Minor improvements to the dataclasses overlay

* Relaxed type checking for dataclasses with unknown/dynamic base classes.
  The set of fields for such dataclasses is unknown, so we cannot precisely
  check instantiation and `dataclasses.replace` calls.
* Allowed inheriting `__match_args__`.
* Ensured that `kw_only=` fields are excluded from `__match_args__`.

PiperOrigin-RevId: 826512868

Author: superbobry

pytype/abstract/_classes.py

@@ -429,12 +429,19 @@ def __init__(
       self._populate_decorator_metadata()
     if "__dataclass_fields__" in self.metadata:
       self.match_args = tuple(
-          attr.name for attr in self.metadata["__dataclass_fields__"]
+          attr.name
+          for attr in self.metadata["__dataclass_fields__"]
+          if not attr.kw_only
       )
     elif self.load_lazy_attribute("__match_args__"):
       self.match_args = self._convert_str_tuple("__match_args__") or ()
     else:
-      self.match_args = ()
+      for base in self.mro[1:]:
+        if isinstance(base, class_mixin.Class) and hasattr(base, "match_args"):
+          self.match_args = base.match_args
+          break
+      else:
+        self.match_args = ()
 
   @classmethod
   def make(

pytype/overlays/classgen.py

@@ -119,8 +119,21 @@ def make_init(self, node, cls, attrs, init_method_name="__init__"):
       else:
         pos_params.append(param)
 
+    # If the class has unknown bases or is dynamic, we can't know all possible
+    # fields, so accept arbitrary positional and keyword arguments.
+    has_unknown_fields = (
+        self.ctx.convert.unsolvable in cls.mro or cls.is_dynamic
+    )
+
     return overlay_utils.make_method(
-        self.ctx, node, init_method_name, pos_params, 0, kwonly_params
+        self.ctx,
+        node,
+        init_method_name,
+        pos_params,
+        posonly_count=0,
+        kwonly_params=kwonly_params,
+        varargs=Param("args") if has_unknown_fields else None,
+        kwargs=Param("kwargs") if has_unknown_fields else None,
     )
 
   def call(self, node, func, args, alias_map=None):

pytype/overlays/dataclass_overlay.py

@@ -293,13 +293,18 @@ def _match_args_sequentially(self, node, args, alias_map, match_all_views):
     fields = obj.cls.metadata["__dataclass_fields__"]
     # 0 or more fields can be replaced, so we give every field a default.
     default = self.ctx.new_unsolvable(node)
+    # If the class has unknown bases or is dynamic, we can't know all possible
+    # fields, so we accept arbitrary keyword arguments via kwargs_name.
+    has_unknown_fields = (
+        self.ctx.convert.unsolvable in obj.cls.mro or obj.cls.is_dynamic
+    )
     replace = abstract.SimpleFunction.build(
         name=self.name,
         param_names=("obj",),
         posonly_count=1,
         varargs_name=None,
         kwonly_params=tuple(f.name for f in fields),
-        kwargs_name=None,
+        kwargs_name="kwargs" if has_unknown_fields else None,
         defaults={f.name: default for f in fields},
         annotations={f.name: f.typ for f in fields},
         ctx=self.ctx,

pytype/tests/test_dataclasses.py

@@ -147,6 +147,33 @@ def __init__(self, a: bool) -> None: ...
     """,
     )
 
+  def test_init_unknown_base(self):
+    self.CheckWithErrors("""
+      import dataclasses
+      from foo import Base  # pytype: disable=import-error
+      @dataclasses.dataclass
+      class A(Base):
+        x: int
+      A(x=42)
+      A(x="wrong")  # wrong-arg-types
+      A(x=42, y="from_base")
+      A(42, "from_base")
+    """)
+
+  def test_init_dynamic_base(self):
+    self.CheckWithErrors("""
+      import dataclasses
+      class Base:
+        _HAS_DYNAMIC_ATTRIBUTES = True
+      @dataclasses.dataclass
+      class A(Base):
+        x: int
+      A(x=42)
+      A(x="wrong")  # wrong-arg-types
+      A(x=42, y="from_base")
+      A(42, "from_base")
+    """)
+
   def test_field(self):
     ty = self.Infer("""
       from typing import List
@@ -968,6 +995,31 @@ class C:
         errors, {"e": ["Expected", "str", "Actual", "int"]}
     )
 
+  def test_replace_unknown_base(self):
+    self.CheckWithErrors("""
+      import dataclasses
+      from foo import Base  # pytype: disable=import-error
+      @dataclasses.dataclass
+      class A(Base):
+        x: int
+      a = A(x=42)
+      dataclasses.replace(a, x="wrong")  # wrong-arg-types
+      dataclasses.replace(a, y="from_base")
+    """)
+
+  def test_replace_dynamic_base(self):
+    self.CheckWithErrors("""
+      import dataclasses
+      class Base:
+        _HAS_DYNAMIC_ATTRIBUTES = True
+      @dataclasses.dataclass
+      class A(Base):
+        x: int
+      a = A(x=42)
+      dataclasses.replace(a, x="wrong")  # wrong-arg-types
+      dataclasses.replace(a, y="from_base")
+    """)
+
 
 class TestPyiDataclass(test_base.BaseTest):
   """Tests for @dataclasses in pyi files."""
@@ -1718,6 +1770,57 @@ def f(x, y):
               print("not matched")
       """)
 
+  def test_inheritance(self):
+    with self.DepTree([(
+        "foo.pyi",
+        """
+      import dataclasses
+      @dataclasses.dataclass
+      class Point:
+        x: float
+        y: float
+
+      class OtherPoint(Point):
+        ...
+    """,
+    )]):
+      self.Check("""
+        import foo
+        def f(x, y):
+          p = foo.OtherPoint(x, y)
+          match p:
+            case foo.OtherPoint(x, y):
+              print(f"({x}, {y})")
+            case _:
+              print("not matched")
+      """)
+
+  def test_kw_only(self):
+    with self.DepTree([(
+        "foo.pyi",
+        """
+      import dataclasses
+      @dataclasses.dataclass
+      class Point:
+        x: float
+        _: dataclasses.KW_ONLY
+        y: float
+
+      class PointWithKwOnly(Point):
+        ...
+    """,
+    )]):
+      self.CheckWithErrors("""
+        import foo
+        def f(x, y):
+          p = foo.PointWithKwOnly(x, y=y)
+          match p:
+            case foo.PointWithKwOnly(x, y):  # match-error
+              print(f"({x}, {y})")
+            case _:
+              print("not matched")
+      """)
+
 
 if __name__ == "__main__":
   test_base.main()