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Make InitSettingsSource resolution deterministic #681

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Merged
merged 3 commits into from
Sep 22, 2025
Merged

Make InitSettingsSource resolution deterministic #681

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4c8f5e4
Add test to demonstrate non-deterministic nature of `InitSettingsSource`
Sep 17, 2025
eb7b0ef
Make `InitSettingsSource` alias resolution order deterministic
Sep 19, 2025
021cbaa
Mark `test_init_kwargs_alias_resolution_deterministic` as stable
Sep 19, 2025
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3 changes: 2 additions & 1 deletion pydantic_settings/sources/base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -268,8 +268,9 @@ def __init__(
init_kwarg_name = init_kwarg_names & set(alias_names)
if init_kwarg_name:
preferred_alias = alias_names[0]
preferred_set_alias = next(alias for alias in alias_names if alias in init_kwarg_name)
init_kwarg_names -= init_kwarg_name
self.init_kwargs[preferred_alias] = init_kwargs[init_kwarg_name.pop()]
self.init_kwargs[preferred_alias] = init_kwargs[preferred_set_alias]
self.init_kwargs.update({key: val for key, val in init_kwargs.items() if key in init_kwarg_names})

super().__init__(settings_cls)
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10 changes: 10 additions & 0 deletions tests/test_settings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -699,6 +699,16 @@ class Example(BaseSettings):
assert Example(name='john', PREFIX_SURNAME='doe').model_dump() == {'name': 'john', 'last_name': 'doe'}


def test_init_kwargs_alias_resolution_deterministic():
class Example(BaseSettings):
name: str
last_name: str = Field(validation_alias=AliasChoices('surname', 'last_name'))

result = Example(name='john', surname='doe', last_name='smith').model_dump()

assert result == {'name': 'john', 'last_name': 'doe'}


def test_alias_nested_model_default_partial_update():
class SubModel(BaseModel):
v1: str = 'default'
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