From d1ac537285817664b1260597e10d372d7a329152 Mon Sep 17 00:00:00 2001
From: Nico Tonnhofer <github@wurstnase.de>
Date: Thu, 25 Sep 2025 12:18:54 +0200
Subject: [PATCH] Fix handle alias for query in pydantic model

---
 fastapi/dependencies/utils.py    |  2 +-
 tests/test_query_single_model.py | 83 ++++++++++++++++++++++++++++++++
 2 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 tests/test_query_single_model.py

diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
index e49380cb3..45962fcba 100644
--- a/fastapi/dependencies/utils.py
+++ b/fastapi/dependencies/utils.py
@@ -788,7 +788,7 @@ def request_params_to_args(
                 )
         value = _get_multidict_value(field, received_params, alias=alias)
         if value is not None:
-            params_to_process[field.name] = value
+            params_to_process[field.alias] = value
         processed_keys.add(alias or field.alias)
         processed_keys.add(field.name)
 
diff --git a/tests/test_query_single_model.py b/tests/test_query_single_model.py
new file mode 100644
index 000000000..f4379c4ec
--- /dev/null
+++ b/tests/test_query_single_model.py
@@ -0,0 +1,83 @@
+from typing import List, Optional
+
+from dirty_equals import IsDict
+from fastapi import FastAPI, Query
+from fastapi.testclient import TestClient
+from pydantic import BaseModel, Field
+from typing_extensions import Annotated
+
+app = FastAPI()
+
+
+class QueryModel(BaseModel):
+    item: List[int] = []
+    with_alias: Optional[str] = Field(alias="withAlias", default=None)
+    without_alias: str = "default"
+
+
+@app.get("/query")
+def get_query(query: Annotated[QueryModel, Query()]):
+    return query
+
+
+client = TestClient(app)
+
+
+def test_query():
+    response = client.get(
+        "/query",
+        params={
+            "item": [1, 2],
+            "withAlias": "abc123",
+            "without_alias": "custom",
+        },
+    )
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "item": [1, 2],
+        "withAlias": "abc123",
+        "without_alias": "custom",
+    }
+
+
+def test_defaults():
+    response = client.get("/query", params={"item": [1, 2]})
+    assert response.status_code == 200, response.text
+    assert response.json() == {
+        "item": [1, 2],
+        "withAlias": None,
+        "without_alias": "default",
+    }
+
+
+def test_invalid_data():
+    response = client.get(
+        "/query",
+        params={
+            "item": ["invalid"],
+        },
+    )
+    assert response.status_code == 422, response.text
+    assert response.json() == IsDict(
+        {
+            "detail": [
+                {
+                    "type": "int_parsing",
+                    "loc": ["query", "item", 0],
+                    "msg": "Input should be a valid integer, unable to parse string as an integer",
+                    "input": "invalid",
+                }
+            ]
+        }
+    ) | IsDict(
+        # TODO: remove when deprecating Pydantic v1
+        {
+            "detail": [
+                {
+                    "loc": ["query", "item", 0],
+                    "msg": "Input should be a valid integer, unable to parse string as an integer",
+                    "type": "type_error.int_parsing",
+                }
+            ]
+        }
+    )