Fix validation_alias behavior with model_construct for AliasChoices and AliasPath

[sydney-runkle]

Fix #9216
Fix #9220

Initially introduced in #9144 because we forgot to account for AliasPath and AliasChoices validation aliases!

Selected Reviewer: @adriangb

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[codspeed-hq]

CodSpeed Performance Report

Merging #9223 will not alter performance

_{Comparing full_alias_fix (c1d585f) with main (59eace3)}

Summary

✅ 13 untouched benchmarks

[sydney-runkle]

Please review

[dmontagu]

One potential issue with this approach — the following code errors for normal validation:

from pydantic import BaseModel, AliasPath, Field


class MyModel(BaseModel):
    x: str = Field(alias=AliasPath('y', 1))

print(MyModel(y=['abc', 'def']))

print(MyModel(y='abc'))
"""
y.1
  Field required [type=missing, input_value={'y': 'abc'}, input_type=dict]
"""

and if you add a default, you get the default:

from pydantic import BaseModel, AliasPath, Field


class MyModel(BaseModel):
    x: str = Field(default='xyz', alias=AliasPath('y', 1))

print(MyModel(y=['abc', 'def']))
#> x='def'

print(MyModel(y='abc'))
#> x='xyz'

However, with your current implementation, if you use model_construct I believe you'd end up with:

from pydantic import BaseModel, AliasPath, Field


class MyModel(BaseModel):
    x: str = Field(default='xyz', alias=AliasPath('y', 1))

print(MyModel.model_construct(y=['abc', 'def']))
#> x='def'  (as expected)

print(MyModel.model_construct(y='abc'))
#> x='b'  (not expected)

Not sure if this is a blocking-level problem, or if it's worth the overhead it would add to prevent this misbehavior.

[sydney-runkle]

Just added an isinstance(v, str) check to prevent that behavior, which now results in:

from pydantic import BaseModel, AliasPath, Field


class MyModel(BaseModel):
    x: str = Field(default='xyz', validation_alias=AliasPath('y', 1))

print(MyModel.model_construct(y=['abc', 'def']))
#> x='def'  (as expected)

print(MyModel.model_construct(y='abc'))
#> x='xyz'  (as expected)