♻️ Simplify internals, remove Pydantic v1 only logic, no longer needed (#14857)

tiangolo · web-flow · commit cf55bade7ea6 · 2026-02-06T19:04:24.000Z
diff --git a/fastapi/_compat/__init__.py b/fastapi/_compat/__init__.py
@@ -25,7 +25,6 @@
 from .v2 import create_body_model as create_body_model
 from .v2 import evaluate_forwardref as evaluate_forwardref
 from .v2 import get_cached_model_fields as get_cached_model_fields
-from .v2 import get_compat_model_name_map as get_compat_model_name_map
 from .v2 import get_definitions as get_definitions
 from .v2 import get_missing_field_error as get_missing_field_error
 from .v2 import get_schema_from_model_field as get_schema_from_model_field
diff --git a/fastapi/_compat/v2.py b/fastapi/_compat/v2.py
@@ -1,7 +1,7 @@
 import re
 import warnings
 from collections.abc import Sequence
-from copy import copy, deepcopy
+from copy import copy
 from dataclasses import dataclass, is_dataclass
 from enum import Enum
 from functools import lru_cache
@@ -169,11 +169,11 @@ def validate(
         values: dict[str, Any] = {},  # noqa: B006
         *,
         loc: tuple[Union[int, str], ...] = (),
-    ) -> tuple[Any, Union[list[dict[str, Any]], None]]:
+    ) -> tuple[Any, list[dict[str, Any]]]:
         try:
             return (
                 self._type_adapter.validate_python(value, from_attributes=True),
-                None,
+                [],
             )
         except ValidationError as exc:
             return None, _regenerate_error_with_loc(
@@ -305,94 +305,12 @@ def get_definitions(
         if "description" in item_def:
             item_description = cast(str, item_def["description"]).split("\f")[0]
             item_def["description"] = item_description
-    new_mapping, new_definitions = _remap_definitions_and_field_mappings(
-        model_name_map=model_name_map,
-        definitions=definitions,  # type: ignore[arg-type]
-        field_mapping=field_mapping,
-    )
-    return new_mapping, new_definitions
-
-
-def _replace_refs(
-    *,
-    schema: dict[str, Any],
-    old_name_to_new_name_map: dict[str, str],
-) -> dict[str, Any]:
-    new_schema = deepcopy(schema)
-    for key, value in new_schema.items():
-        if key == "$ref":
-            value = schema["$ref"]
-            if isinstance(value, str):
-                ref_name = schema["$ref"].split("/")[-1]
-                if ref_name in old_name_to_new_name_map:
-                    new_name = old_name_to_new_name_map[ref_name]
-                    new_schema["$ref"] = REF_TEMPLATE.format(model=new_name)
-            continue
-        if isinstance(value, dict):
-            new_schema[key] = _replace_refs(
-                schema=value,
-                old_name_to_new_name_map=old_name_to_new_name_map,
-            )
-        elif isinstance(value, list):
-            new_value = []
-            for item in value:
-                if isinstance(item, dict):
-                    new_item = _replace_refs(
-                        schema=item,
-                        old_name_to_new_name_map=old_name_to_new_name_map,
-                    )
-                    new_value.append(new_item)
-
-                else:
-                    new_value.append(item)
-            new_schema[key] = new_value
-    return new_schema
-
-
-def _remap_definitions_and_field_mappings(
-    *,
-    model_name_map: ModelNameMap,
-    definitions: dict[str, Any],
-    field_mapping: dict[
-        tuple[ModelField, Literal["validation", "serialization"]], JsonSchemaValue
-    ],
-) -> tuple[
-    dict[tuple[ModelField, Literal["validation", "serialization"]], JsonSchemaValue],
-    dict[str, Any],
-]:
-    old_name_to_new_name_map = {}
-    for field_key, schema in field_mapping.items():
-        model = field_key[0].type_
-        if model not in model_name_map or "$ref" not in schema:
-            continue
-        new_name = model_name_map[model]
-        old_name = schema["$ref"].split("/")[-1]
-        if old_name in {f"{new_name}-Input", f"{new_name}-Output"}:
-            continue
-        old_name_to_new_name_map[old_name] = new_name
-
-    new_field_mapping: dict[
-        tuple[ModelField, Literal["validation", "serialization"]], JsonSchemaValue
-    ] = {}
-    for field_key, schema in field_mapping.items():
-        new_schema = _replace_refs(
-            schema=schema,
-            old_name_to_new_name_map=old_name_to_new_name_map,
-        )
-        new_field_mapping[field_key] = new_schema
-
-    new_definitions = {}
-    for key, value in definitions.items():
-        if key in old_name_to_new_name_map:
-            new_key = old_name_to_new_name_map[key]
-        else:
-            new_key = key
-        new_value = _replace_refs(
-            schema=value,
-            old_name_to_new_name_map=old_name_to_new_name_map,
-        )
-        new_definitions[new_key] = new_value
-    return new_field_mapping, new_definitions
+    # definitions: dict[DefsRef, dict[str, Any]]
+    # but mypy complains about general str in other places that are not declared as
+    # DefsRef, although DefsRef is just str:
+    # DefsRef = NewType('DefsRef', str)
+    # So, a cast to simplify the types here
+    return field_mapping, cast(dict[str, dict[str, Any]], definitions)
 
 
 def is_scalar_field(field: ModelField) -> bool:
@@ -441,7 +359,7 @@ def serialize_sequence_value(*, field: ModelField, value: Any) -> Sequence[Any]:
     return shared.sequence_annotation_to_type[origin_type](value)  # type: ignore[no-any-return,index]
 
 
-def get_missing_field_error(loc: tuple[str, ...]) -> dict[str, Any]:
+def get_missing_field_error(loc: tuple[Union[int, str], ...]) -> dict[str, Any]:
     error = ValidationError.from_exception_data(
         "Field required", [{"type": "missing", "loc": loc, "input": {}}]
     ).errors(include_url=False)[0]
@@ -499,11 +417,6 @@ def get_model_name_map(unique_models: TypeModelSet) -> dict[TypeModelOrEnum, str
     return {v: k for k, v in name_model_map.items()}
 
 
-def get_compat_model_name_map(fields: list[ModelField]) -> ModelNameMap:
-    flat_models = get_flat_models_from_fields(fields, known_models=set())
-    return get_model_name_map(flat_models)
-
-
 def get_flat_models_from_model(
     model: type["BaseModel"], known_models: Union[TypeModelSet, None] = None
 ) -> TypeModelSet:
diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
@@ -21,7 +21,6 @@
     ModelField,
     RequiredParam,
     Undefined,
-    _regenerate_error_with_loc,
     copy_field_info,
     create_body_model,
     evaluate_forwardref,
@@ -718,12 +717,7 @@ def _validate_value_with_model_field(
             return None, [get_missing_field_error(loc=loc)]
         else:
             return deepcopy(field.default), []
-    v_, errors_ = field.validate(value, values, loc=loc)
-    if isinstance(errors_, list):
-        new_errors = _regenerate_error_with_loc(errors=errors_, loc_prefix=())
-        return None, new_errors
-    else:
-        return v_, []
+    return field.validate(value, values, loc=loc)
 
 
 def _is_json_field(field: ModelField) -> bool:
diff --git a/fastapi/openapi/utils.py b/fastapi/openapi/utils.py
@@ -9,11 +9,14 @@
 from fastapi._compat import (
     ModelField,
     Undefined,
-    get_compat_model_name_map,
     get_definitions,
     get_schema_from_model_field,
     lenient_issubclass,
 )
+from fastapi._compat.v2 import (
+    get_flat_models_from_fields,
+    get_model_name_map,
+)
 from fastapi.datastructures import DefaultPlaceholder
 from fastapi.dependencies.models import Dependant
 from fastapi.dependencies.utils import (
@@ -512,7 +515,8 @@ def get_openapi(
     webhook_paths: dict[str, dict[str, Any]] = {}
     operation_ids: set[str] = set()
     all_fields = get_fields_from_routes(list(routes or []) + list(webhooks or []))
-    model_name_map = get_compat_model_name_map(all_fields)
+    flat_models = get_flat_models_from_fields(all_fields, known_models=set())
+    model_name_map = get_model_name_map(flat_models)
     field_mapping, definitions = get_definitions(
         fields=all_fields,
         model_name_map=model_name_map,
diff --git a/fastapi/routing.py b/fastapi/routing.py
@@ -277,15 +277,12 @@ async def serialize_response(
     endpoint_ctx: Optional[EndpointContext] = None,
 ) -> Any:
     if field:
-        errors = []
         if is_coroutine:
-            value, errors_ = field.validate(response_content, {}, loc=("response",))
+            value, errors = field.validate(response_content, {}, loc=("response",))
         else:
-            value, errors_ = await run_in_threadpool(
+            value, errors = await run_in_threadpool(
                 field.validate, response_content, {}, loc=("response",)
             )
-        if isinstance(errors_, list):
-            errors.extend(errors_)
         if errors:
             ctx = endpoint_ctx or EndpointContext()
             raise ResponseValidationError(
