✅ A test `test_model_optional_union_v2` has been added to coverage the is_sequence_field function, which is involved in parsing data from FormData.

tests/test_compat.py

@@ -1,4 +1,4 @@
-from typing import List, Union
+from typing import FrozenSet, List, Optional, Set, Union
 
 from fastapi import FastAPI, UploadFile
 from fastapi._compat import (
@@ -6,6 +6,7 @@ from fastapi._compat import (
     Undefined,
     _get_model_config,
     is_bytes_sequence_annotation,
+    is_sequence_field,
     is_uploadfile_sequence_annotation,
 )
 from fastapi.testclient import TestClient
@@ -91,3 +92,24 @@ def test_is_uploadfile_sequence_annotation():
     # and other types, but I'm not even sure it's a good idea to support it as a first
     # class "feature"
     assert is_uploadfile_sequence_annotation(Union[List[str], List[UploadFile]])
+
+
+@needs_pydanticv2
+def test_model_optional_union_v2():
+    # For coverage
+    types = [
+        Optional[List[str]],
+        Union[List[int], List[float]],
+        Optional[Set[int]],
+        Union[Set[int], Set[float]],
+        Optional[FrozenSet[int]],
+        Union[List[int], None],
+    ]
+    for annotation in types:
+        field_info = FieldInfo(annotation=annotation)
+        field = ModelField(name="foo", field_info=field_info)
+        assert is_sequence_field(field) is True
+
+    field_info_str = FieldInfo(annotation=str)
+    field_str = ModelField(name="foo", field_info=field_info_str)
+    assert is_sequence_field(field_str) is False