apply update_forward_refs to json_encoders (#3595)

* apply update_forward_refs to json_encoders, fix #3583

* linting

* mypy

* avoid use of ForwardRef with python3.6

* fix ForwardRef usage, take 2

* coverage

changes/3583-samuelcolvin.md

@@ -0,0 +1 @@
+Apply `update_forward_refs` to `Config.json_encodes` prevent name clashes in types defined via strings.

pydantic/config.py

@@ -59,7 +59,8 @@ class BaseConfig:
     schema_extra: Union[Dict[str, Any], 'SchemaExtraCallable'] = {}
     json_loads: Callable[[str], Any] = json.loads
     json_dumps: Callable[..., str] = json.dumps
-    json_encoders: Dict[Type[Any], AnyCallable] = {}
+    # key type should include ForwardRef, but that breaks with python3.6
+    json_encoders: Dict[Union[Type[Any], str], AnyCallable] = {}
     underscore_attrs_are_private: bool = False
 
     # whether inherited models as fields should be reconstructed as base model

pydantic/json.py

@@ -103,10 +103,7 @@ def custom_pydantic_encoder(type_encoders: Dict[Any, Callable[[Type[Any]], Any]]
         try:
             encoder = type_encoders[base]
         except KeyError:
-            try:
-                encoder = type_encoders[base.__name__]
-            except KeyError:
-                continue
+            continue
 
         return encoder(obj)
     else:  # We have exited the for loop without finding a suitable encoder

pydantic/main.py

@@ -770,14 +770,14 @@ def __try_update_forward_refs__(cls) -> None:
         Same as update_forward_refs but will not raise exception
         when forward references are not defined.
         """
-        update_model_forward_refs(cls, cls.__fields__.values(), {}, (NameError,))
+        update_model_forward_refs(cls, cls.__fields__.values(), cls.__config__.json_encoders, {}, (NameError,))
 
     @classmethod
     def update_forward_refs(cls, **localns: Any) -> None:
         """
         Try to update ForwardRefs on fields based on this Model, globalns and localns.
         """
-        update_model_forward_refs(cls, cls.__fields__.values(), localns)
+        update_model_forward_refs(cls, cls.__fields__.values(), cls.__config__.json_encoders, localns)
 
     def __iter__(self) -> 'TupleGenerator':
         """

pydantic/typing.py

@@ -461,6 +461,7 @@ def update_field_forward_refs(field: 'ModelField', globalns: Any, localns: Any)
 def update_model_forward_refs(
     model: Type[Any],
     fields: Iterable['ModelField'],
+    json_encoders: Dict[Union[Type[Any], str], AnyCallable],
     localns: 'DictStrAny',
     exc_to_suppress: Tuple[Type[BaseException], ...] = (),
 ) -> None:
@@ -480,6 +481,21 @@ def update_model_forward_refs(
         except exc_to_suppress:
             pass
 
+    for key in set(json_encoders.keys()):
+        if isinstance(key, str):
+            fr: ForwardRef = ForwardRef(key)
+        elif isinstance(key, ForwardRef):
+            fr = key
+        else:
+            continue
+
+        try:
+            new_key = evaluate_forwardref(fr, globalns, localns or None)
+        except exc_to_suppress:  # pragma: no cover
+            continue
+
+        json_encoders[new_key] = json_encoders.pop(key)
+
 
 def get_class(type_: Type[Any]) -> Union[None, bool, Type[Any]]:
     """

tests/test_forward_ref.py

@@ -626,3 +626,60 @@ class Model(BaseModel):
     )
 
     assert module.Model.__class_vars__ == {'a'}
+
+
+@skip_pre_37
+def test_json_encoder_str(create_module):
+    module = create_module(
+        # language=Python
+        """
+from pydantic import BaseModel
+
+
+class User(BaseModel):
+    x: str
+
+
+FooUser = User
+
+
+class User(BaseModel):
+    y: str
+
+
+class Model(BaseModel):
+    foo_user: FooUser
+    user: User
+
+    class Config:
+        json_encoders = {
+            'User': lambda v: f'User({v.y})',
+        }
+"""
+    )
+
+    m = module.Model(foo_user={'x': 'user1'}, user={'y': 'user2'})
+    assert m.json(models_as_dict=False) == '{"foo_user": {"x": "user1"}, "user": "User(user2)"}'
+
+
+@skip_pre_37
+def test_json_encoder_forward_ref(create_module):
+    module = create_module(
+        # language=Python
+        """
+from pydantic import BaseModel
+from typing import ForwardRef, List, Optional
+
+class User(BaseModel):
+    name: str
+    friends: Optional[List['User']] = None
+
+    class Config:
+        json_encoders = {
+            ForwardRef('User'): lambda v: f'User({v.name})',
+        }
+"""
+    )
+
+    m = module.User(name='anne', friends=[{'name': 'ben'}, {'name': 'charlie'}])
+    assert m.json(models_as_dict=False) == '{"name": "anne", "friends": ["User(ben)", "User(charlie)"]}'