Fix validation_alias behavior with model_construct for `AliasChoi…

…ces` and `AliasPath` (#9223)

pydantic/aliases.py

@@ -2,7 +2,9 @@
 from __future__ import annotations
 
 import dataclasses
-from typing import Callable, Literal
+from typing import Any, Callable, Literal
+
+from pydantic_core import PydanticUndefined
 
 from ._internal import _internal_dataclass
 
@@ -32,6 +34,23 @@ def convert_to_aliases(self) -> list[str | int]:
         """
         return self.path
 
+    def search_dict_for_path(self, d: dict) -> Any:
+        """Searches a dictionary for the path specified by the alias.
+
+        Returns:
+            The value at the specified path, or `PydanticUndefined` if the path is not found.
+        """
+        v = d
+        for k in self.path:
+            if isinstance(v, str):
+                # disallow indexing into a str, like for AliasPath('x', 0) and x='abc'
+                return PydanticUndefined
+            try:
+                v = v[k]
+            except (KeyError, IndexError, TypeError):
+                return PydanticUndefined
+        return v
+
 
 @dataclasses.dataclass(**_internal_dataclass.slots_true)
 class AliasChoices:

pydantic/main.py

@@ -27,6 +27,7 @@
     _utils,
 )
 from ._migration import getattr_migration
+from .aliases import AliasChoices, AliasPath
 from .annotated_handlers import GetCoreSchemaHandler, GetJsonSchemaHandler
 from .config import ConfigDict
 from .errors import PydanticUndefinedAnnotation, PydanticUserError
@@ -197,7 +198,7 @@ def model_fields_set(self) -> set[str]:
         return self.__pydantic_fields_set__
 
     @classmethod
-    def model_construct(cls: type[Model], _fields_set: set[str] | None = None, **values: Any) -> Model:
+    def model_construct(cls: type[Model], _fields_set: set[str] | None = None, **values: Any) -> Model:  # noqa: C901
         """Creates a new instance of the `Model` class with validated data.
 
         Creates a new model setting `__dict__` and `__pydantic_fields_set__` from trusted or pre-validated data.
@@ -225,14 +226,32 @@ def model_construct(cls: type[Model], _fields_set: set[str] | None = None, **val
             if field.alias is not None and field.alias in values:
                 fields_values[name] = values.pop(field.alias)
                 fields_set.add(name)
-            elif field.validation_alias is not None and field.validation_alias in values:
-                fields_values[name] = values.pop(field.validation_alias)
-                fields_set.add(name)
-            elif name in values:
-                fields_values[name] = values.pop(name)
-                fields_set.add(name)
-            elif not field.is_required():
-                fields_values[name] = field.get_default(call_default_factory=True)
+
+            if (name not in fields_set) and (field.validation_alias is not None):
+                validation_aliases: list[str | AliasPath] = (
+                    field.validation_alias.choices
+                    if isinstance(field.validation_alias, AliasChoices)
+                    else [field.validation_alias]
+                )
+
+                for alias in validation_aliases:
+                    if isinstance(alias, str) and alias in values:
+                        fields_values[name] = values.pop(alias)
+                        fields_set.add(name)
+                        break
+                    elif isinstance(alias, AliasPath):
+                        value = alias.search_dict_for_path(values)
+                        if value is not PydanticUndefined:
+                            fields_values[name] = value
+                            fields_set.add(name)
+                            break
+
+            if name not in fields_set:
+                if name in values:
+                    fields_values[name] = values.pop(name)
+                    fields_set.add(name)
+                elif not field.is_required():
+                    fields_values[name] = field.get_default(call_default_factory=True)
         if _fields_set is None:
             _fields_set = fields_set
 

tests/test_construction.py

@@ -4,7 +4,7 @@
 import pytest
 from pydantic_core import PydanticUndefined, ValidationError
 
-from pydantic import BaseModel, ConfigDict, Field, PrivateAttr, PydanticDeprecatedSince20
+from pydantic import AliasChoices, AliasPath, BaseModel, ConfigDict, Field, PrivateAttr, PydanticDeprecatedSince20
 
 
 class Model(BaseModel):
@@ -561,3 +561,29 @@ class MyModel(BaseModel):
 
     assert m._a == 'a'
     assert '_a' in m.__pydantic_private__
+
+
+def test_model_construct_with_alias_choices() -> None:
+    class MyModel(BaseModel):
+        a: str = Field(validation_alias=AliasChoices('aaa', 'AAA'))
+
+    assert MyModel.model_construct(a='a_value').a == 'a_value'
+    assert MyModel.model_construct(aaa='a_value').a == 'a_value'
+    assert MyModel.model_construct(AAA='a_value').a == 'a_value'
+
+
+def test_model_construct_with_alias_path() -> None:
+    class MyModel(BaseModel):
+        a: str = Field(validation_alias=AliasPath('aaa', 'AAA'))
+
+    assert MyModel.model_construct(a='a_value').a == 'a_value'
+    assert MyModel.model_construct(aaa={'AAA': 'a_value'}).a == 'a_value'
+
+
+def test_model_construct_with_alias_choices_and_path() -> None:
+    class MyModel(BaseModel):
+        a: str = Field(validation_alias=AliasChoices('aaa', AliasPath('AAA', 'aaa')))
+
+    assert MyModel.model_construct(a='a_value').a == 'a_value'
+    assert MyModel.model_construct(aaa='a_value').a == 'a_value'
+    assert MyModel.model_construct(AAA={'aaa': 'a_value'}).a == 'a_value'