Allow passing json_encoders in class kwargs (#2523)

* Test that `json_encoders` are respected from class kwargs

* Allow passing `json_encoders` in class kwargs

Fixes #2521.

changes/2521-layday.md

@@ -0,0 +1 @@
+Allow passing `json_encoders` in class kwargs

pydantic/main.py

@@ -184,6 +184,7 @@ def inherit_config(self_config: 'ConfigType', parent_config: 'ConfigType', **nam
     namespace['json_encoders'] = {
         **getattr(parent_config, 'json_encoders', {}),
         **getattr(self_config, 'json_encoders', {}),
+        **namespace.get('json_encoders', {}),
     }
 
     return type('Config', base_classes, namespace)

tests/test_main.py

@@ -1997,6 +1997,13 @@ def test_class_kwargs_config():
     assert Model.__fields__['b'].alias == 'B'  # alias_generator still works
 
 
+def test_class_kwargs_config_json_encoders():
+    class Model(BaseModel, json_encoders={int: str}):
+        pass
+
+    assert Model.__config__.json_encoders == {int: str}
+
+
 def test_class_kwargs_config_and_attr_conflict():
 
     with pytest.raises(