pytest.warns multiple argument handling

changelog/11906.bugfix.rst

@@ -0,0 +1 @@
+Fix regression with :func:`pytest.warns` using custom warning subclasses which have more than one parameter in their `__init__`.

src/_pytest/recwarn.py

@@ -322,10 +322,10 @@ def found_str():
             for w in self:
                 if not self.matches(w):
                     warnings.warn_explicit(
-                        str(w.message),
-                        w.message.__class__,  # type: ignore[arg-type]
-                        w.filename,
-                        w.lineno,
+                        message=w.message,
+                        category=w.category,
+                        filename=w.filename,
+                        lineno=w.lineno,
                         module=w.__module__,
                         source=w.source,
                     )
@@ -336,7 +336,9 @@ def found_str():
 
     @staticmethod
     def _validate_message(wrn: Any) -> None:
-        if not isinstance(msg := wrn.message.args[0], str):
+        if type(wrn.message) is UserWarning and not isinstance(
+            msg := wrn.message.args[0], str
+        ):
             raise TypeError(
                 f"Warning message must be str, got {msg!r} (type {type(msg).__name__})"
             )

testing/test_recwarn.py

@@ -504,3 +504,17 @@ def test_raise_type_error_on_non_string_warning_cpython() -> None:
         with warnings.catch_warnings():
             warnings.filterwarnings("ignore", "test")
             warnings.warn(1)  # type: ignore
+
+
+def test_multiple_arg_custom_warning() -> None:
+    """Test for issue #11906."""
+
+    class CustomWarning(UserWarning):
+        def __init__(self, a, b):
+            pass
+
+    with pytest.warns(CustomWarning):
+        with pytest.raises(pytest.fail.Exception, match="DID NOT WARN"):
+            with pytest.warns(CustomWarning, match="not gonna match"):
+                a, b = 1, 2
+                warnings.warn(CustomWarning(a, b))