Indent lambda parameters if parameters wrap

crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/lambda.py

@@ -203,3 +203,5 @@ def f(
     y:
     z
 )
+
+lambda self, araa, kkkwargs=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(*args, **kwargs), e=1, f=2, g=2: d

crates/ruff_python_formatter/src/comments/placement.rs

@@ -1805,18 +1805,6 @@ fn handle_lambda_comment<'a>(
     locator: &Locator,
 ) -> CommentPlacement<'a> {
     if let Some(parameters) = lambda.parameters.as_deref() {
-        // Comments between the `lambda` and the parameters are dangling on the lambda:
-        // ```python
-        // (
-        //     lambda  # comment
-        //     x:
-        //     y
-        // )
-        // ```
-        if comment.start() < parameters.start() {
-            return CommentPlacement::dangling(comment.enclosing_node(), comment);
-        }
-
         // Comments between the parameters and the body are dangling on the lambda:
         // ```python
         // (

crates/ruff_python_formatter/src/expression/expr_lambda.rs

@@ -3,8 +3,10 @@ use ruff_python_ast::AnyNodeRef;
 use ruff_python_ast::ExprLambda;
 use ruff_text_size::Ranged;
 
+use crate::builders::parenthesize_if_expands;
 use crate::comments::{dangling_comments, SourceComment};
-use crate::expression::parentheses::{NeedsParentheses, OptionalParentheses};
+use crate::expression::has_own_parentheses;
+use crate::expression::parentheses::{NeedsParentheses, OptionalParentheses, Parentheses};
 use crate::other::parameters::ParametersParentheses;
 use crate::prelude::*;
 
@@ -25,7 +27,7 @@ impl FormatNodeRule<ExprLambda> for FormatExprLambda {
         write!(f, [token("lambda")])?;
 
         if let Some(parameters) = parameters {
-            // In this context, a dangling comment can either be a comment between the `lambda` the
+            // In this context, a dangling comment can either be a comment between the `lambda` and the
             // parameters, or a comment between the parameters and the body.
             let (dangling_before_parameters, dangling_after_parameters) = dangling
                 .split_at(dangling.partition_point(|comment| comment.end() < parameters.start()));
@@ -36,20 +38,30 @@ impl FormatNodeRule<ExprLambda> for FormatExprLambda {
                 write!(f, [dangling_comments(dangling_before_parameters)])?;
             }
 
-            write!(
-                f,
-                [parameters
-                    .format()
-                    .with_options(ParametersParentheses::Never)]
-            )?;
+            group(&format_with(|f: &mut PyFormatter| {
+                if f.context().node_level().is_parenthesized() {
+                    soft_block_indent(
+                        &parameters
+                            .format()
+                            .with_options(ParametersParentheses::Never),
+                    )
+                    .fmt(f)
+                } else {
+                    parameters
+                        .format()
+                        .with_options(ParametersParentheses::Never)
+                        .fmt(f)
+                }?;
 
-            write!(f, [token(":")])?;
+                token(":").fmt(f)?;
 
-            if dangling_after_parameters.is_empty() {
-                write!(f, [space()])?;
-            } else {
-                write!(f, [dangling_comments(dangling_after_parameters)])?;
-            }
+                if dangling_after_parameters.is_empty() {
+                    space().fmt(f)
+                } else {
+                    dangling_comments(dangling_after_parameters).fmt(f)
+                }
+            }))
+            .fmt(f)?;
         } else {
             write!(f, [token(":")])?;
 
@@ -61,7 +73,13 @@ impl FormatNodeRule<ExprLambda> for FormatExprLambda {
             }
         }
 
-        write!(f, [body.format()])
+        if has_own_parentheses(body, f.context()).is_some()
+            || body.needs_parentheses(item.into(), f.context()) == OptionalParentheses::Always
+        {
+            body.format().fmt(f)
+        } else {
+            parenthesize_if_expands(&body.format().with_options(Parentheses::Never)).fmt(f)
+        }
     }
 
     fn fmt_dangling_comments(

crates/ruff_python_formatter/src/expression/expr_named_expr.rs

@@ -69,6 +69,7 @@ impl NeedsParentheses for ExprNamedExpr {
             || parent.is_stmt_delete()
             || parent.is_stmt_for()
             || parent.is_stmt_function_def()
+            || parent.is_expr_lambda()
         {
             OptionalParentheses::Always
         } else {

crates/ruff_python_formatter/src/lib.rs

@@ -206,14 +206,7 @@ if True:
     #[test]
     fn quick_test() {
         let source = r#"
-def main() -> None:
-    if True:
-        some_very_long_variable_name_abcdefghijk = Foo()
-        some_very_long_variable_name_abcdefghijk = some_very_long_variable_name_abcdefghijk[
-            some_very_long_variable_name_abcdefghijk.some_very_long_attribute_name
-            == "This is a very long string abcdefghijk"
-        ]
-
+lambda self, araa, kkkwargs=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(*args, **kwargs), e=1, f=2, g=2: d
 "#;
         let source_type = PySourceType::Python;
         let (tokens, comment_ranges) = tokens_and_ranges(source, source_type).unwrap();

crates/ruff_python_formatter/src/other/parameters.rs

@@ -102,7 +102,15 @@ impl FormatNodeRule<Parameters> for FormatParameters {
             dangling.split_at(parenthesis_comments_end);
 
         let format_inner = format_with(|f: &mut PyFormatter| {
-            let separator = format_with(|f| write!(f, [token(","), soft_line_break_or_space()]));
+            let separator = format_with(|f: &mut PyFormatter| {
+                token(",").fmt(f)?;
+
+                if f.context().node_level().is_parenthesized() {
+                    soft_line_break_or_space().fmt(f)
+                } else {
+                    space().fmt(f)
+                }
+            });
             let mut joiner = f.join_with(separator);
             let mut last_node: Option<AnyNodeRef> = None;
 
@@ -232,20 +240,21 @@ impl FormatNodeRule<Parameters> for FormatParameters {
             Ok(())
         });
 
-        let mut f = WithNodeLevel::new(NodeLevel::ParenthesizedExpression, f);
-
         let num_parameters = posonlyargs.len()
             + args.len()
             + usize::from(vararg.is_some())
             + kwonlyargs.len()
             + usize::from(kwarg.is_some());
 
         if self.parentheses == ParametersParentheses::Never {
-            write!(f, [group(&format_inner), dangling_comments(dangling)])
+            write!(f, [format_inner, dangling_comments(dangling)])
         } else if num_parameters == 0 {
+            let mut f = WithNodeLevel::new(NodeLevel::ParenthesizedExpression, f);
             // No parameters, format any dangling comments between `()`
             write!(f, [empty_parenthesized("(", dangling, ")")])
         } else {
+            let mut f = WithNodeLevel::new(NodeLevel::ParenthesizedExpression, f);
+
             // Intentionally avoid `parenthesized`, which groups the entire formatted contents.
             // We want parameters to be grouped alongside return types, one level up, so we
             // format them "inline" here.

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

@@ -209,6 +209,8 @@ lambda: ( # comment
     y:
     z
 )
+
+lambda self, araa, kkkwargs=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(*args, **kwargs), e=1, f=2, g=2: d
 ```
 
 ## Output
@@ -242,30 +244,10 @@ lambda x: lambda y: lambda z: (x, y, z)  # Trailing
 # Trailing
 
 # Leading
-lambda x: lambda y: lambda z: (
-    x,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    y,
-    z,
+lambda x: (
+    lambda y: (
+        lambda z: (x, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, y, z)
+    )
 )  # Trailing
 # Trailing
 
@@ -275,8 +257,10 @@ a = (
 )
 
 a = (
-    lambda x,  # Dangling
-    y: 1
+    lambda 
+        x,  # Dangling
+        y
+    : 1
 )
 
 # Regression test: lambda empty arguments ranges were too long, leading to unstable
@@ -289,7 +273,9 @@ a = (
 
 # lambda arguments don't have parentheses, so we never add a magic trailing comma ...
 def f(
-    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb = lambda x: y,
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa: bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb = lambda 
+        x
+    : y,
 ):
     pass
 
@@ -336,36 +322,42 @@ lambda a, /, c: a
 )
 
 (
-    lambda
-    # comment
-    *x: x
+    lambda 
+        # comment
+        *x
+    : x
 )
 
 (
-    lambda
-    # comment 1
-    # comment 2
-    *x:
+    lambda 
+        # comment 1
+        # comment 2
+        *x
+    :
     # comment 3
     x
 )
 
 (
-    lambda  # comment 1
-    # comment 2
-    *x:  # comment 3
+    lambda 
+        # comment 1
+        # comment 2
+        *x
+    :  # comment 3
     x
 )
 
 lambda *x: x
 
 (
-    lambda
-    # comment
-    *x: x
+    lambda 
+        # comment
+        *x
+    : x
 )
 
-lambda: (  # comment
+lambda: (
+    # comment
     x
 )
 
@@ -393,26 +385,35 @@ lambda: (  # comment
 
 (
     lambda:  # comment
-    (  # comment
+    (
+        # comment
         x
     )
 )
 
 (
-    lambda  # 1
-    # 2
-    x:  # 3
+    lambda 
+        # 1
+        # 2
+        x
+    :  # 3
     # 4
     # 5
     # 6
     x
 )
 
 (
-    lambda x,
-    # comment
-    y: z
+    lambda 
+        x,
+        # comment
+        y
+    : z
 )
+
+lambda self, araa, kkkwargs=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa(
+    *args, **kwargs
+), e=1, f=2, g=2: d
 ```