Support web-platform-tests heuristics for test selection

Fixes #5481

Author: marco-c

bugbug/test_scheduling.py

@@ -1003,4 +1003,32 @@ def collect_support_files(value):
                         if f.is_file()
                     )
 
+        # If a web-platform test or meta is modified, run the relevant web-platform folder.
+        if not any(path.endswith(ignore) for ignore in ("/META.yml", "/README.md")):
+            for base in ("testing/web-platform/mozilla", "testing/web-platform"):
+                if path.startswith(f"{base}/meta/") or path.startswith(
+                    f"{base}/tests/"
+                ):
+                    sub = "meta" if "/meta/" in path else "tests"
+
+                    relative = Path(path).relative_to(f"{base}/{sub}")
+
+                    test_root = repo_dir / base / "tests"
+                    cur_dir = test_root / relative.parent
+
+                    def has_html_files(d: Path) -> bool:
+                        return any(p.suffix.lower() == ".html" for p in d.iterdir())
+
+                    while cur_dir != test_root and not has_html_files(cur_dir):
+                        cur_dir = cur_dir.parent
+
+                    # Ignore files in top level "meta" or "tests".
+                    if len(cur_dir.parts) == 1:
+                        break
+
+                    if has_html_files(cur_dir):
+                        manifests.add(str(cur_dir.relative_to(repo_dir)))
+
+                    break
+
     return manifests

tests/test_test_scheduling.py

@@ -1114,3 +1114,78 @@ def test_find_manifests_for_paths(tmp_path) -> None:
     assert test_scheduling.find_manifests_for_paths(
         str(tmp_path), ["absolute_path_with_subdirglob/subdir/asd.js"]
     ) == {"test/chrome.toml"}
+
+    (tmp_path / "testing/web-platform/tests/html/semantics").mkdir(parents=True)
+    (tmp_path / "testing/web-platform/tests/.gitignore").touch()
+    (
+        tmp_path
+        / "testing/web-platform/tests/html/semantics/rellist-feature-detection.html"
+    ).touch()
+    (tmp_path / "testing/web-platform/tests/html/semantics/META.yml").touch()
+    (tmp_path / "testing/web-platform/tests/html/semantics/interactive-elements").mkdir(
+        parents=True
+    )
+    (
+        tmp_path
+        / "testing/web-platform/tests/html/semantics/interactive-elements"
+        / "contextmenu-historical.html"
+    ).touch()
+    (tmp_path / "testing/web-platform/mozilla/meta/pointerevents").mkdir(parents=True)
+    (
+        tmp_path
+        / "testing/web-platform/mozilla/meta/pointerevents/pointerevent_click_during_parent_capture.html.ini"
+    ).touch()
+    (tmp_path / "testing/web-platform/mozilla/tests/pointerevents").mkdir(parents=True)
+    (
+        tmp_path
+        / "testing/web-platform/mozilla/tests/pointerevents/pointerevent_click_during_parent_capture.html"
+    ).touch()
+    (tmp_path / "testing/web-platform/tests/encrypted-media/content").mkdir(
+        parents=True
+    )
+    (
+        tmp_path
+        / "testing/web-platform/tests/encrypted-media/clearkey-events.https.html"
+    ).touch()
+    (
+        tmp_path
+        / "testing/web-platform/tests/encrypted-media/content/content-metadata.js"
+    ).touch()
+
+    assert (
+        test_scheduling.find_manifests_for_paths(
+            str(tmp_path), ["testing/web-platform/tests/.gitignore"]
+        )
+        == set()
+    )
+
+    assert test_scheduling.find_manifests_for_paths(
+        str(tmp_path),
+        ["testing/web-platform/tests/html/semantics/rellist-feature-detection.html"],
+    ) == {"testing/web-platform/tests/html/semantics"}
+
+    assert (
+        test_scheduling.find_manifests_for_paths(
+            str(tmp_path), ["testing/web-platform/tests/html/semantics/META.yml"]
+        )
+        == set()
+    )
+
+    assert test_scheduling.find_manifests_for_paths(
+        str(tmp_path),
+        [
+            "testing/web-platform/tests/html/semantics/interactive-elements/contextmenu-historical.html"
+        ],
+    ) == {"testing/web-platform/tests/html/semantics/interactive-elements"}
+
+    assert test_scheduling.find_manifests_for_paths(
+        str(tmp_path),
+        [
+            "testing/web-platform/mozilla/meta/pointerevents/pointerevent_click_during_parent_capture.html.ini"
+        ],
+    ) == {"testing/web-platform/mozilla/tests/pointerevents"}
+
+    assert test_scheduling.find_manifests_for_paths(
+        str(tmp_path),
+        ["testing/web-platform/tests/encrypted-media/content/content-metadata.js"],
+    ) == {"testing/web-platform/tests/encrypted-media"}