Fixed Expr.__setattr__ for subclasses (dask#11845)

Author: TomAugspurger

dask/_expr.py

@@ -176,7 +176,7 @@ def __setattr__(self, name: str, value: Any) -> None:
             object.__setattr__(self, name, value)
             return
         try:
-            params = object.__getattribute__(type(self), "_parameters")
+            params = type(self)._parameters
             operands = object.__getattribute__(self, "operands")
             operands[params.index(name)] = value
         except ValueError:

dask/tests/test_expr.py

@@ -5,12 +5,26 @@
 from dask._expr import Expr
 
 
-def test_setattr():
-    class MyExpr(Expr):
-        _parameters = ["foo", "bar"]
+class MyExpr(Expr):
+    _parameters = ["foo", "bar"]
+
+
+class MyExpr2(MyExpr):
+    # A subclass that inherits parameters
+    pass
 
+
+def test_setattr():
     e = MyExpr(foo=1, bar=2)
     e.bar = 3
     assert e.bar == 3
     with pytest.raises(AttributeError):
         e.baz = 4
+
+
+def test_setattr2():
+    e = MyExpr2(foo=1, bar=2)
+    e.bar = 3
+    assert e.bar == 3
+    with pytest.raises(AttributeError):
+        e.baz = 4