fix: allow submodels to overwrite extra field info (#3935)

* fix: allow submodels to overwrite extra field info

* fix(deps): pin jinja2 for mkdocs

changes/3934-PrettyWood.md

@@ -0,0 +1 @@
+allow submodels to overwrite extra field info

pydantic/fields.py

@@ -201,7 +201,8 @@ def update_from_config(self, from_config: Dict[str, Any]) -> None:
                 current_value = getattr(self, attr_name)
             except AttributeError:
                 # attr_name is not an attribute of FieldInfo, it should therefore be added to extra
-                self.extra[attr_name] = value
+                # (except if extra already has this value!)
+                self.extra.setdefault(attr_name, value)
             else:
                 if current_value is self.__field_constraints__.get(attr_name, None):
                     setattr(self, attr_name, value)

tests/test_schema.py

@@ -3001,3 +3001,27 @@ class Model(BaseModel):
             },
         },
     }
+
+
+def test_extra_inheritance():
+    class A(BaseModel):
+        root: Optional[str]
+
+        class Config:
+            fields = {
+                'root': {'description': 'root path of data', 'level': 1},
+            }
+
+    class Model(A):
+        root: str = Field('asa', description='image height', level=3)
+
+    m = Model()
+    assert m.schema()['properties'] == {
+        'root': {
+            'title': 'Root',
+            'type': 'string',
+            'description': 'image height',
+            'default': 'asa',
+            'level': 3,
+        }
+    }