From 61d8400e42c471baed2ab4a122a195b03a09a1bf Mon Sep 17 00:00:00 2001
From: Yilei Yang <yileiyang@google.com>
Date: Mon, 6 Nov 2023 12:07:21 -0800
Subject: [PATCH] Keep requiring two empty lines between module-level docstring
 and first function or class definition.

Fixes #4027.
---
 CHANGES.md                                            |  2 ++
 src/black/lines.py                                    |  1 +
 .../data/cases/module_docstring_followed_by_class.py  | 11 +++++++++++
 .../cases/module_docstring_followed_by_function.py    | 11 +++++++++++
 4 files changed, 25 insertions(+)
 create mode 100644 tests/data/cases/module_docstring_followed_by_class.py
 create mode 100644 tests/data/cases/module_docstring_followed_by_function.py

diff --git a/CHANGES.md b/CHANGES.md
index 97084a2bfc1..a68f87bfc12 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -19,6 +19,8 @@
   indented less (#3964)
 - Multiline list and dict unpacking as the sole argument to a function is now also
   indented less (#3992)
+- Keep requiring two empty lines between module-level docstring and first function or
+  class definition. (#4028)
 
 ### Configuration
 
diff --git a/src/black/lines.py b/src/black/lines.py
index a73c429e3d9..23c1a93d3d4 100644
--- a/src/black/lines.py
+++ b/src/black/lines.py
@@ -578,6 +578,7 @@ def maybe_empty_lines(self, current_line: Line) -> LinesBlock:
             and self.previous_block.previous_block is None
             and len(self.previous_block.original_line.leaves) == 1
             and self.previous_block.original_line.is_triple_quoted_string
+            and not (current_line.is_class or current_line.is_def)
         ):
             before = 1
 
diff --git a/tests/data/cases/module_docstring_followed_by_class.py b/tests/data/cases/module_docstring_followed_by_class.py
new file mode 100644
index 00000000000..6fdbfc8c240
--- /dev/null
+++ b/tests/data/cases/module_docstring_followed_by_class.py
@@ -0,0 +1,11 @@
+# flags: --preview
+"""Two blank lines between module docstring and a class."""
+class MyClass:
+    pass
+
+# output
+"""Two blank lines between module docstring and a class."""
+
+
+class MyClass:
+    pass
diff --git a/tests/data/cases/module_docstring_followed_by_function.py b/tests/data/cases/module_docstring_followed_by_function.py
new file mode 100644
index 00000000000..5913a59e1fe
--- /dev/null
+++ b/tests/data/cases/module_docstring_followed_by_function.py
@@ -0,0 +1,11 @@
+# flags: --preview
+"""Two blank lines between module docstring and a function def."""
+def function():
+    pass
+
+# output
+"""Two blank lines between module docstring and a function def."""
+
+
+def function():
+    pass