Support WPT subsuites in agregating and flake detection (#37584)

Handle subsuites in wpt flake detection and aggregation as outlined in
https://github.com/servo/servo/issues/37319#issuecomment-2969528022.
Based on #37540.

Testing: Manual CI run with vello_canvas subsuite:
https://github.com/sagudev/servo/actions/runs/16021200215

---------

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

etc/ci/report_aggregated_expected_results.py

@@ -99,16 +99,7 @@ class Item:
         return result
 
 
-def get_results(filenames: list[str], tag: str = "") -> Optional[Item]:
-    unexpected = []
-    for filename in filenames:
-        try:
-            with open(filename, encoding="utf-8") as file:
-                unexpected += json.load(file)
-        except FileNotFoundError as exception:
-            print(exception)
-    unexpected.sort(key=lambda result: result["path"])
-
+def get_results(unexpected: list[dict], tag: str = "") -> Optional[Item]:
     def is_flaky(result):
         return result["flaky"]
 
@@ -141,6 +132,27 @@ def get_results(filenames: list[str], tag: str = "") -> Optional[Item]:
     return Item(text, "", children) if children else None
 
 
+def get_results_per_subsuite(filenames: list[str], tag: str = "") -> list[tuple[Item, str]]:
+    unexpected = []
+    for filename in filenames:
+        try:
+            with open(filename, encoding="utf-8") as file:
+                unexpected += json.load(file)
+        except FileNotFoundError as exception:
+            print(exception)
+    unexpected.sort(key=lambda result: result["path"])
+    subsuites = set(result.get("subsuite", "") for result in unexpected)
+    results = []
+    for subsuite in subsuites:
+        tag = f"{tag} {subsuite}" if subsuite else tag
+        subsuite_results = get_results(
+            list(filter(lambda result: result.get("subsuite", "") == subsuite, unexpected)), tag
+        )
+        if subsuite_results:
+            results.append((subsuite_results, tag))
+    return results
+
+
 def get_github_run_url() -> Optional[str]:
     github_context = json.loads(os.environ.get("GITHUB_CONTEXT", "{}"))
     if "repository" not in github_context:
@@ -244,23 +256,24 @@ def main():
     parser = argparse.ArgumentParser()
     parser.add_argument("--tag", default="wpt", action="store", help="A string tag used to distinguish the results.")
     args, filenames = parser.parse_known_args()
-    results = get_results(filenames, args.tag)
+    results = get_results_per_subsuite(filenames, args.tag)
     if not results:
         print("Did not find any unexpected results.")
         create_github_reports("Did not find any unexpected results.", args.tag)
         return
 
-    print(results.to_string())
+    for subsuite_results, subsuite_tag in results:
+        print(subsuite_results.to_string())
 
-    html_string = ElementTree.tostring(results.to_html(), encoding="unicode")
-    create_github_reports(html_string, args.tag)
+        html_string = ElementTree.tostring(subsuite_results.to_html(), encoding="unicode")
+        create_github_reports(html_string, subsuite_tag)
 
-    pr_number = get_pr_number()
-    if pr_number:
-        process = subprocess.Popen(["gh", "pr", "comment", pr_number, "-F", "-"], stdin=subprocess.PIPE)
-        print(process.communicate(input=html_string.encode("utf-8"))[0])
-    else:
-        print("Could not find PR number in environment. Not making GitHub comment.")
+        pr_number = get_pr_number()
+        if pr_number:
+            process = subprocess.Popen(["gh", "pr", "comment", pr_number, "-F", "-"], stdin=subprocess.PIPE)
+            print(process.communicate(input=html_string.encode("utf-8"))[0])
+        else:
+            print("Could not find PR number in environment. Not making GitHub comment.")
 
 
 if __name__ == "__main__":

python/wpt/grouping_formatter.py

@@ -34,6 +34,7 @@ class UnexpectedSubtestResult:
 @dataclass
 class UnexpectedResult:
     path: str
+    subsuite: str
     actual: str
     expected: str
     message: str
@@ -185,6 +186,7 @@ class ServoHandler(mozlog.reader.LogHandler):
         self.completed_tests += 1
         test_status = data["status"]
         test_path = data["test"]
+        test_subsuite = data["subsuite"]
         del self.running_tests[data["thread"]]
 
         had_expected_test_result = self.data_was_for_expected_result(data)
@@ -211,6 +213,7 @@ class ServoHandler(mozlog.reader.LogHandler):
         if self.currently_detecting_flakes:
             return UnexpectedResult(
                 test_path,
+                test_subsuite,
                 test_status,
                 data.get("expected", test_status),
                 data.get("message", ""),
@@ -229,6 +232,7 @@ class ServoHandler(mozlog.reader.LogHandler):
 
         result = UnexpectedResult(
             test_path,
+            test_subsuite,
             test_status,
             data.get("expected", test_status),
             data.get("message", ""),