Make blank_line_after_nested_stub_class work for methods (#4141)

Fixes #4113

Authored by dhruvmanila

CHANGES.md

@@ -21,6 +21,7 @@
 - Remove empty lines before docstrings in async functions (#4132)
 - Address a missing case in the change to allow empty lines at the beginning of all
   blocks, except immediately before a docstring (#4130)
+- For stubs, fix logic to enforce empty line after nested classes with bodies (#4141)
 
 ### Configuration
 

src/black/lines.py

@@ -640,15 +640,15 @@ def _maybe_empty_lines(self, current_line: Line) -> Tuple[int, int]:
         if previous_def is not None:
             assert self.previous_line is not None
             if self.mode.is_pyi:
-                if depth and not current_line.is_def and self.previous_line.is_def:
+                if (
-                    # Empty lines between attributes and methods should be preserved.
-                    before = 1 if user_had_newline else 0
-                elif (
                     Preview.blank_line_after_nested_stub_class in self.mode
                     and previous_def.is_class
                     and not previous_def.is_stub_class
                 ):
                     before = 1
+                elif depth and not current_line.is_def and self.previous_line.is_def:
+                    # Empty lines between attributes and methods should be preserved.
+                    before = 1 if user_had_newline else 0
                 elif depth:
                     before = 0
                 else:

tests/data/cases/nested_stub.py

@@ -18,6 +18,18 @@ def function_definition(self): ...
         assignment = 1
     def f2(self) -> str: ...
 
+
+class TopLevel:
+    class Nested1:
+        foo: int
+        def bar(self): ...
+    field = 1
+
+    class Nested2:
+        def bar(self): ...
+        foo: int
+    field = 1
+
 # output
 
 import sys
@@ -42,3 +54,16 @@ def function_definition(self): ...
         assignment = 1
 
     def f2(self) -> str: ...
+
+class TopLevel:
+    class Nested1:
+        foo: int
+        def bar(self): ...
+
+    field = 1
+
+    class Nested2:
+        def bar(self): ...
+        foo: int
+
+    field = 1