right directions maybe

docs_src/query_params/tutorial007_py310.py

@@ -1,6 +1,7 @@
 from typing import Annotated, Dict, List, Union
 
 from fastapi import FastAPI, Query
+from pydantic import OnErrorOmit
 
 app = FastAPI()
 
@@ -9,7 +10,7 @@ app = FastAPI()
 def get_mixed_mapping_mixed_type_query_params(
     query: Annotated[int, Query()] = None,
     mapping_query_str_or_int: Annotated[
-        Union[Dict[str, str], Dict[str, int]], Query()
+        Union[Dict[str, OnErrorOmit[str]], Dict[str, int]], Query()
     ] = None,
     mapping_query_int: Annotated[Dict[str, int], Query()] = None,
     sequence_mapping_int: Annotated[Dict[str, List[int]], Query()] = None,

fastapi/_compat/__init__.py

@@ -21,7 +21,6 @@ from .main import get_compat_model_name_map as get_compat_model_name_map
 from .main import get_definitions as get_definitions
 from .main import get_missing_field_error as get_missing_field_error
 from .main import get_schema_from_model_field as get_schema_from_model_field
-from .main import ignore_invalid as ignore_invalid
 from .main import is_bytes_field as is_bytes_field
 from .main import is_bytes_sequence_field as is_bytes_sequence_field
 from .main import is_scalar_field as is_scalar_field
@@ -29,6 +28,7 @@ from .main import is_scalar_mapping_field as is_scalar_mapping_field
 from .main import is_scalar_sequence_field as is_scalar_sequence_field
 from .main import is_scalar_sequence_mapping_field as is_scalar_sequence_mapping_field
 from .main import is_sequence_field as is_sequence_field
+from .main import omit_by_default as omit_by_default
 from .main import serialize_sequence_value as serialize_sequence_value
 from .main import (
     with_info_plain_validator_function as with_info_plain_validator_function,
@@ -42,6 +42,9 @@ from .shared import PYDANTIC_V2 as PYDANTIC_V2
 from .shared import PYDANTIC_VERSION_MINOR_TUPLE as PYDANTIC_VERSION_MINOR_TUPLE
 from .shared import annotation_is_pydantic_v1 as annotation_is_pydantic_v1
 from .shared import field_annotation_is_scalar as field_annotation_is_scalar
+from .shared import (
+    field_annotation_is_scalar_sequence_mapping as field_annotation_is_scalar_sequence_mapping,
+)
 from .shared import (
     is_uploadfile_or_nonable_uploadfile_annotation as is_uploadfile_or_nonable_uploadfile_annotation,
 )

fastapi/_compat/main.py

@@ -28,6 +28,7 @@ if PYDANTIC_V2:
     from .v2 import Validator as Validator
     from .v2 import evaluate_forwardref as evaluate_forwardref
     from .v2 import get_missing_field_error as get_missing_field_error
+    from .v2 import omit_by_default as omit_by_default
     from .v2 import (
         with_info_plain_validator_function as with_info_plain_validator_function,
     )

fastapi/_compat/shared.py

@@ -5,7 +5,6 @@ from collections import deque
 from dataclasses import is_dataclass
 from typing import (
     Any,
-    Callable,
     Deque,
     FrozenSet,
     List,
@@ -19,7 +18,7 @@ from typing import (
 
 from fastapi._compat import may_v1
 from fastapi.types import UnionType
-from pydantic import BaseModel, ValidationError
+from pydantic import BaseModel
 from pydantic.version import VERSION as PYDANTIC_VERSION
 from starlette.datastructures import UploadFile
 from typing_extensions import Annotated, get_args, get_origin

fastapi/_compat/v1.py

@@ -348,4 +348,3 @@ def create_body_model(
 
 def get_model_fields(model: Type[BaseModel]) -> List[ModelField]:
     return list(model.__fields__.values())  # type: ignore[attr-defined]
-

fastapi/_compat/v2.py

@@ -17,8 +17,8 @@ from typing import (
 
 from fastapi._compat import may_v1, shared
 from fastapi.openapi.constants import REF_TEMPLATE
-from fastapi.types import IncEx, ModelNameMap
+from fastapi.types import IncEx, ModelNameMap, UnionType
-from pydantic import BaseModel, TypeAdapter, WrapValidator, create_model
+from pydantic import BaseModel, OnErrorOmit, TypeAdapter, create_model
 from pydantic import PydanticSchemaGenerationError as PydanticSchemaGenerationError
 from pydantic import PydanticUndefinedAnnotation as PydanticUndefinedAnnotation
 from pydantic import ValidationError as ValidationError
@@ -488,3 +488,21 @@ def get_flat_models_from_fields(
 def get_long_model_name(model: TypeModelOrEnum) -> str:
     return f"{model.__module__}__{model.__qualname__}".replace(".", "__")
 
+
+def omit_by_default(annotation: Any) -> Any:
+    # Update the annotation to use OnErrorOmit for the inner type(s)
+    origin = get_origin(annotation)
+    if origin is Union or origin is UnionType:
+        new_args = []
+        for arg in get_args(annotation):
+            new_arg = omit_by_default(arg)
+            new_args.append(new_arg)
+        return Union[tuple(new_args)]  # type: ignore[return-value]
+    elif origin is Annotated:
+        annotated_args = get_args(annotation)
+        base_annotation = annotated_args[0]
+        new_base_annotation = omit_by_default(base_annotation)
+        new_metadata = annotated_args[1:]
+        return Annotated[new_base_annotation + new_metadata]  # type: ignore[return-value]
+    else:
+        return OnErrorOmit[annotation]  # type: ignore[return-value]

fastapi/dependencies/utils.py

@@ -31,6 +31,7 @@ from fastapi._compat import (
     create_body_model,
     evaluate_forwardref,
     field_annotation_is_scalar,
+    field_annotation_is_scalar_sequence_mapping,
     get_annotation_from_field_info,
     get_cached_model_fields,
     get_missing_field_error,
@@ -45,6 +46,7 @@ from fastapi._compat import (
     is_uploadfile_sequence_annotation,
     lenient_issubclass,
     may_v1,
+    omit_by_default,
     sequence_types,
     serialize_sequence_value,
     value_is_sequence,
@@ -63,7 +65,7 @@ from fastapi.security.oauth2 import OAuth2, SecurityScopes
 from fastapi.security.open_id_connect_url import OpenIdConnect
 from fastapi.types import DependencyCacheKey
 from fastapi.utils import create_model_field, get_path_param_names
-from pydantic import BaseModel, TypeAdapter
+from pydantic import BaseModel
 from pydantic.fields import FieldInfo
 from starlette.background import BackgroundTasks as StarletteBackgroundTasks
 from starlette.concurrency import run_in_threadpool
@@ -485,6 +487,12 @@ def analyze_param(
             and getattr(field_info, "in_", None) is None
         ):
             field_info.in_ = params.ParamTypes.query
+
+        if isinstance(
+            field_info, (params.Query, temp_pydantic_v1_params.Query)
+        ) and field_annotation_is_scalar_sequence_mapping(use_annotation):
+            use_annotation = omit_by_default(use_annotation)
+
         use_annotation_from_field_info = get_annotation_from_field_info(
             use_annotation,
             field_info,
@@ -523,10 +531,6 @@ def analyze_param(
                     and getattr(field, "shape", 1) == 1
                 )
             )
-            if is_scalar_sequence_field(field) or is_scalar_sequence_mapping_field(
-                field
-            ):
-                field._type_adapter.core_schema["on_error"] = "omit"
 
     return ParamDetails(type_annotation=type_annotation, depends=depends, field=field)
 

fastapi/params.py

@@ -305,6 +305,7 @@ class Query(Param):  # type: ignore[misc]
             json_schema_extra=json_schema_extra,
             **extra,
         )
+        self.annotation = self.annotation
 
 
 class Header(Param):  # type: ignore[misc]

tests/test_tutorial/test_query_params/test_tutorial007_py310.py

@@ -17,7 +17,7 @@ def test_foo_needy_very(client: TestClient):
         "query": 2,
         "mapping_query_str_or_int": {"foo": "baz"},
         "mapping_query_int": {},
-        "sequence_mapping_int": {},
+        "sequence_mapping_int": {"foo": []},
     }