test(acpmux): bare-pr-refs gives the code block's highlighter customElements, so it never fails on a slow runner

Merged
TE
17d ago
+20-2

Problem

webviews/test/bare-pr-refs.test.tsx "a reference in a code span or a code block is not a link" failed on #23212's CI run with:

ReferenceError: customElements is not defined
  at node_modules/@pierre/diffs/dist/components/web-components.js:6:43

The test's jsdom shim installs HTMLElement but not customElements. The code block's highlighted card (HighlightedCode.tsx, which imports @pierre/diffs) loads lazily after the first frame (CodeBlock.tsx loadHighlightedCode), and the library registers its web component at import time. On a slow runner that import settles while the test is still running, so it fails. On a fast host it settles after the test, so it passes. That's why the eight latest base runs pass it. The test came from #22893.

Change

Test only.

  1. The test awaits loadHighlightedCode(), so the import always lands inside it. The red is then the same on every host.
  2. The shim installs customElements from jsdom, and restores it after the test.

No assertion changes.

Changelog

none

Observed / Not run

  • bun test test/bare-pr-refs.test.tsx: with commit 1 alone, 3 pass and 1 fail (ReferenceError: customElements is not defined, CI's error). With commit 2: 4 pass.
  • Not run: CI on this head (pending).

Agent session: huge-blue

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Summary by cubic

Fixes the flaky bare-pr-refs test that failed on slow CI runners with ReferenceError: customElements is not defined. The code block's highlighted card lazily imports @pierre/diffs, which registers its web component at import time and builds its lines with the DOM's constructors. On slow hosts that import could land mid-test; on fast hosts it landed after.

The test now awaits loadHighlightedCode() so the import always settles inside the test, then reads the code block where the card draws it—in the diffs-container shadow root—and asserts no link appears there. The jsdom shim installs customElements plus all DOM constructors (HTML*, SVG*, CSS*, Shadow*, Document*) and restores them afterward. No assertion changes.