubernit: there should only be one space separating the sentences.

Other than that, I think the changes are good. I added the tag "needs subsystem maintainer" since this modifies Drupal.message a bit. Not sure which jurisdiction this is, but I know @lauriii was active in the initial development of the JS messages API.

I've tried to test this manually.

There are some extra buttons in the video that aren't in the test module. May be the extra buttons need to be added as well?

Clicking the "Make Warning Message" button still announces "Warning message I am a warning message in the default location." From the description and test instructions from comment #8, I don't think that this is intended

Setting back to needs work.