fix ValidationError.json() (#922)

changes/922-samuelcolvin.md

@@ -0,0 +1 @@
+Fix JSON serialization errors on `ValidationError.json()` by using `pydantic_encoder`

pydantic/error_wrappers.py

@@ -1,6 +1,7 @@
 import json
 from typing import TYPE_CHECKING, Any, Dict, Generator, List, Optional, Sequence, Tuple, Type, Union
 
+from .json import pydantic_encoder
 from .utils import Representation
 
 if TYPE_CHECKING:
@@ -53,7 +54,7 @@ class ValidationError(Representation, ValueError):
         return self._error_cache
 
     def json(self, *, indent: Union[None, int, str] = 2) -> str:
-        return json.dumps(self.errors(), indent=indent)
+        return json.dumps(self.errors(), indent=indent, default=pydantic_encoder)
 
     def __str__(self) -> str:
         errors = self.errors()

tests/test_main.py

@@ -443,6 +443,7 @@ def test_const_list_with_wrong_value():
             'type': 'value_error.const',
         },
     ]
+    assert exc_info.value.json().startswith('[')
 
     with pytest.raises(ValidationError) as exc_info:
         Model(a=[SubModel(b=3), SubModel(b=1), SubModel(b=2)], b=[SubModel(b=3), SubModel(b=1)])
@@ -464,6 +465,7 @@ def test_const_list_with_wrong_value():
             'type': 'value_error.const',
         },
     ]
+    assert exc_info.value.json().startswith('[')
 
 
 def test_const_validation_json_serializable():

tests/test_networks.py

@@ -247,6 +247,7 @@ def test_postgres_dsns():
     with pytest.raises(ValidationError) as exc_info:
         Model(a='http://example.org')
     assert exc_info.value.errors()[0]['type'] == 'value_error.url.scheme'
+    assert exc_info.value.json().startswith('[')
 
 
 def test_redis_dsns():

tests/test_types.py

@@ -1270,6 +1270,7 @@ def test_decimal_validation(type_, value, result):
         with pytest.raises(ValidationError) as exc_info:
             model(foo=value)
         assert exc_info.value.errors() == result
+        assert exc_info.value.json().startswith('[')
     else:
         assert model(foo=value).foo == result
 

tests/test_types_payment_card_number.py

@@ -86,5 +86,6 @@ def test_valid():
     ],
 )
 def test_error_types(card_number: Any, error_message: str):
-    with pytest.raises(ValidationError, match=error_message):
+    with pytest.raises(ValidationError, match=error_message) as exc_info:
         PaymentCard(card_number=card_number)
+    assert exc_info.value.json().startswith('[')