relax validation rules on decorators

libcst/_nodes/statement.py

@@ -21,7 +21,6 @@
     BaseAssignTargetExpression,
     BaseDelTargetExpression,
     BaseExpression,
-    Call,
     ConcatenatedString,
     ExpressionPosition,
     From,
@@ -1619,7 +1618,7 @@ class Decorator(CSTNode):
 
     #: The decorator that will return a new function wrapping the parent
     #: of this decorator.
-    decorator: Union[Name, Attribute, Call]
+    decorator: BaseExpression
 
     #: Line comments and empty lines before this decorator. The parent
     #: :class:`FunctionDef` or :class:`ClassDef` node owns leading lines before
@@ -1632,19 +1631,6 @@ class Decorator(CSTNode):
     #: Optional trailing comment and newline following the decorator before the next line.
     trailing_whitespace: TrailingWhitespace = TrailingWhitespace.field()
 
-    def _validate(self) -> None:
-        decorator = self.decorator
-        if len(decorator.lpar) > 0 or len(decorator.rpar) > 0:
-            raise CSTValidationError(
-                "Cannot have parens around decorator in a Decorator."
-            )
-        if isinstance(decorator, Call) and not isinstance(
-            decorator.func, (Name, Attribute)
-        ):
-            raise CSTValidationError(
-                "Decorator call function must be Name or Attribute node."
-            )
-
     def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "Decorator":
         return Decorator(
             leading_lines=visit_sequence(

libcst/_nodes/tests/test_funcdef.py

@@ -623,6 +623,46 @@ class FunctionDefCreationTest(CSTNodeTest):
                 "code": "@ bar (  )\n",
                 "expected_position": CodeRange((1, 0), (1, 10)),
             },
+            # Allow nested calls on decorator
+            {
+                "node": cst.FunctionDef(
+                    cst.Name("foo"),
+                    cst.Parameters(),
+                    cst.SimpleStatementSuite((cst.Pass(),)),
+                    (cst.Decorator(cst.Call(func=cst.Call(func=cst.Name("bar")))),),
+                ),
+                "code": "@bar()()\ndef foo(): pass\n",
+            },
+            # Allow any expression in decorator
+            {
+                "node": cst.FunctionDef(
+                    cst.Name("foo"),
+                    cst.Parameters(),
+                    cst.SimpleStatementSuite((cst.Pass(),)),
+                    (
+                        cst.Decorator(
+                            cst.BinaryOperation(cst.Name("a"), cst.Add(), cst.Name("b"))
+                        ),
+                    ),
+                ),
+                "code": "@a + b\ndef foo(): pass\n",
+            },
+            # Allow parentheses around decorator
+            {
+                "node": cst.FunctionDef(
+                    cst.Name("foo"),
+                    cst.Parameters(),
+                    cst.SimpleStatementSuite((cst.Pass(),)),
+                    (
+                        cst.Decorator(
+                            cst.Name(
+                                "bar", lpar=(cst.LeftParen(),), rpar=(cst.RightParen(),)
+                            )
+                        ),
+                    ),
+                ),
+                "code": "@(bar)\ndef foo(): pass\n",
+            },
             # Parameters
             {
                 "node": cst.Parameters(
@@ -922,22 +962,6 @@ def test_valid_native(self, **kwargs: Any) -> None:
                 ),
                 r"Expecting a star prefix of '\*\*'",
             ),
-            # Validate decorator name semantics
-            (
-                lambda: cst.FunctionDef(
-                    cst.Name("foo"),
-                    cst.Parameters(),
-                    cst.SimpleStatementSuite((cst.Pass(),)),
-                    (
-                        cst.Decorator(
-                            cst.Name(
-                                "bar", lpar=(cst.LeftParen(),), rpar=(cst.RightParen(),)
-                            )
-                        ),
-                    ),
-                ),
-                "Cannot have parens around decorator in a Decorator",
-            ),
         )
     )
     def test_invalid(

libcst/matchers/__init__.py

@@ -3089,13 +3089,6 @@ class Continue(BaseSmallStatement, BaseMatcherNode):
     ] = DoNotCare()
 
 
-NameOrAttributeOrCallMatchType = Union[
-    "Name",
-    "Attribute",
-    "Call",
-    MetadataMatchType,
-    MatchIfTrue[Union[cst.Name, cst.Attribute, cst.Call]],
-]
 TrailingWhitespaceMatchType = Union[
     "TrailingWhitespace", MetadataMatchType, MatchIfTrue[cst.TrailingWhitespace]
 ]
@@ -3104,10 +3097,10 @@ class Continue(BaseSmallStatement, BaseMatcherNode):
 @dataclass(frozen=True, eq=False, unsafe_hash=False)
 class Decorator(BaseMatcherNode):
     decorator: Union[
-        NameOrAttributeOrCallMatchType,
+        BaseExpressionMatchType,
         DoNotCareSentinel,
-        OneOf[NameOrAttributeOrCallMatchType],
-        AllOf[NameOrAttributeOrCallMatchType],
+        OneOf[BaseExpressionMatchType],
+        AllOf[BaseExpressionMatchType],
     ] = DoNotCare()
     leading_lines: Union[
         Sequence[