Add tests and fix handling of multiple fields

fastapi/dependencies/utils.py

@@ -750,30 +750,34 @@ def request_params_to_args(
     if not fields:
         return values, errors
 
-    first_field = fields[0]
-    fields_to_extract = fields
-    single_not_embedded_field = False
-    default_convert_underscores = True
-    if len(fields) == 1 and lenient_issubclass(first_field.type_, BaseModel):
-        fields_to_extract = get_cached_model_fields(first_field.type_)
-        single_not_embedded_field = True
-        # If headers are in a Pydantic model, the way to disable convert_underscores
-        # would be with Header(convert_underscores=False) at the Pydantic model level
-        default_convert_underscores = getattr(
-            first_field.field_info, "convert_underscores", True
-        )
+    fields_to_extract = []
+    for field in fields:
+        if lenient_issubclass(field.type_, BaseModel):
+            fields_to_extract.extend(
+                [
+                    (model_field, field)
+                    for model_field in get_cached_model_fields(field.type_)
+                ]
+            )
+        else:
+            fields_to_extract.append((field, field))
 
     params_to_process: Dict[str, Any] = {}
 
     processed_keys = set()
 
-    for field in fields_to_extract:
+    for field, base_field in fields_to_extract:
         alias = None
         if isinstance(received_params, Headers):
             # Handle fields extracted from a Pydantic Model for a header, each field
             # doesn't have a FieldInfo of type Header with the default convert_underscores=True
+
+            # If headers are in a Pydantic model, the way to disable convert_underscores
+            # would be with Header(convert_underscores=False) at the Pydantic model level
             convert_underscores = getattr(
-                field.field_info, "convert_underscores", default_convert_underscores
+                field.field_info, 
+                "convert_underscores", 
+                getattr(base_field.field_info, "convert_underscores", True)
             )
             if convert_underscores:
                 alias = (
@@ -791,24 +795,18 @@ def request_params_to_args(
         if key not in processed_keys:
             params_to_process[key] = value
 
-    if single_not_embedded_field:
-        field_info = first_field.field_info
-        assert isinstance(field_info, params.Param), (
-            "Params must be subclasses of Param"
-        )
-        loc: Tuple[str, ...] = (field_info.in_.value,)
-        v_, errors_ = _validate_value_with_model_field(
-            field=first_field, value=params_to_process, values=values, loc=loc
-        )
-        return {first_field.name: v_}, errors_
-
     for field in fields:
-        value = _get_multidict_value(field, received_params)
         field_info = field.field_info
-        assert isinstance(field_info, params.Param), (
-            "Params must be subclasses of Param"
-        )
-        loc = (field_info.in_.value, field.alias)
+        assert isinstance(
+            field_info, params.Param
+        ), "Params must be subclasses of Param"
+
+        if lenient_issubclass(field.type_, BaseModel):
+            value = params_to_process
+            loc: tuple[str, ...] = (field_info.in_.value,)
+        else:
+            value = _get_multidict_value(field, received_params)
+            loc = (field_info.in_.value, field.alias)
         v_, errors_ = _validate_value_with_model_field(
             field=field, value=value, values=values, loc=loc
         )

tests/test_multiple_parameter_models.py

@@ -0,0 +1,106 @@
+import pytest
+from fastapi import Cookie, Depends, FastAPI, Header, Query
+from fastapi.testclient import TestClient
+from pydantic import BaseModel, Field
+
+app = FastAPI()
+
+
+class Model(BaseModel):
+    field1: int = Field(0)
+
+
+class Model2(BaseModel):
+    field2: int = Field(0)
+
+
+for param in (Query, Header, Cookie):
+
+    def dependency(field2: int = param(0)):
+        return field2
+
+    @app.get(f"/{param.__name__.lower()}-depends/")
+    async def with_depends(model1: Model = param(), dependency=Depends(dependency)):
+        return {"field1": model1.field1, "field2": dependency}
+
+    @app.get(f"/{param.__name__.lower()}-argument/")
+    async def with_model_and_argument(model1: Model = param(), field2: int = param(0)):
+        return {"field1": model1.field1, "field2": field2}
+
+    @app.get(f"/{param.__name__.lower()}-models/")
+    async def with_models(model1: Model = param(), model2: Model2 = param()):
+        return {"field1": model1.field1, "field2": model2.field2}
+
+    @app.get(f"/{param.__name__.lower()}-arguments/")
+    async def with_argument(field1: int = param(0), field2: int = param(0)):
+        return {"field1": field1, "field2": field2}
+
+
+client = TestClient(app)
+
+
+@pytest.mark.parametrize(
+    "path",
+    ["/query-depends/", "/query-arguments/", "/query-argument/", "/query-models/"],
+)
+def test_query_depends(path):
+    response = client.get(path, params={"field1": 0, "field2": 1})
+    assert response.status_code == 200
+    assert response.json() == {"field1": 0, "field2": 1}
+
+
+@pytest.mark.parametrize(
+    "path",
+    ["/header-depends/", "/header-arguments/", "/header-argument/", "/header-models/"],
+)
+def test_header_depends(path):
+    response = client.get(path, headers={"field1": "0", "field2": "1"})
+    assert response.status_code == 200
+    assert response.json() == {"field1": 0, "field2": 1}
+
+
+@pytest.mark.parametrize(
+    "path",
+    ["/cookie-depends/", "/cookie-arguments/", "/cookie-argument/", "/cookie-models/"],
+)
+def test_cookie_depends(path):
+    client.cookies = {"field1": "0", "field2": "1"}
+    response = client.get(path)
+    assert response.status_code == 200
+    assert response.json() == {"field1": 0, "field2": 1}
+
+
+@pytest.mark.parametrize(
+    ("path", "in_"),
+    [
+        ("/query-depends/", "query"),
+        ("/query-arguments/", "query"),
+        ("/query-argument/", "query"),
+        ("/query-models/", "query"),
+        ("/header-depends/", "header"),
+        ("/header-arguments/", "header"),
+        ("/header-argument/", "header"),
+        ("/header-models/", "header"),
+        ("/cookie-depends/", "cookie"),
+        ("/cookie-arguments/", "cookie"),
+        ("/cookie-argument/", "cookie"),
+        ("/cookie-models/", "cookie"),
+    ],
+)
+def test_parameters_openapi_schema(path, in_):
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json()["paths"][path]["get"]["parameters"] == [
+        {
+            "name": "field1",
+            "in": in_,
+            "required": False,
+            "schema": {"type": "integer", "default": 0, "title": "Field1"},
+        },
+        {
+            "name": "field2",
+            "in": in_,
+            "required": False,
+            "schema": {"type": "integer", "default": 0, "title": "Field2"},
+        },
+    ]