Gate behind preview

crates/ruff_python_formatter/src/statement/suite.rs

@@ -516,7 +516,13 @@ impl FormatSuite {
         let existing_newlines =
             lines_after_ignoring_end_of_line_trivia(end_of_def_or_class, f.context().source());
         if existing_newlines < 2 {
-            empty_line().fmt(f)?;
+            if f.context().is_preview() {
+                empty_line().fmt(f)?;
+            } else {
+                if last_def_or_class.is_stmt_class_def() && f.options().source_type().is_stub() {
+                    empty_line().fmt(f)?;
+                }
+            }
         }
         Ok(())
     }

crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__comments9.py.snap

@@ -159,6 +159,22 @@ def bar():
  # leading 3 that already has an empty line
  @deco3
  # leading 4
+@@ -106,7 +105,6 @@
+         # Another leading comment
+         def another_inline():
+             pass
+-
+     else:
+         # More leading comments
+         def inline_after_else():
+@@ -121,7 +119,6 @@
+     # Another leading comment
+     def another_top_level_quote_inline_inline():
+         pass
+-
+ else:
+     # More leading comments
+     def top_level_quote_inline_after_else():
 ```
 
 ## Ruff Output
@@ -271,7 +287,6 @@ def main():
         # Another leading comment
         def another_inline():
             pass
-
     else:
         # More leading comments
         def inline_after_else():
@@ -286,7 +301,6 @@ if a:
     # Another leading comment
     def another_top_level_quote_inline_inline():
         pass
-
 else:
     # More leading comments
     def top_level_quote_inline_after_else():

crates/ruff_python_formatter/tests/snapshots/black_compatibility@cases__function2.py.snap

@@ -0,0 +1,215 @@
+---
+source: crates/ruff_python_formatter/tests/fixtures.rs
+input_file: crates/ruff_python_formatter/resources/test/fixtures/black/cases/function2.py
+---
+## Input
+
+```python
+def f(
+  a,
+  **kwargs,
+) -> A:
+    with cache_dir():
+        if something:
+            result = (
+                CliRunner().invoke(black.main, [str(src1), str(src2), "--diff", "--check"])
+            )
+    limited.append(-limited.pop())  # negate top
+    return A(
+        very_long_argument_name1=very_long_value_for_the_argument,
+        very_long_argument_name2=-very.long.value.for_the_argument,
+        **kwargs,
+    )
+def g():
+    "Docstring."
+    def inner():
+        pass
+    print("Inner defs should breathe a little.")
+def h():
+    def inner():
+        pass
+    print("Inner defs should breathe a little.")
+
+
+if os.name == "posix":
+    import termios
+    def i_should_be_followed_by_only_one_newline():
+        pass
+elif os.name == "nt":
+    try:
+        import msvcrt
+        def i_should_be_followed_by_only_one_newline():
+            pass
+
+    except ImportError:
+
+        def i_should_be_followed_by_only_one_newline():
+            pass
+
+elif False:
+
+    class IHopeYouAreHavingALovelyDay:
+        def __call__(self):
+            print("i_should_be_followed_by_only_one_newline")
+else:
+
+    def foo():
+        pass
+
+with hmm_but_this_should_get_two_preceding_newlines():
+    pass
+```
+
+## Black Differences
+
+```diff
+--- Black
++++ Ruff
+@@ -36,7 +36,6 @@
+ 
+     def i_should_be_followed_by_only_one_newline():
+         pass
+-
+ elif os.name == "nt":
+     try:
+         import msvcrt
+```
+
+## Ruff Output
+
+```python
+def f(
+    a,
+    **kwargs,
+) -> A:
+    with cache_dir():
+        if something:
+            result = CliRunner().invoke(
+                black.main, [str(src1), str(src2), "--diff", "--check"]
+            )
+    limited.append(-limited.pop())  # negate top
+    return A(
+        very_long_argument_name1=very_long_value_for_the_argument,
+        very_long_argument_name2=-very.long.value.for_the_argument,
+        **kwargs,
+    )
+
+
+def g():
+    "Docstring."
+
+    def inner():
+        pass
+
+    print("Inner defs should breathe a little.")
+
+
+def h():
+    def inner():
+        pass
+
+    print("Inner defs should breathe a little.")
+
+
+if os.name == "posix":
+    import termios
+
+    def i_should_be_followed_by_only_one_newline():
+        pass
+elif os.name == "nt":
+    try:
+        import msvcrt
+
+        def i_should_be_followed_by_only_one_newline():
+            pass
+
+    except ImportError:
+
+        def i_should_be_followed_by_only_one_newline():
+            pass
+
+elif False:
+
+    class IHopeYouAreHavingALovelyDay:
+        def __call__(self):
+            print("i_should_be_followed_by_only_one_newline")
+
+else:
+
+    def foo():
+        pass
+
+
+with hmm_but_this_should_get_two_preceding_newlines():
+    pass
+```
+
+## Black Output
+
+```python
+def f(
+    a,
+    **kwargs,
+) -> A:
+    with cache_dir():
+        if something:
+            result = CliRunner().invoke(
+                black.main, [str(src1), str(src2), "--diff", "--check"]
+            )
+    limited.append(-limited.pop())  # negate top
+    return A(
+        very_long_argument_name1=very_long_value_for_the_argument,
+        very_long_argument_name2=-very.long.value.for_the_argument,
+        **kwargs,
+    )
+
+
+def g():
+    "Docstring."
+
+    def inner():
+        pass
+
+    print("Inner defs should breathe a little.")
+
+
+def h():
+    def inner():
+        pass
+
+    print("Inner defs should breathe a little.")
+
+
+if os.name == "posix":
+    import termios
+
+    def i_should_be_followed_by_only_one_newline():
+        pass
+
+elif os.name == "nt":
+    try:
+        import msvcrt
+
+        def i_should_be_followed_by_only_one_newline():
+            pass
+
+    except ImportError:
+
+        def i_should_be_followed_by_only_one_newline():
+            pass
+
+elif False:
+
+    class IHopeYouAreHavingALovelyDay:
+        def __call__(self):
+            print("i_should_be_followed_by_only_one_newline")
+
+else:
+
+    def foo():
+        pass
+
+
+with hmm_but_this_should_get_two_preceding_newlines():
+    pass
+```

crates/ruff_python_formatter/tests/snapshots/format@newlines.py.snap

@@ -616,7 +616,6 @@ if True:
 
     def a():
         return 1
-
 else:
     pass
 
@@ -625,7 +624,6 @@ match True:
 
         def a():
             return 1
-
     case 1:
 
         def a():
@@ -636,7 +634,6 @@ try:
 
     def a():
         return 1
-
 except RuntimeError:
 
     def a():
@@ -647,7 +644,6 @@ try:
 
     def a():
         return 1
-
 finally:
 
     def a():
@@ -658,22 +654,18 @@ try:
 
     def a():
         return 1
-
 except RuntimeError:
 
     def a():
         return 1
-
 except ZeroDivisionError:
 
     def a():
         return 1
-
 else:
 
     def a():
         return 1
-
 finally:
 
     def a():
@@ -724,3 +716,65 @@ def overload4():
 
 def overload4(a: int): ...
 ```
+
+
+## Preview changes
+```diff
+--- Stable
++++ Preview
+@@ -277,6 +277,7 @@
+ 
+     def a():
+         return 1
++
+ else:
+     pass
+ 
+@@ -285,6 +286,7 @@
+ 
+         def a():
+             return 1
++
+     case 1:
+ 
+         def a():
+@@ -295,6 +297,7 @@
+ 
+     def a():
+         return 1
++
+ except RuntimeError:
+ 
+     def a():
+@@ -305,6 +308,7 @@
+ 
+     def a():
+         return 1
++
+ finally:
+ 
+     def a():
+@@ -315,18 +319,22 @@
+ 
+     def a():
+         return 1
++
+ except RuntimeError:
+ 
+     def a():
+         return 1
++
+ except ZeroDivisionError:
+ 
+     def a():
+         return 1
++
+ else:
+ 
+     def a():
+         return 1
++
+ finally:
+ 
+     def a():
+```