Fix panic when formatting comments in unary expressions (#21501)

## Summary

This is another attempt at https://github.com/astral-sh/ruff/pull/21410
that fixes https://github.com/astral-sh/ruff/issues/19226.

@MichaReiser helped me get something working in a very helpful pairing
session. I pushed one additional commit moving the comments back from
leading comments to trailing comments, which I think retains more of the
input formatting.

I was inspired by Dylan's PR (#21185) to make one of these tables:

<table>
                <thead>
                    <tr>
                    <th scope="col">Input</th>
                    <th scope="col">Main</th>
                    <th scope="col">PR</th>
                    </tr>
                </thead>
                <tbody>
<tr>
<td><pre lang="python">
if (
    not
    # comment
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa +
bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass
</pre></td>
<td><pre lang="python">
if (
    # comment
    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
<td><pre lang="python">
if (
    not
    # comment
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
</tr>
<tr>
<td><pre lang="python">
if (
    # unary comment
    not
    # operand comment
    (
        # comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    )
):
    pass
</pre></td>
<td><pre lang="python">
if (
    # unary comment
    # operand comment
    not (
        # comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    )
):
    pass

</pre></td>
<td><pre lang="python">
if (
    # unary comment
    not
    # operand comment
    (
        # comment
        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
        + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
    )
):
    pass

</pre></td>
</tr>
<tr>
<td><pre lang="python">
if (
    not # comment
    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass
</pre></td>
<td><pre lang="python">
if (  # comment
    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
<td><pre lang="python">
if (
    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  # comment
    + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
):
    pass

</pre></td>
</tr>
</tbody>
            </table>

hopefully it helps even though the snippets are much wider here.

The two main differences are (1) that we now retain own-line comments
between the unary operator and its operand instead of moving these to
leading comments on the operator itself, and (2) that we move
end-of-line comments between the operator and operand to dangling
end-of-line comments on the operand (the last example in the table).

## Test Plan

Existing tests, plus new ones based on the issue. As I noted below, I
also ran the output from main on the unary.py file back through this
branch to check that we don't reformat code from main. This made me feel
a bit better about not preview-gating the changes in this PR.

```shell
> git show main:crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/unary.py | ruff format - | ./target/debug/ruff format --diff -
> echo $?
0
```

---------

Co-authored-by: Micha Reiser <micha@reiser.io>
Co-authored-by: Takayuki Maeda <takoyaki0316@gmail.com>

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

@@ -193,3 +193,58 @@ def foo():
         not (aaaaaaaaaaaaaaaaaaaaa[bbbbbbbb, ccccccc]) and dddddddddd < eeeeeeeeeeeeeee
     ):
         pass
+
+# Regression tests for https://github.com/astral-sh/ruff/issues/19226
+if '' and (not #
+0):
+    pass
+
+if '' and (not #
+(0)
+):
+    pass
+
+if '' and (not
+	(  #
+	0
+)):
+    pass
+
+if (
+  not
+  # comment
+  (a)):
+    pass
+
+if not ( # comment
+      a):
+    pass
+
+if not (
+  # comment
+  (a)):
+    pass
+
+if not (
+  # comment
+  a):
+    pass
+
+not (# comment
+  (a))
+
+(-#comment
+ (a))
+
+if ( # a
+        # b
+  not # c
+  # d
+  ( # e
+      # f
+      a # g
+      # h
+  ) # i
+  # j
+):
+    pass

crates/ruff_python_formatter/src/comments/placement.rs

@@ -1890,9 +1890,11 @@ fn handle_lambda_comment<'a>(
     CommentPlacement::Default(comment)
 }
 
-/// Move comment between a unary op and its operand before the unary op by marking them as trailing.
+/// Move an end-of-line comment between a unary op and its operand after the operand by marking
+/// it as dangling.
 ///
 /// For example, given:
+///
 /// ```python
 /// (
 ///     not  # comment
@@ -1900,8 +1902,13 @@ fn handle_lambda_comment<'a>(
 /// )
 /// ```
 ///
-/// The `# comment` will be attached as a dangling comment on the enclosing node, to ensure that
+/// the `# comment` will be attached as a dangling comment on the unary op and formatted as:
-/// it remains on the same line as the operator.
+///
+/// ```python
+/// (
+///      not True  # comment
+/// )
+/// ```
 fn handle_unary_op_comment<'a>(
     comment: DecoratedComment<'a>,
     unary_op: &'a ast::ExprUnaryOp,
@@ -1923,8 +1930,8 @@ fn handle_unary_op_comment<'a>(
     let up_to = tokenizer
         .find(|token| token.kind == SimpleTokenKind::LParen)
         .map_or(unary_op.operand.start(), |lparen| lparen.start());
-    if comment.end() < up_to {
+    if comment.end() < up_to && comment.line_position().is_end_of_line() {
-        CommentPlacement::leading(unary_op, comment)
+        CommentPlacement::dangling(unary_op, comment)
     } else {
         CommentPlacement::Default(comment)
     }

crates/ruff_python_formatter/src/expression/expr_unary_op.rs

@@ -1,6 +1,8 @@
 use ruff_python_ast::AnyNodeRef;
 use ruff_python_ast::ExprUnaryOp;
 use ruff_python_ast::UnaryOp;
+use ruff_python_ast::parenthesize::parenthesized_range;
+use ruff_text_size::Ranged;
 
 use crate::comments::trailing_comments;
 use crate::expression::parentheses::{
@@ -39,20 +41,25 @@ impl FormatNodeRule<ExprUnaryOp> for FormatExprUnaryOp {
         // ```
         trailing_comments(dangling).fmt(f)?;
 
-        // Insert a line break if the operand has comments but itself is not parenthesized.
+        // Insert a line break if the operand has comments but itself is not parenthesized or if the
+        // operand is parenthesized but has a leading comment before the parentheses.
         // ```python
         // if (
         //  not
         //  # comment
-        //  a)
+        //  a):
+        //      pass
+        //
+        // if 1 and (
+        //     not
+        //     # comment
+        //     (
+        //         a
+        //     )
+        // ):
+        //     pass
         // ```
-        if comments.has_leading(operand.as_ref())
+        if needs_line_break(item, f.context()) {
-            && !is_expression_parenthesized(
-                operand.as_ref().into(),
-                f.context().comments().ranges(),
-                f.context().source(),
-            )
-        {
             hard_line_break().fmt(f)?;
         } else if op.is_not() {
             space().fmt(f)?;
@@ -76,17 +83,51 @@ impl NeedsParentheses for ExprUnaryOp {
         context: &PyFormatContext,
     ) -> OptionalParentheses {
         if parent.is_expr_await() {
-            OptionalParentheses::Always
+            return OptionalParentheses::Always;
-        } else if is_expression_parenthesized(
+        }
+
+        if needs_line_break(self, context) {
+            return OptionalParentheses::Always;
+        }
+
+        if is_expression_parenthesized(
             self.operand.as_ref().into(),
             context.comments().ranges(),
             context.source(),
         ) {
-            OptionalParentheses::Never
+            return OptionalParentheses::Never;
-        } else if context.comments().has(self.operand.as_ref()) {
+        }
-            OptionalParentheses::Always
+
-        } else {
+        if context.comments().has(self.operand.as_ref()) {
+            return OptionalParentheses::Always;
+        }
+
         self.operand.needs_parentheses(self.into(), context)
     }
 }
+
+/// Returns `true` if the unary operator will have a hard line break between the operator and its
+/// operand and thus requires parentheses.
+fn needs_line_break(item: &ExprUnaryOp, context: &PyFormatContext) -> bool {
+    let comments = context.comments();
+    let parenthesized_operand_range = parenthesized_range(
+        item.operand.as_ref().into(),
+        item.into(),
+        comments.ranges(),
+        context.source(),
+    );
+    let leading_operand_comments = comments.leading(item.operand.as_ref());
+    let has_leading_comments_before_parens = parenthesized_operand_range.is_some_and(|range| {
+        leading_operand_comments
+            .iter()
+            .any(|comment| comment.start() < range.start())
+    });
+
+    !leading_operand_comments.is_empty()
+        && !is_expression_parenthesized(
+            item.operand.as_ref().into(),
+            context.comments().ranges(),
+            context.source(),
+        )
+        || has_leading_comments_before_parens
 }

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

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_formatter/tests/fixtures.rs
 input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/expression/unary.py
-snapshot_kind: text
 ---
 ## Input
 ```python
@@ -200,6 +199,61 @@ def foo():
         not (aaaaaaaaaaaaaaaaaaaaa[bbbbbbbb, ccccccc]) and dddddddddd < eeeeeeeeeeeeeee
     ):
         pass
+
+# Regression tests for https://github.com/astral-sh/ruff/issues/19226
+if '' and (not #
+0):
+    pass
+
+if '' and (not #
+(0)
+):
+    pass
+
+if '' and (not
+	(  #
+	0
+)):
+    pass
+
+if (
+  not
+  # comment
+  (a)):
+    pass
+
+if not ( # comment
+      a):
+    pass
+
+if not (
+  # comment
+  (a)):
+    pass
+
+if not (
+  # comment
+  a):
+    pass
+
+not (# comment
+  (a))
+
+(-#comment
+ (a))
+
+if ( # a
+        # b
+  not # c
+  # d
+  ( # e
+      # f
+      a # g
+      # h
+  ) # i
+  # j
+):
+    pass
 ```
 
 ## Output
@@ -250,31 +304,35 @@ if +(
     pass
 
 if (
+    not
     # comment
-    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
 
 
 if (
+    ~
     # comment
-    ~aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
 
 if (
+    -
     # comment
-    -aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
 
 
 if (
+    +
     # comment
-    +aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
@@ -283,8 +341,9 @@ if (
 
 if (
     # unary comment
+    not
     # operand comment
-    not (
+    (
         # comment
         aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
         + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
@@ -318,31 +377,28 @@ if (
 
 ## Trailing operator comments
 
-if (  # comment
+if (
-    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+    not aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  # comment
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
 
 
 if (
-    # comment
+    ~aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  # comment
-    ~aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
 
 if (
-    # comment
+    -aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  # comment
-    -aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
 
 
 if (
-    # comment
+    +aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa  # comment
-    +aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
     + bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
 ):
     pass
@@ -362,14 +418,13 @@ if (
     pass
 
 if (
+    not
     # comment
-    not a
+    a
 ):
     pass
 
-if (  # comment
+if not a:  # comment
-    not a
-):
     pass
 
 # Regression test for: https://github.com/astral-sh/ruff/issues/7423
@@ -385,9 +440,9 @@ if True:
 # Regression test for: https://github.com/astral-sh/ruff/issues/7448
 x = (
     # a
-    # b
+    not  # b
     # c
-    not (  # d
+    (  # d
         # e
         True
     )
@@ -415,4 +470,68 @@ def foo():
         not (aaaaaaaaaaaaaaaaaaaaa[bbbbbbbb, ccccccc]) and dddddddddd < eeeeeeeeeeeeeee
     ):
         pass
+
+
+# Regression tests for https://github.com/astral-sh/ruff/issues/19226
+if "" and (
+    not 0  #
+):
+    pass
+
+if "" and (
+    not (0)  #
+):
+    pass
+
+if "" and (
+    not (  #
+        0
+    )
+):
+    pass
+
+if (
+    not
+    # comment
+    (a)
+):
+    pass
+
+if not (  # comment
+    a
+):
+    pass
+
+if not (
+    # comment
+    a
+):
+    pass
+
+if not (
+    # comment
+    a
+):
+    pass
+
+not (  # comment
+    a
+)
+
+(
+    -(a)  # comment
+)
+
+if (  # a
+    # b
+    not  # c
+    # d
+    (  # e
+        # f
+        a  # g
+        # h
+    )  # i
+    # j
+):
+    pass
 ```

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

@@ -1,7 +1,6 @@
 ---
 source: crates/ruff_python_formatter/tests/fixtures.rs
 input_file: crates/ruff_python_formatter/resources/test/fixtures/ruff/parentheses/expression_parentheses_comments.py
-snapshot_kind: text
 ---
 ## Input
 ```python
@@ -179,13 +178,13 @@ nested_parentheses4 = [
 
 x = (
     # unary comment
+    not
     # in-between comment
-    not (
+    (
         # leading inner
         "a"
     ),
-    # in-between comment
+    not (  # in-between comment
-    not (
         # leading inner
         "b"
     ),
@@ -194,8 +193,7 @@ x = (
         "c"
     ),
     # 1
-    # 2
+    not (  # 2  # 3
-    not (  # 3
         # 4
         "d"
     ),
@@ -203,8 +201,9 @@ x = (
 
 if (
     # unary comment
+    not
     # in-between comment
-    not (
+    (
         # leading inner
         1
     )