get_class_decorator_hook_2: fix fullname

mypy/semanal.py

@@ -1826,8 +1826,8 @@ def apply_class_plugin_hooks(self, defn: ClassDef) -> None:
 
     def get_fullname_for_hook(self, expr: Expression) -> str | None:
         if isinstance(expr, CallExpr):
-            return self.get_fullname_for_hook(expr.callee)
-        elif isinstance(expr, IndexExpr):
+            expr = expr.callee
+        if isinstance(expr, IndexExpr):
             return self.get_fullname_for_hook(expr.base)
         elif isinstance(expr, RefExpr):
             if expr.fullname:

test-data/unit/check-custom-plugin.test

@@ -1029,3 +1029,50 @@ reveal_type(1)  # N: Revealed type is "Literal[1]?"
 [file mypy.ini]
 \[mypy]
 plugins=<ROOT>/test-data/unit/plugins/custom_errorcode.py
+
+[case testClassDecoratorHook2]
+# flags: --config-file tmp/mypy.ini
+from typing import Any, TypeVar
+T = TypeVar('T')
+
+def my_decorator(t: Any) -> Any:
+    raise
+
+@my_decorator
+class C:
+    pass
+
+obj = C()
+reveal_type(obj.magic)  # N: Revealed type is "builtins.str"
+[file mypy.ini]
+\[mypy]
+plugins=<ROOT>/test-data/unit/plugins/class_decorator_hook_2.py
+
+[typing fixtures/typing-medium.pyi]
+
+[case testClassDecoratorHook2_incorrect]
+# flags: --config-file tmp/mypy.ini
+from typing import Any, TypeVar
+T = TypeVar('T')
+
+def my_decorator(t: Any) -> Any:
+    raise
+
+@my_decorator()()
+class C:
+    pass
+
+obj = C()
+_ = obj.magic
+[out]
+main:8: error: invalid syntax
+
+[out version>=3.9]
+main:8: error: Missing positional argument "t" in call to "my_decorator"
+main:13: error: "C" has no attribute "magic"
+
+[file mypy.ini]
+\[mypy]
+plugins=<ROOT>/test-data/unit/plugins/class_decorator_hook_2.py
+
+[typing fixtures/typing-medium.pyi]

test-data/unit/check-dataclasses.test

@@ -2515,3 +2515,22 @@ a: MyDataclass
 b = [a, a]  # trigger joining the types
 
 [builtins fixtures/dataclasses.pyi]
+
+[case testDataclassesInvalidDecorator]
+from dataclasses import dataclass
+
+@dataclass()()
+class C:
+    a: str
+
+reveal_type(C)
+
+[out]
+main:3: error: invalid syntax
+
+[out version>=3.9]
+main:3: error: Too few arguments
+main:4: error: Cannot instantiate type "Type[Never]"
+main:7: note: Revealed type is "def () -> __main__.C"
+
+[builtins fixtures/dataclasses.pyi]

test-data/unit/plugins/class_decorator_hook_2.py

@@ -0,0 +1,22 @@
+from __future__ import annotations
+
+from typing import Callable
+
+from mypy.plugin import ClassDefContext, Plugin
+from mypy.plugins.common import add_attribute_to_class
+
+
+class MyPlugin(Plugin):
+    def get_class_decorator_hook_2(self, fullname: str) -> Callable[[ClassDefContext], bool] | None:
+        if fullname == "__main__.my_decorator":
+            return transform_hook
+        return None
+
+
+def transform_hook(ctx: ClassDefContext) -> bool:
+    add_attribute_to_class(ctx.api, ctx.cls, 'magic', ctx.api.named_type('builtins.str'))
+    return True
+
+
+def plugin(version: str) -> type[MyPlugin]:
+    return MyPlugin