Detect `'@' dotted_name '(' ')' NEWLINE` as a simple decorator (#2182)

Previously the RELAXED_DECORATOR detection would be falsely True on that
example. The problem was that an argument-less parentheses pair didn't
pass the `is_simple_decorator_trailer` check even it should. OTOH a
parentheses pair containing an argument or more passed as expected.

diff --git a/CHANGES.md b/CHANGES.md
index 7741d92772d1065e88b65d90c543e5852fb4070c..00d6782dc6b09198e3550b6ce0ad487c4653e381 100644 (file)
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -7,6 +7,9 @@
 - Set `--pyi` mode if `--stdin-filename` ends in `.pyi` (#2169)
 - Add `--no-diff` to black-primer to suppress formatting changes (#2187)
 
+- Stop detecting target version as Python 3.9+ with pre-PEP-614 decorators that are
+  being called but with no arguments (#2182)
+
 ### 21.4b2
 
 #### _Black_

diff --git a/src/black/__init__.py b/src/black/__init__.py
index 49d088b531d0bc48f3340f576db6659ad0da8a03..cf257876c035c27d94c1348212a55fc59a7e7f64 100644 (file)
--- a/src/black/__init__.py
+++ b/src/black/__init__.py
@@ -5761,6 +5761,13 @@ def is_simple_decorator_trailer(node: LN, last: bool = False) -> bool:
             and node.children[0].type == token.DOT
             and node.children[1].type == token.NAME
         )
+        # last trailer can be an argument-less parentheses pair
+        or (
+            last
+            and len(node.children) == 2
+            and node.children[0].type == token.LPAR
+            and node.children[1].type == token.RPAR
+        )
         # last trailer can be arguments
         or (
             last

diff --git a/tests/data/decorators.py b/tests/data/decorators.py
index acfad51fcb8ddee843314f64868821baaed717e9..a0f38ca7b9d411c3d82ca11dafffc77a466dc7ba 100644 (file)
--- a/tests/data/decorators.py
+++ b/tests/data/decorators.py
@@ -13,6 +13,12 @@ def f():
 
 ##
 
+@decorator()
+def f():
+    ...
+
+##
+
 @decorator(arg)
 def f():
     ...