Best-effort to convert to JSON

Author: nicoddemus

src/_pytest/subtests.py

@@ -11,6 +11,7 @@
 from contextlib import ExitStack
 from contextlib import nullcontext
 import dataclasses
+import json
 import time
 from types import TracebackType
 from typing import Any
@@ -63,8 +64,15 @@ class SubtestContext:
 
     def _to_json(self) -> dict[str, Any]:
         result = dataclasses.asdict(self)
-        # Brute-force the returned kwargs dict to be JSON serializable (pytest-dev/pytest-xdist#1273).
-        result["kwargs"] = {k: saferepr(v) for (k, v) in result["kwargs"].items()}
+
+        # Best-effort to convert the kwargs values to JSON (pytest-dev/pytest-xdist#1273).
+        def convert(x: Any) -> str:
+            try:
+                return json.dumps(x)
+            except TypeError:
+                return saferepr(x)
+
+        result["kwargs"] = {k: convert(v) for (k, v) in result["kwargs"].items()}
         return result
 
     @classmethod