test: cover GroupLinkStatus' absent-collection fallback in the browser

tests/e2e-coverage-describe-gate.test.mjs

@@ -54,6 +54,7 @@ const COVERAGE_GATED = [
   'data-fixtures.spec.js',
   'data-variants.spec.js',
   'focus-trap-empty-dialog.spec.js',
+  'group-link-status-absent-groups.spec.js',
   'group-link-status-variant.spec.js',
   'member-directory-freshness-all-absent.spec.js',
   'member-directory-freshness-unlinked.spec.js',

tests/e2e-data-fixture-validity.test.mjs

@@ -138,6 +138,13 @@ const EXPECTED = new Map([
       adds: [],
     },
   ],
+  [
+    'data-no-revision/community-groups.json',
+    {
+      why: "clears the groups collection to reach GroupLinkStatus's `groupsData?.groups || []` fallback; the gate requires a non-empty collection, which is exactly the document an interrupted link-check run leaves behind",
+      adds: ['community-groups.json: groups must be a non-empty array'],
+    },
+  ],
   [
     'data-no-revision/members.json',
     {

tests/e2e/fixtures/data-no-revision/community-groups.json

@@ -0,0 +1,6 @@
+{
+  "description": "Clears the groups collection so GroupLinkStatus takes the `groupsData?.groups || []` fallback in src/components/GroupLinkStatus/index.js instead of filtering a real array. That arm is the component's guard against a partial data/community-groups.json -- `npm run check:community-group-links` writes the file in one pass, so an interrupted or failed run can leave the document without its collection -- and it is the only arm of the component no build reaches: the ordinary coverage build and tests/e2e/fixtures/data-variant/community-groups.json both carry groups, and a cleared collection cannot go in the variant build, which appends a second drifted group to reach the plural stale.length arms. It is set to null rather than [] because an empty array is truthy and would take the left operand, leaving the fallback unreached. It rides this build because nothing the no-revision build already covers reads community-groups.json, so it costs no additional Docusaurus compile (see the preamble of tests/tools/e2e-data-fixtures.cjs).",
+  "set": {
+    "groups": null
+  }
+}

tests/e2e/group-link-status-absent-groups.spec.js

@@ -0,0 +1,92 @@
+// End-to-end coverage for the absent-collection fallback in
+// src/components/GroupLinkStatus/index.js:
+//
+//   const stale = (groupsData?.groups || []).filter(...)
+//
+// The `|| []` operand is the component's guard against a
+// data/community-groups.json that carries no collection at all.
+// `npm run check:community-group-links` rewrites the document in one pass, so
+// a run that is interrupted, or that fails after truncating the file, can
+// leave the Community page a document without `groups`. The guard is what
+// makes that render the page without the drift warning rather than throw on
+// `undefined.filter` and take the whole route down.
+//
+// Why this is the one arm of the component no existing build reaches.
+// tests/e2e/group-link-status-variant.spec.js covers the plural drift arms
+// from the variant build, which *appends* a second drifted group, and the
+// ordinary coverage build appends one; both therefore carry `groups`, and the
+// left operand wins in each. Clearing the collection cannot go in either:
+// the variant build needs two drifted groups to render the plural grammar,
+// and the ordinary build is where the singular arm and the drift warning are
+// measured from. The shape rides tests/e2e/fixtures/data-no-revision/ because
+// nothing that build already covers reads community-groups.json, so it costs
+// no additional Docusaurus compile (see the preamble of
+// tests/tools/e2e-data-fixtures.cjs).
+//
+// The collection is cleared to null rather than to an empty array because an
+// empty array is truthy: `[] || []` takes the left operand and leaves the
+// fallback unreached.
+//
+// The real route is asserted beside the no-revision one. An assertion that a
+// page carries no drift warning passes just as well when the route 404s or
+// the build lost the page, so the pair is what makes it evidence that the
+// fallback supplied the empty collection rather than that nothing rendered.
+import { test, expect } from '../tools/e2e-coverage.cjs';
+import { loadSiteData } from '../tools/e2e-data-fixtures.cjs';
+
+const COMMUNITY_PATH = '/community';
+const NO_REVISION_BASE = '/e2e-coverage-no-revision';
+
+const COVERAGE_ENV = { E2E_COVERAGE: '1' };
+const NO_REVISION_ENV = {
+  E2E_COVERAGE: '1',
+  E2E_COVERAGE_BUILD: 'no-revision',
+};
+
+// Read through the overlays rather than hard-coded, so an edited fixture fails
+// here instead of leaving a test that asserts nothing.
+const groups = loadSiteData('community-groups.json', COVERAGE_ENV);
+const absentGroups = loadSiteData('community-groups.json', NO_REVISION_ENV);
+
+const isStale = (group) => group.archived || group.reachable === false;
+const UPDATED_LINE = /Upstream group status last updated on/;
+const DRIFT_WARNING = /archived or unreachable upstream/;
+
+// The no-revision site is only built by the coverage run; outside it the base
+// path does not exist.
+const describeCoverage =
+  process.env.E2E_COVERAGE === '1' ? test.describe : test.describe.skip;
+
+describeCoverage('a community-groups document carrying no collection', () => {
+  test('the drift warning is dropped rather than throwing on the missing collection', async ({
+    page,
+  }) => {
+    // The shapes the two pages are built from. Stated as assertions rather
+    // than used to skip: an overlay that stopped clearing the collection
+    // would leave the fallback unexercised, which is the silent retirement
+    // this pair exists to catch.
+    expect(Array.isArray(groups.groups)).toBe(true);
+    expect(groups.groups.filter(isStale).length).toBeGreaterThan(0);
+    expect(absentGroups.groups).toBe(null);
+    // The last-updated line is the evidence that the component rendered at
+    // all on the no-revision page, so it has to survive the cleared
+    // collection: generatedAt is left alone by this overlay.
+    expect(absentGroups.generatedAt).toEqual(groups.generatedAt);
+
+    await page.goto(COMMUNITY_PATH);
+    await expect(page.getByText(DRIFT_WARNING)).toBeVisible();
+
+    await page.goto(`${NO_REVISION_BASE}${COMMUNITY_PATH}`);
+    // The route built and served: the page's own heading is prose around the
+    // component, so it renders whether or not the corpus has anything to say.
+    await expect(
+      page.getByRole('heading', { name: 'Community', level: 1 }),
+    ).toBeVisible();
+    // The component itself still rendered -- this is an empty collection, not
+    // a page that lost the component or a build that lost the route.
+    await expect(page.getByText(UPDATED_LINE)).toBeVisible();
+    // ...and with nothing to report it says nothing, rather than reporting an
+    // empty list of drifted groups.
+    await expect(page.getByText(DRIFT_WARNING)).toHaveCount(0);
+  });
+});