Add diagnostics for flaky test_regrtest worker bug

youknowone · youknowone · commit d86ddd5b273e · 2026-03-05T02:00:45.000+09:00
When worker JSON parsing fails with AttributeError, include raw JSON
content and data keys in the error message to help diagnose the
intermittent 'TestResult object has no attribute state' failure.
diff --git a/Lib/test/libregrtest/result.py b/Lib/test/libregrtest/result.py
@@ -238,6 +238,15 @@ def _decode_test_result(data: dict[str, Any]) -> TestResult | dict[str, Any]:
             data['covered_lines'] = [
                 tuple(loc) for loc in data['covered_lines']
             ]
-        return TestResult(**data)
+        # TODO: RUSTPYTHON; diagnostics for flaky worker bug
+        try:
+            result = TestResult(**data)
+        except AttributeError:
+            raise AttributeError(
+                f"TestResult(**data) failed; keys={sorted(data.keys())}, "
+                f"slots={getattr(TestResult, '__slots__', 'N/A')}, "
+                f"data={data!r}"
+            )
+        return result
     else:
         return data
diff --git a/Lib/test/libregrtest/run_workers.py b/Lib/test/libregrtest/run_workers.py
@@ -347,7 +347,10 @@ def read_json(self, json_file: JsonFile, json_tmpfile: TextIO | None,
         except Exception as exc:
             # gh-101634: Catch UnicodeDecodeError if stdout cannot be
             # decoded from encoding
-            err_msg = f"Failed to parse worker process JSON: {exc}"
+            # TODO: RUSTPYTHON; include JSON for debugging flaky worker bugs
+            json_preview = worker_json[:500] if len(worker_json) > 500 else worker_json
+            err_msg = (f"Failed to parse worker process JSON: {exc}\n"
+                       f"  JSON ({len(worker_json)} bytes): {json_preview!r}")
             raise WorkerError(self.test_name, err_msg, stdout,
                               state=State.WORKER_BUG)
 
diff --git a/Lib/test/libregrtest/worker.py b/Lib/test/libregrtest/worker.py
@@ -110,6 +110,17 @@ def worker_process(worker_json: StrJSON) -> NoReturn:
                 "`test.cov` not found in sys.modules but coverage wanted"
             )
 
+    # TODO: RUSTPYTHON; diagnostics for flaky worker bug
+    # Verify TestResult attributes are accessible before JSON encoding
+    try:
+        _ = result.state
+        _ = result.test_name
+    except AttributeError as e:
+        print(f"WORKER BUG: TestResult slot access failed before encoding: {e}",
+              file=sys.stderr, flush=True)
+        print(f"  result type: {type(result)}, slots: {getattr(type(result), '__slots__', 'N/A')}",
+              file=sys.stderr, flush=True)
+
     if json_file.file_type == JsonFileType.STDOUT:
         print()
         result.write_json_into(sys.stdout)
