Preserve RootModel core metadata

Viicos · Viicos · commit 8522ebb71e5e · 2026-05-06T10:06:42.000+02:00
Backport of: #13129
diff --git a/pydantic/_internal/_generate_schema.py b/pydantic/_internal/_generate_schema.py
@@ -840,8 +840,17 @@ def _model_schema(self, cls: type[BaseModel]) -> core_schema.CoreSchema:
                 generic_origin: type[BaseModel] | None = getattr(cls, '__pydantic_generic_metadata__', {}).get('origin')
 
                 if cls.__pydantic_root_model__:
-                    # FIXME: should the common field metadata be used here?
-                    inner_schema, _ = self._common_field_schema('root', fields['root'], decorators)
+                    inner_schema, metadata = self._common_field_schema('root', fields['root'], decorators)
+                    if cls.__doc__ and metadata.get('pydantic_js_updates', {}).get('description'):
+                        # This is a bit of a leaky abstraction, but as the model docstring takes priority
+                        # over the root field's description, we need to override it here. This can't be done
+                        # in the JSON Schema generation logic because the metadata's `pydantic_js_updates` are
+                        # applied last, and overrides any value previously set (so the description set from the
+                        # docstring in `GenerateJsonSchema._update_class_schema()` is overridden):
+                        update_core_metadata(
+                            metadata, pydantic_js_updates={'description': inspect.cleandoc(cls.__doc__)}
+                        )
+
                     inner_schema = apply_model_validators(inner_schema, model_validators, 'inner')
                     model_schema = core_schema.model_schema(
                         cls,
@@ -852,6 +861,7 @@ def _model_schema(self, cls: type[BaseModel]) -> core_schema.CoreSchema:
                         post_init=getattr(cls, '__pydantic_post_init__', None),
                         config=core_config,
                         ref=model_ref,
+                        metadata=metadata,
                     )
                 else:
                     fields_schema: core_schema.CoreSchema = core_schema.model_fields_schema(
diff --git a/pydantic/json_schema.py b/pydantic/json_schema.py
@@ -1636,7 +1636,6 @@ def _update_class_schema(self, json_schema: JsonSchemaValue, cls: type[Any], con
         """
         from ._internal._dataclasses import is_stdlib_dataclass
         from .main import BaseModel
-        from .root_model import RootModel
 
         if (config_title := config.get('title')) is not None:
             json_schema.setdefault('title', config_title)
@@ -1664,8 +1663,6 @@ def _update_class_schema(self, json_schema: JsonSchemaValue, cls: type[Any], con
 
         if docstring:
             json_schema.setdefault('description', inspect.cleandoc(docstring))
-        elif issubclass(cls, RootModel) and (root_description := cls.__pydantic_fields__['root'].description):
-            json_schema.setdefault('description', root_description)
 
         extra = config.get('extra')
         if 'additionalProperties' not in json_schema:  # This check is particularly important for `typed_dict_schema()`
diff --git a/tests/test_json_schema.py b/tests/test_json_schema.py
@@ -5391,6 +5391,38 @@ class C(RootModel[A]):
     }
 
 
+def test_root_model_annotated_root_type_parameterized() -> None:
+    """https://github.com/pydantic/pydantic/issues/13123"""
+
+    MyType = Annotated[str, Field(examples=['hello'], description='desc', deprecated=True)]
+
+    class MyModel(RootModel[MyType]):
+        pass
+
+    assert MyModel.model_json_schema() == {
+        'deprecated': True,
+        'description': 'desc',
+        'examples': ['hello'],
+        'title': 'MyModel',
+        'type': 'string',
+    }
+
+
+def test_root_model_annotated_root_type() -> None:
+    """https://github.com/pydantic/pydantic/issues/13123"""
+
+    class MyModel(RootModel):
+        root: Annotated[str, Field(examples=['hello'], description='desc', deprecated=True)]
+
+    assert MyModel.model_json_schema() == {
+        'deprecated': True,
+        'description': 'desc',
+        'examples': ['hello'],
+        'title': 'MyModel',
+        'type': 'string',
+    }
+
+
 def test_type_adapter_json_schemas_title_description():
     class Model(BaseModel):
         a: str
