feat(model_construct): handle partially hydrated models

pydantic_changedetect/changedetect.py

@@ -99,6 +99,10 @@ def model_changed_fields(self) -> Set[str]:
 
         changed_fields = self.model_self_changed_fields.copy()
         for field_name, model_field in self_compat.model_fields.items():
+            # Support for instances created through model_construct, when not all fields have been defined
+            if field_name not in self.__dict__:
+                continue
+
             field_value = self.__dict__[field_name]
 
             # Value is a ChangeDetectionMixin instance itself

tests/test_changedetect.py

@@ -14,6 +14,11 @@ class Something(ChangeDetectionMixin, pydantic.BaseModel):
     id: int
 
 
+class SomethingMultipleFields(ChangeDetectionMixin, pydantic.BaseModel):
+    id: int
+    foo: str
+
+
 class Unsupported(pydantic.BaseModel):
     id: int
 
@@ -479,6 +484,17 @@ def test_model_construct_works():
     assert something.model_has_changed is True
 
 
+@pytest.mark.skipif(PYDANTIC_V1, reason="pydantic v1 does not support model_construct()")
+def test_model_construct_works_for_models_loaded_with_few_fields():
+    something_multiple_fields = SomethingMultipleFields.model_construct(id=1)
+
+    assert something_multiple_fields.model_has_changed is False
+
+    something_multiple_fields.id = 2
+
+    assert something_multiple_fields.model_has_changed is True
+
+
 @pytest.mark.skipif(PYDANTIC_V1, reason="pydantic v1 does not trigger warnings")
 def test_construct_works_on_v2():
     with pytest.warns(DeprecationWarning):