From a36c655c4393fd43b755f66f98d7c32ec5d3c896 Mon Sep 17 00:00:00 2001
From: adhoc <postma.marin@protonmail.com>
Date: Tue, 25 Mar 2025 14:50:20 +0100
Subject: [PATCH 1/4] fix none default

---
 fastapi/dependencies/utils.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fastapi/dependencies/utils.py b/fastapi/dependencies/utils.py
index d205d17fa..43e74452b 100644
--- a/fastapi/dependencies/utils.py
+++ b/fastapi/dependencies/utils.py
@@ -837,6 +837,7 @@ async def _extract_form_body(
     values = {}
     first_field = body_fields[0]
     first_field_info = first_field.field_info
+    processed_keys = set()
 
     for field in body_fields:
         value = _get_multidict_value(field, received_body)
@@ -865,10 +866,11 @@ async def _extract_form_body(
                 for sub_value in value:
                     tg.start_soon(process_fn, sub_value.read)
             value = serialize_sequence_value(field=field, value=results)
+        processed_keys.add(field.alias)
         if value is not None:
             values[field.alias] = value
     for key, value in received_body.items():
-        if key not in values:
+        if key not in processed_keys:
             values[key] = value
     return values
 

From 5e501bb4c00ca0032da0a42fa40f5bafeb6c4c6a Mon Sep 17 00:00:00 2001
From: adhoc <postma.marin@protonmail.com>
Date: Tue, 25 Mar 2025 15:38:04 +0100
Subject: [PATCH 2/4] add tests

---
 tests/test_form_default.py | 46 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 tests/test_form_default.py

diff --git a/tests/test_form_default.py b/tests/test_form_default.py
new file mode 100644
index 000000000..1c42bb401
--- /dev/null
+++ b/tests/test_form_default.py
@@ -0,0 +1,46 @@
+from typing import Annotated, Optional
+
+from fastapi import FastAPI, File, Form
+from starlette.testclient import TestClient
+
+app = FastAPI()
+client = TestClient(app)
+
+
+@app.post("/urlencoded")
+async def post_url_encoded(age: Annotated[Optional[int], Form()] = None):
+    return age
+
+
+def test_form_default_url_encoded():
+    response = client.post("/urlencoded", data={"age": ""})
+    assert response.status_code == 200
+    assert response.text == "null"
+
+
+@app.post("/multipart")
+async def post_multi_part(
+    age: Annotated[Optional[int], Form()] = None,
+    file: Annotated[Optional[bytes], File()] = None,
+):
+    assert file is None
+    assert age is None
+
+
+def test_form_default_multi_part():
+    response = client.post("/multipart", data={"age": ""})
+    assert response.status_code == 200
+
+
+@app.post("/multipart-file-first")
+async def post_multi_part_file_first(
+    file: Annotated[Optional[bytes], File()] = None,
+    age: Annotated[Optional[int], Form()] = None,
+):
+    assert file is None
+    assert age is None
+
+
+def test_form_default_multi_part_file_first():
+    response = client.post("/multipart-file-first", data={"age": ""})
+    assert response.status_code == 200

From f2648fe45c9ca137fcee008dc3ddc0c521fcbf92 Mon Sep 17 00:00:00 2001
From: adhoc <postma.marin@protonmail.com>
Date: Tue, 25 Mar 2025 16:17:47 +0100
Subject: [PATCH 3/4] fix import

---
 tests/test_form_default.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_form_default.py b/tests/test_form_default.py
index 1c42bb401..f31c92ecf 100644
--- a/tests/test_form_default.py
+++ b/tests/test_form_default.py
@@ -1,4 +1,4 @@
-from typing import Annotated, Optional
+from typing_extensions import Annotated, Optional
 
 from fastapi import FastAPI, File, Form
 from starlette.testclient import TestClient

From da43c9c91ac9badc425d780697a771b5b8a9a0eb Mon Sep 17 00:00:00 2001
From: "pre-commit-ci[bot]"
 <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Date: Tue, 25 Mar 2025 15:18:01 +0000
Subject: [PATCH 4/4] =?UTF-8?q?=F0=9F=8E=A8=20[pre-commit.ci]=20Auto=20for?=
 =?UTF-8?q?mat=20from=20pre-commit.com=20hooks?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 tests/test_form_default.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/test_form_default.py b/tests/test_form_default.py
index f31c92ecf..97ff47463 100644
--- a/tests/test_form_default.py
+++ b/tests/test_form_default.py
@@ -1,7 +1,8 @@
-from typing_extensions import Annotated, Optional
+from typing import Optional
 
 from fastapi import FastAPI, File, Form
 from starlette.testclient import TestClient
+from typing_extensions import Annotated
 
 app = FastAPI()
 client = TestClient(app)