Make repr work for instances that failed initialization when handling ValidationErrors

pydantic/main.py

@@ -878,7 +878,11 @@ def __repr_args__(self) -> _repr.ReprArgs:
             field = self.model_fields.get(k)
             if field and field.repr:
                 yield k, v
-        pydantic_extra = self.__pydantic_extra__
+        # `__pydantic_extra__` can fail to be set if the model is not yet fully initialized.
+        # This can happen if a `ValidationError` is raised during initialization and the instance's
+        # repr is generated as part of the exception handling. Therefore, we use `getattr` here
+        # with a fallback, even though the type hints indicate the attribute will always be present.
+        pydantic_extra = getattr(self, '__pydantic_extra__', None)
         if pydantic_extra is not None:
             yield from ((k, v) for k, v in pydantic_extra.items())
         yield from ((k, getattr(self, k)) for k, v in self.model_computed_fields.items() if v.repr)

tests/test_edge_cases.py

@@ -2559,3 +2559,38 @@ class Model(BaseModel):
     m = Model(a=bytes, b=int)
     assert m.model_dump() == {'a': bytes, 'b': int}
     assert m.a == bytes
+
+
+def test_custom_exception_handler():
+    from traceback import TracebackException
+
+    from pydantic import BaseModel
+
+    traceback_exceptions = []
+
+    class MyModel(BaseModel):
+        name: str
+
+    class CustomErrorCatcher:
+        def __enter__(self):
+            return None
+
+        def __exit__(self, _exception_type, exception, exception_traceback):
+            if exception is not None:
+                traceback_exceptions.append(
+                    TracebackException(
+                        exc_type=type(exception),
+                        exc_value=exception,
+                        exc_traceback=exception_traceback,
+                        capture_locals=True,
+                    )
+                )
+
+                return True
+            return False
+
+    with CustomErrorCatcher():
+        data = {'age': 'John Doe'}
+        MyModel(**data)
+
+    assert len(traceback_exceptions) == 1