Field: support schema_extra aliases (v2); add alias tests

fastapi · ravishan16 · Sep 25, 2025 · Sep 25, 2025 · Sep 25, 2025 · Sep 25, 2025
commit 322c6affe508855c767fcc58c2129fcd4ebc9e77
diff --git a/sqlmodel/main.py b/sqlmodel/main.py
@@ -398,6 +398,9 @@ def Field(
     schema_extra: Optional[Dict[str, Any]] = None,
 ) -> Any:
     current_schema_extra = schema_extra or {}
+    # Extract possible alias settings from schema_extra so we can control precedence
+    schema_validation_alias = current_schema_extra.pop("validation_alias", None)
+    schema_serialization_alias = current_schema_extra.pop("serialization_alias", None)
     field_info_kwargs = {
         "alias": alias,
         "title": title,
@@ -434,17 +437,25 @@ def Field(
         **current_schema_extra,
     }
     if IS_PYDANTIC_V2:
-        # Add Pydantic v2 specific parameters
-        field_info_kwargs.update(
-            {
-                "validation_alias": validation_alias,
-                "serialization_alias": serialization_alias,
-            }
+        # explicit params > schema_extra > alias propagation (handled later)
+        effective_validation_alias = (
+            validation_alias
+            if validation_alias is not None
+            else schema_validation_alias
         )
+        effective_serialization_alias = (
+            serialization_alias
+            if serialization_alias is not None
+            else schema_serialization_alias
+        )
+        if effective_validation_alias is not None:
+            field_info_kwargs["validation_alias"] = effective_validation_alias
+        if effective_serialization_alias is not None:
+            field_info_kwargs["serialization_alias"] = effective_serialization_alias
     else:
-        if validation_alias:
+        if validation_alias or schema_validation_alias is not None:
             raise RuntimeError("validation_alias is not supported in Pydantic v1")
-        if serialization_alias:
+        if serialization_alias or schema_serialization_alias is not None:
             raise RuntimeError("serialization_alias is not supported in Pydantic v1")
     field_info = FieldInfo(
         default,

diff --git a/tests/test_aliases.py b/tests/test_aliases.py
@@ -5,7 +5,7 @@
 from pydantic import Field as PField
 from sqlmodel import Field, SQLModel
 
-from tests.conftest import needs_pydanticv2
+from tests.conftest import needs_pydanticv1, needs_pydanticv2
 
 """
 Alias tests for SQLModel and Pydantic compatibility
@@ -21,8 +21,6 @@ class SQLModelUser(SQLModel):
 
 
 # Models with config (validate_by_name=True)
-
-
 if VERSION.startswith("2."):
 
     class PydanticUserWithConfig(PydanticUser):
@@ -138,18 +136,16 @@ class SQLModelUserV2(SQLModel):
     SQLModelUserV2 = None
 
 
+@needs_pydanticv1
 def test_validation_alias_runtimeerror_pydantic_v1():
-    if VERSION.startswith("2."):
-        pytest.skip("Only relevant for Pydantic v1")
     with pytest.raises(
         RuntimeError, match="validation_alias is not supported in Pydantic v1"
     ):
         Field(validation_alias="foo")
 
 
+@needs_pydanticv1
 def test_serialization_alias_runtimeerror_pydantic_v1():
-    if VERSION.startswith("2."):
-        pytest.skip("Only relevant for Pydantic v1")
     with pytest.raises(
         RuntimeError, match="serialization_alias is not supported in Pydantic v1"
     ):
@@ -176,3 +172,85 @@ def test_serialize_with_serialization_alias(
     assert "firstName" not in data
     assert "first_name" not in data
     assert data["f_name"] == "Jane"
+
+
+@needs_pydanticv2
+def test_schema_extra_validation_alias_sqlmodel_v2():
+    class M(SQLModel):
+        f: str = Field(schema_extra={"validation_alias": "f_alias"})
+
+    m = M.model_validate({"f_alias": "asd"})
+    assert m.f == "asd"
+
+
+@needs_pydanticv2
+def test_schema_extra_serialization_alias_sqlmodel_v2():
+    class M(SQLModel):
+        f: str = Field(schema_extra={"serialization_alias": "f_out"})
+
+    m = M(f="x")
+    data = m.model_dump(by_alias=True)
+    assert "f_out" in data
+    assert "f" not in data
+    assert data["f_out"] == "x"
+
+
+@needs_pydanticv1
+def test_schema_extra_validation_alias_runtimeerror_pydantic_v1():
+    with pytest.raises(
+        RuntimeError, match="validation_alias is not supported in Pydantic v1"
+    ):
+        Field(schema_extra={"validation_alias": "x"})
+
+
+@needs_pydanticv1
+def test_schema_extra_serialization_alias_runtimeerror_pydantic_v1():
+    with pytest.raises(
+        RuntimeError, match="serialization_alias is not supported in Pydantic v1"
+    ):
+        Field(schema_extra={"serialization_alias": "y"})
+
+
+@needs_pydanticv2
+def test_alias_plus_validation_alias_prefers_validation_alias_sqlmodel_v2():
+    class M(SQLModel):
+        first_name: str = Field(alias="fullName", validation_alias="v_name")
+
+    m = M.model_validate({"fullName": "A", "v_name": "B"})
+    assert m.first_name == "B"
+
+
+@needs_pydanticv2
+def test_alias_plus_serialization_alias_prefers_serialization_alias_sqlmodel_v2():
+    class M(SQLModel):
+        first_name: str = Field(alias="fullName", serialization_alias="f_name")
+
+    m = M(first_name="Z")
+    data = m.model_dump(by_alias=True)
+    assert "f_name" in data
+    assert "fullName" not in data
+    assert data["f_name"] == "Z"
+
+
+@needs_pydanticv2
+def test_alias_generator_works_sqlmodel_v2():
+    class M(SQLModel):
+        model_config = {"alias_generator": lambda s: "gen_" + s}
+        f: str = Field()
+
+    m = M.model_validate({"gen_f": "ok"})
+    assert m.f == "ok"
+    data = m.model_dump(by_alias=True)
+    assert "gen_f" in data and data["gen_f"] == "ok"
+
+
+@needs_pydanticv2
+def test_alias_generator_with_explicit_alias_prefers_field_alias_sqlmodel_v2():
+    class M(SQLModel):
+        model_config = {"alias_generator": lambda s: "gen_" + s}
+        f: str = Field(alias="custom")
+
+    m = M.model_validate({"custom": "ok"})
+    assert m.f == "ok"
+    data = m.model_dump(by_alias=True)
+    assert "custom" in data and "gen_f" not in data