After this week's Codex release rides the MW train, we should test that things work as expected in the context of a consuming MW extension.

Test steps

The CodexExample extension has already been updated to use the new codexComponents option in its extension.json. With the latest version of CodexExample installed, it is possible to navigate to Special:CodexExample and see the following:

The screenshot above, captured before the patch that fixes T351753 has been released. The broken styles on the TypeaheadSearch component at the top of the page are clearly visible.

After the release of Codex 1.2.1 (scheduled for tomorrow – Jan 9), this problem should go away.

Acceptance criteria

• Loading the Codex bundle as part of the special page should not break the styling of the TypeaheadSearch widget (which is loaded as part of Vector).

Current status

As of Friday Jan 12 (after the release of Codex 1.2.1), I can see that the most egregious form of the breakage has been fixed.
However, it still looks like the TypeaheadSearch styles are slightly off – note the border radius on the top left corner of the drop-down menu after code-splitting bundles have been loaded:

This is how the TypeaheadSearch component looks on a page where code splitting is not used (this is the correct appearance):

Looks like the TypeaheadSearch menu styles needed the extra specificity treatment:

// before
.cdx-typeahead-search {
    &__menu {}
}

// should be
.cdx-typeahead-search {
    &__menu.cdx-menu {}
}

This patch should fix the issue.