fix: build the site before the CI test suite

.github/workflows/validate.yml

@@ -283,6 +283,13 @@ jobs:
         if: ${{ !cancelled() }}
         run: python scripts/generate_site.py
 
+      # website/dist is gitignored too. Built after the suite, the tests that
+      # read the rendered pages (page budgets, sidebar, search) found none and
+      # skipped on every run.
+      - name: Build the site
+        if: ${{ !cancelled() }}
+        run: npm run build --prefix website
+
       - name: Run test suite
         if: ${{ !cancelled() }}
         # No test downloads a release asset: 252 MB files fetched into the
@@ -302,11 +309,9 @@ jobs:
       # heading failed it there with nothing in front of it. Run whatever the
       # suite returned, so one red step does not hide the other. The release
       # assets are not restored: they change counts, not links or headings.
-      - name: Build the site
+      - name: Check the built site
         if: ${{ !cancelled() }}
-        run: |
-          npm run build --prefix website
-          python scripts/validate_site.py --site-dir website/dist
+        run: python scripts/validate_site.py --site-dir website/dist
 
   label-pr:
     runs-on: ubuntu-latest

tests/test_workflow_paths.py

@@ -142,6 +142,11 @@ class ThePullRequestBuildsTheSite(unittest.TestCase):
         )
         suite = next(i for i, run in enumerate(runs) if "unittest discover" in run)
         self.assertLess(generate, suite)
+        # The built pages too: about fifty tests read website/dist.
+        build = next(i for i, run in enumerate(runs) if "npm run build" in run)
+        self.assertLess(generate, build)
+        self.assertLess(build, suite)
+        self.assertEqual(steps[build].get("if"), "${{ !cancelled() }}")
         self.assertEqual(steps[suite].get("if"), "${{ !cancelled() }}")
         # A failed data fetch skipped the generator, and all 228 site tests
         # then failed under it: the generator runs whatever came before.