From 29dd25725303992d36c3a75c3a071080ac06085f Mon Sep 17 00:00:00 2001
From: "Yilei \"Dolee\" Yang" <yileiyang@google.com>
Date: Tue, 20 Dec 2022 17:58:02 -0800
Subject: [PATCH] Fix an issue where extra empty lines are added. (#3470)

---
 CHANGES.md                      |  2 ++
 src/black/lines.py              |  3 +-
 tests/data/preview/comments9.py | 51 +++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index e2c5adf..c07d81d 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -23,6 +23,8 @@
   regular and f-strings start with an empty span (#3463)
 - Fix a crash in preview advanced string processing where a standalone comment is placed
   before a dict's value (#3469)
+- Fix an issue where extra empty lines are added when a decorator has `# fmt: skip`
+  applied or there is a standalone comment between decorators (#3470)
 - Do not put the closing quotes in a docstring on a separate line, even if the line is
   too long (#3430)
 - Long values in dict literals are now wrapped in parentheses; correspondingly
diff --git a/src/black/lines.py b/src/black/lines.py
index 08281bc..2aa675c 100644
--- a/src/black/lines.py
+++ b/src/black/lines.py
@@ -520,7 +520,8 @@ class EmptyLineTracker:
                 and (self.semantic_leading_comment is None or before)
             ):
                 self.semantic_leading_comment = block
-        elif not current_line.is_decorator:
+        # `or before` means this decorator already has an empty line before
+        elif not current_line.is_decorator or before:
             self.semantic_leading_comment = None
 
         self.previous_line = current_line
diff --git a/tests/data/preview/comments9.py b/tests/data/preview/comments9.py
index 449612c..77b2555 100644
--- a/tests/data/preview/comments9.py
+++ b/tests/data/preview/comments9.py
@@ -114,6 +114,31 @@ class MyClass:
         pass
 
 
+# Regression test for https://github.com/psf/black/issues/3454.
+def foo():
+    pass
+    # Trailing comment that belongs to this function
+
+
+@decorator1
+@decorator2  # fmt: skip
+def bar():
+    pass
+
+
+# Regression test for https://github.com/psf/black/issues/3454.
+def foo():
+    pass
+    # Trailing comment that belongs to this function.
+    # NOTE this comment only has one empty line below, and the formatter
+    # should enforce two blank lines.
+
+@decorator1
+# A standalone comment
+def bar():
+    pass
+
+
 # output
 
 
@@ -252,3 +277,29 @@ class MyClass:
     # More comments.
     def first_method(self):
         pass
+
+
+# Regression test for https://github.com/psf/black/issues/3454.
+def foo():
+    pass
+    # Trailing comment that belongs to this function
+
+
+@decorator1
+@decorator2  # fmt: skip
+def bar():
+    pass
+
+
+# Regression test for https://github.com/psf/black/issues/3454.
+def foo():
+    pass
+    # Trailing comment that belongs to this function.
+    # NOTE this comment only has one empty line below, and the formatter
+    # should enforce two blank lines.
+
+
+@decorator1
+# A standalone comment
+def bar():
+    pass
-- 
2.39.2