Use pickle

Author: nicoddemus

src/_pytest/subtests.py

@@ -11,7 +11,7 @@
 from contextlib import ExitStack
 from contextlib import nullcontext
 import dataclasses
-import json
+import pickle
 import time
 from types import TracebackType
 from typing import Any
@@ -64,24 +64,15 @@ class SubtestContext:
 
     def _to_json(self) -> dict[str, Any]:
         result = dataclasses.asdict(self)
-
-        # Best-effort to convert the kwargs values to JSON (pytest-dev/pytest-xdist#1273).
-        # If they can be converted, we return as it is, otherwise we return its saferepr because it seems
-        # this is the best we can do at this point.
-        def convert(x: Any) -> Any:
-            try:
-                json.dumps(x)
-            except TypeError:
-                return saferepr(x)
-            else:
-                return x
-
-        result["kwargs"] = {k: convert(v) for (k, v) in result["kwargs"].items()}
+        # Use protocol 0 because it is human-readable and guaranteed to be not-binary.
+        protocol = 0
+        data = pickle.dumps(result["kwargs"], protocol=protocol)
+        result["kwargs"] = data.decode("UTF-8")
         return result
 
     @classmethod
     def _from_json(cls, d: dict[str, Any]) -> Self:
-        return cls(msg=d["msg"], kwargs=d["kwargs"])
+        return cls(msg=d["msg"], kwargs=pickle.loads(d["kwargs"].encode("UTF-8")))
 
 
 @dataclasses.dataclass(init=False)

testing/test_subtests.py

@@ -5,7 +5,6 @@
 import sys
 from typing import Literal
 
-from _pytest._io.saferepr import saferepr
 from _pytest.subtests import SubtestContext
 from _pytest.subtests import SubtestReport
 import pytest
@@ -960,14 +959,17 @@ def test(subtests):
     )
 
 
+class MyEnum(Enum):
+    """Used in test_serialization, needs to be declared at the module level to be pickled."""
+
+    A = "A"
+
+
 def test_serialization() -> None:
     """Ensure subtest's kwargs are serialized using `saferepr` (pytest-dev/pytest-xdist#1273)."""
     from _pytest.subtests import pytest_report_from_serializable
     from _pytest.subtests import pytest_report_to_serializable
 
-    class MyEnum(Enum):
-        A = "A"
-
     report = SubtestReport(
         "test_foo::test_foo",
         ("test_foo.py", 12, ""),
@@ -984,7 +986,7 @@ class MyEnum(Enum):
     new_report = pytest_report_from_serializable(data)
     assert new_report is not None
     assert new_report.context == SubtestContext(
-        msg="custom message", kwargs=dict(i=10, a=saferepr(MyEnum.A))
+        msg="custom message", kwargs=dict(i=10, a=MyEnum.A)
     )
 
 
@@ -1010,5 +1012,6 @@ def test(self):
                     pass
         """
     )
+    pytester.syspathinsert()
     result = pytester.runpytest("-n1", "-pxdist.plugin")
     result.assert_outcomes(passed=2)