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🐛 Fix alias support for Pydantic v2 #1577

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🐛 Fix alias support for Pydantic v2 #1577

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785270a
feat: Add support for Pydantic v2 aliases
ravishan16 Sep 25, 2025
72e8c36
fix: Skip alias tests in Pydantic v1
ravishan16 Sep 25, 2025
15c7954
feat: Add support for Pydantic v2 aliases
ravishan16 Sep 25, 2025
3cc2b1e
fix: Skip alias tests in Pydantic v1
ravishan16 Sep 25, 2025
34d2a45
fix: Add Pydantic v2 alias support with backward compatibility
ravishan16 Sep 25, 2025
6667109
Apply suggestion from @YuriiMotov
ravishan16 Sep 30, 2025
382a52d
fix: move this outside of if..else.. block to avoid duplicati as per …
ravishan16 Sep 30, 2025
d3e761e
fix: Addressed yurii's comments
ravishan16 Sep 30, 2025
e3dbf75
Merge branch 'fastapi:main' into issue-1536-alias-pydantic-v2
ravishan16 Oct 8, 2025
e07a259
Update tests/test_aliases.py
ravishan16 Oct 8, 2025
6b7a0a1
🎨 [pre-commit.ci] Auto format from pre-commit.com hooks
pre-commit-ci[bot] Oct 8, 2025
322c6af
Field: support schema_extra aliases (v2); add alias tests
ravishan16 Oct 9, 2025
6b13381
Field: support schema_extra aliases (v2); add alias tests
ravishan16 Oct 9, 2025
7b2bc2c
compat: drop redundant v2 check in post_init_field_info;
ravishan16 Oct 9, 2025
68b31d7
Simplify alias propagation logic for Pydantic v2
YuriiMotov Oct 9, 2025
9440956
Fix test name and avoid deprecation warnings
YuriiMotov Oct 9, 2025
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fix: Addressed yurii's comments
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@ravishan16
ravishan16 committed Sep 30, 2025
commit d3e761ebc5c965d39c60b7510264c83e29d6d422
69 changes: 37 additions & 32 deletions tests/test_aliases.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,8 +5,11 @@
from pydantic import Field as PField
from sqlmodel import Field, SQLModel

# -----------------------------------------------------------------------------------
# Models
from tests.conftest import needs_pydanticv2

"""
Alias tests for SQLModel and Pydantic compatibility
"""


class PydanticUser(BaseModel):
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@YuriiMotov YuriiMotov Sep 30, 2025

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We should think whether we want to keep parameterizing tests with Pydantic models.
Initially I parametrized tests with both, Pydantic and SQLModel models to show the difference in behavior between SQLModel and Pydantic models.

If it's useful to keep this parametrization in repo? 🤔
Tests would be a bit simpler without it, but on the other hand this way we ensure it works the same as with Pydantic model

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@ravishan16 ravishan16 Sep 30, 2025

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Personally, I think it’s useful to keep the parametrization for now, since it acts as a kind of integration test between the two libraries.

Expand Down Expand Up @@ -39,12 +42,6 @@ class Config:
allow_population_by_field_name = True


# -----------------------------------------------------------------------------------
# Tests

# Test validate by name


@pytest.mark.parametrize("model", [PydanticUser, SQLModelUser])
def test_create_with_field_name(model: Union[Type[PydanticUser], Type[SQLModelUser]]):
with pytest.raises(ValidationError):
Expand All @@ -59,9 +56,6 @@ def test_create_with_field_name_with_config(
assert user.full_name == "Alice"


# Test validate by alias


@pytest.mark.parametrize(
"model",
[PydanticUser, SQLModelUser, PydanticUserWithConfig, SQLModelUserWithConfig],
Expand All @@ -78,9 +72,6 @@ def test_create_with_alias(
assert user.full_name == "Bob"


# Test validate by name and alias


@pytest.mark.parametrize("model", [PydanticUserWithConfig, SQLModelUserWithConfig])
def test_create_with_both_prefers_alias(
model: Union[Type[PydanticUserWithConfig], Type[SQLModelUserWithConfig]],
Expand All @@ -89,48 +80,47 @@ def test_create_with_both_prefers_alias(
assert user.full_name == "Charlie" # alias should take precedence


# Test serialize


@pytest.mark.parametrize("model", [PydanticUser, SQLModelUser])
def test_dict_default_uses_field_names(
model: Union[Type[PydanticUser], Type[SQLModelUser]],
):
user = model(fullName="Dana")
data = user.dict()
if VERSION.startswith("2."):
data = user.model_dump()
else:
data = user.dict()
assert "full_name" in data
assert "fullName" not in data
assert data["full_name"] == "Dana"


# Test serialize by alias


@pytest.mark.parametrize("model", [PydanticUser, SQLModelUser])
def test_dict_default_uses_aliases(
model: Union[Type[PydanticUser], Type[SQLModelUser]],
):
user = model(fullName="Dana")
data = user.dict(by_alias=True)
if VERSION.startswith("2."):
data = user.model_dump(by_alias=True)
else:
data = user.dict(by_alias=True)
assert "fullName" in data
assert "full_name" not in data
assert data["fullName"] == "Dana"


# Test json by alias


@pytest.mark.parametrize("model", [PydanticUser, SQLModelUser])
def test_json_by_alias(
model: Union[Type[PydanticUser], Type[SQLModelUser]],
):
user = model(fullName="Frank")
json_data = user.json(by_alias=True)
if VERSION.startswith("2."):
json_data = user.model_dump_json(by_alias=True)
else:
json_data = user.json(by_alias=True)
assert ('"fullName":"Frank"' in json_data) or ('"fullName": "Frank"' in json_data)
assert "full_name" not in json_data


# Pydantic v2 specific models - only define if we're running Pydantic v2
if VERSION.startswith("2."):

class PydanticUserV2(BaseModel):
Expand All @@ -148,6 +138,24 @@ class SQLModelUserV2(SQLModel):
SQLModelUserV2 = None


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")


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"
):
Field(serialization_alias="bar")


@needs_pydanticv2
@pytest.mark.parametrize("model", [PydanticUserV2, SQLModelUserV2])
def test_create_with_validation_alias(
Expand All @@ -157,16 +165,13 @@ def test_create_with_validation_alias(
assert user.first_name == "John"


@pytest.mark.skipif(
not VERSION.startswith("2."),
reason="validation_alias and serialization_alias are not supported in Pydantic v1",
)
@needs_pydanticv2
@pytest.mark.parametrize("model", [PydanticUserV2, SQLModelUserV2])
def test_serialize_with_serialization_alias(
model: Union[Type[PydanticUserV2], Type[SQLModelUserV2]],
):
user = model(firstName="Jane")
data = user.dict(by_alias=True)
data = user.model_dump(by_alias=True)
assert "f_name" in data
assert "firstName" not in data
assert "first_name" not in data
Expand Down
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