Handle properties in dataclasses correctly

Author: DanielNoord

ChangeLog

@@ -16,6 +16,15 @@ Release date: TBA
 
   Refs PyCQA/pylint#2567
 
+What's New in astroid 2.12.14?
+==============================
+Release date: TBA
+
+* Handle the effect of properties on the ``__init__`` of a dataclass correctly.
+
+  Closes PyCQA/pylint#5225
+
+
 What's New in astroid 2.12.13?
 ==============================
 Release date: 2022-11-19

astroid/brain/brain_dataclasses.py

@@ -243,6 +243,17 @@ def _generate_dataclass_init(
         name, annotation, value = assign.target.name, assign.annotation, assign.value
         assign_names.append(name)
 
+        # Check whether this assign is overriden by a property assignment
+        property_node: nodes.FunctionDef | None = None
+        for additional_assign in node.locals[name]:
+            if not isinstance(additional_assign, nodes.FunctionDef):
+                continue
+            if not additional_assign.decorators:
+                continue
+            if "builtins.property" in additional_assign.decoratornames():
+                property_node = additional_assign
+                break
+
         if _is_init_var(annotation):  # type: ignore[arg-type] # annotation is never None
             init_var = True
             if isinstance(annotation, nodes.Subscript):
@@ -277,6 +288,14 @@ def _generate_dataclass_init(
                         )
             else:
                 param_str += f" = {value.as_string()}"
+        elif property_node:
+            # We set the result of the property call as default
+            # This hides the fact that this would normally be a 'property object'
+            # But we can't represent those as string
+            try:
+                param_str += f" = {next(property_node.infer_call_result()).as_string()}"
+            except (InferenceError, StopIteration):
+                pass
 
         params.append(param_str)
         if not init_var:

tests/unittest_brain_dataclasses.py

@@ -1114,3 +1114,72 @@ def __init__(self, ef: int = 3):
     third_init: bases.UnboundMethod = next(third.infer())
     assert [a.name for a in third_init.args.args] == ["self", "ef"]
     assert [a.value for a in third_init.args.defaults] == [3]
+
+
+def test_dataclass_with_properties() -> None:
+    """Tests for __init__ creation for dataclasses that use properties."""
+    first, second, third = astroid.extract_node(
+        """
+    from dataclasses import dataclass
+
+    @dataclass
+    class Dataclass:
+        attr: int
+
+        @property
+        def attr(self) -> int:
+            return 1
+
+        @attr.setter
+        def attr(self, value: int) -> None:
+            pass
+
+    class ParentOne(Dataclass):
+        '''Docstring'''
+
+    @dataclass
+    class ParentTwo(Dataclass):
+        '''Docstring'''
+
+    Dataclass.__init__  #@
+    ParentOne.__init__  #@
+    ParentTwo.__init__  #@
+    """
+    )
+
+    first_init: bases.UnboundMethod = next(first.infer())
+    assert [a.name for a in first_init.args.args] == ["self", "attr"]
+    assert [a.value for a in first_init.args.defaults] == [1]
+
+    second_init: bases.UnboundMethod = next(second.infer())
+    assert [a.name for a in second_init.args.args] == ["self", "attr"]
+    assert [a.value for a in second_init.args.defaults] == [1]
+
+    third_init: bases.UnboundMethod = next(third.infer())
+    assert [a.name for a in third_init.args.args] == ["self", "attr"]
+    assert [a.value for a in third_init.args.defaults] == [1]
+
+    fourth = astroid.extract_node(
+        """
+    from dataclasses import dataclass
+
+    @dataclass
+    class Dataclass:
+        other_attr: str
+        attr: str
+
+        @property
+        def attr(self) -> str:
+            return self.other_attr[-1]
+
+        @attr.setter
+        def attr(self, value: int) -> None:
+            pass
+
+    Dataclass.__init__  #@
+    """
+    )
+
+    fourth_init: bases.UnboundMethod = next(fourth.infer())
+    assert [a.name for a in fourth_init.args.args] == ["self", "other_attr", "attr"]
+    assert [a.name for a in fourth_init.args.defaults] == ["Uninferable"]