feat: support default_factory with BaseModel.construct

closes pydantic#1732

changes/1732-PrettyWood.md

@@ -0,0 +1 @@
+support `default_factory` with `BaseModel.construct`

pydantic/main.py

@@ -527,7 +527,10 @@ def construct(cls: Type['Model'], _fields_set: Optional['SetStr'] = None, **valu
         Default values are respected, but no other validation is performed.
         """
         m = cls.__new__(cls)
-        object.__setattr__(m, '__dict__', {**deepcopy(cls.__field_defaults__), **values})
+        # default field values
+        fields_values = {name: field.get_default() for name, field in cls.__fields__.items() if not field.required}
+        fields_values.update(values)
+        object.__setattr__(m, '__dict__', fields_values)
         if _fields_set is None:
             _fields_set = set(values.keys())
         object.__setattr__(m, '__fields_set__', _fields_set)

tests/test_construction.py

@@ -3,7 +3,7 @@
 
 import pytest
 
-from pydantic import BaseModel
+from pydantic import BaseModel, Field
 
 
 class Model(BaseModel):
@@ -275,3 +275,13 @@ class X(BaseModel):
     # deep['deep_thing'] gets modified
     assert x.deep['deep_thing'] == [1, 2, 3]
     assert y.deep['deep_thing'] == [1, 2, 3]
+
+
+def test_construct_default_factory():
+    class Model(BaseModel):
+        foo: List[int] = Field(default_factory=list)
+        bar: str = 'Baz'
+
+    m = Model.construct()
+    assert m.foo == []
+    assert m.bar == 'Baz'