Format UnaryExpr

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## Summary

This PR adds basic formatting for unary expressions.

<!-- What's the purpose of the change? What does it do, and why? -->

## Test Plan

I added a new `unary.py` with custom test cases

crates/ruff_python_formatter/src/expression/expr_bin_op.rs

@@ -323,6 +323,10 @@ fn can_break(expr: &Expr) -> bool {
         }) => !expressions.is_empty(),
         Expr::Call(ExprCall { args, keywords, .. }) => !(args.is_empty() && keywords.is_empty()),
         Expr::ListComp(_) | Expr::SetComp(_) | Expr::DictComp(_) | Expr::GeneratorExp(_) => true,
+        Expr::UnaryOp(ExprUnaryOp { operand, .. }) => match operand.as_ref() {
+            Expr::BinOp(_) => true,
+            _ => can_break(operand.as_ref()),
+        },
         _ => false,
     }
 }

crates/ruff_python_formatter/src/expression/expr_unary_op.rs

@@ -1,17 +1,68 @@
-use crate::comments::Comments;
+use crate::comments::{trailing_comments, Comments};
 use crate::expression::parentheses::{
     default_expression_needs_parentheses, NeedsParentheses, Parentheses, Parenthesize,
 };
-use crate::{not_yet_implemented, FormatNodeRule, PyFormatter};
-use ruff_formatter::{write, Buffer, FormatResult};
-use rustpython_parser::ast::ExprUnaryOp;
+use crate::prelude::*;
+use crate::trivia::{SimpleTokenizer, TokenKind};
+use crate::FormatNodeRule;
+use ruff_formatter::FormatContext;
+use ruff_python_ast::prelude::UnaryOp;
+use ruff_text_size::{TextLen, TextRange};
+use rustpython_parser::ast::{ExprUnaryOp, Ranged};
 
 #[derive(Default)]
 pub struct FormatExprUnaryOp;
 
 impl FormatNodeRule<ExprUnaryOp> for FormatExprUnaryOp {
     fn fmt_fields(&self, item: &ExprUnaryOp, f: &mut PyFormatter) -> FormatResult<()> {
-        write!(f, [not_yet_implemented(item)])
+        let ExprUnaryOp {
+            range: _,
+            op,
+            operand,
+        } = item;
+
+        let operator = match op {
+            UnaryOp::Invert => "~",
+            UnaryOp::Not => "not",
+            UnaryOp::UAdd => "+",
+            UnaryOp::USub => "-",
+        };
+
+        text(operator).fmt(f)?;
+
+        let comments = f.context().comments().clone();
+
+        // Split off the comments that follow after the operator and format them as trailing comments.
+        // ```python
+        // (not # comment
+        //      a)
+        // ```
+        let leading_operand_comments = comments.leading_comments(operand.as_ref());
+        let trailing_operator_comments_end =
+            leading_operand_comments.partition_point(|p| p.position().is_end_of_line());
+        let (trailing_operator_comments, leading_operand_comments) =
+            leading_operand_comments.split_at(trailing_operator_comments_end);
+
+        if !trailing_operator_comments.is_empty() {
+            trailing_comments(trailing_operator_comments).fmt(f)?;
+        }
+
+        // Insert a line break if the operand has comments but itself is not parenthesized.
+        // ```python
+        // if (
+        //  not
+        //  # comment
+        //  a)
+        // ```
+        if !leading_operand_comments.is_empty()
+            && !is_operand_parenthesized(item, f.context().source_code().as_str())
+        {
+            hard_line_break().fmt(f)?;
+        } else if op.is_not() {
+            space().fmt(f)?;
+        }
+
+        operand.format().fmt(f)
     }
 }
 
@@ -22,6 +73,37 @@ impl NeedsParentheses for ExprUnaryOp {
         source: &str,
         comments: &Comments,
     ) -> Parentheses {
-        default_expression_needs_parentheses(self.into(), parenthesize, source, comments)
+        match default_expression_needs_parentheses(self.into(), parenthesize, source, comments) {
+            Parentheses::Optional => {
+                // We preserve the parentheses of the operand. It should not be necessary to break this expression.
+                if is_operand_parenthesized(self, source) {
+                    Parentheses::Never
+                } else {
+                    Parentheses::Optional
+                }
+            }
+            parentheses => parentheses,
+        }
+    }
+}
+
+fn is_operand_parenthesized(unary: &ExprUnaryOp, source: &str) -> bool {
+    let operator_len = match unary.op {
+        UnaryOp::Invert => '~'.text_len(),
+        UnaryOp::Not => "not".text_len(),
+        UnaryOp::UAdd => '+'.text_len(),
+        UnaryOp::USub => '-'.text_len(),
+    };
+
+    let trivia_range = TextRange::new(unary.range.start() + operator_len, unary.operand.start());
+
+    if let Some(token) = SimpleTokenizer::new(source, trivia_range)
+        .skip_trivia()
+        .next()
+    {
+        debug_assert_eq!(token.kind(), TokenKind::LParen);
+        true
+    } else {
+        false
     }
 }

crates/ruff_python_formatter/src/expression/parentheses.rs

@@ -42,7 +42,7 @@ pub(super) fn default_expression_needs_parentheses(
 }
 
 /// Configures if the expression should be parenthesized.
-#[derive(Copy, Clone, Debug, Default)]
+#[derive(Copy, Clone, Debug, Default, Eq, PartialEq)]
 pub enum Parenthesize {
     /// Parenthesize the expression if it has parenthesis in the source.
     #[default]
@@ -56,11 +56,11 @@ pub enum Parenthesize {
 }
 
 impl Parenthesize {
-    const fn is_if_breaks(self) -> bool {
+    pub(crate) const fn is_if_breaks(self) -> bool {
         matches!(self, Parenthesize::IfBreaks)
     }
 
-    const fn is_preserve(self) -> bool {
+    pub(crate) const fn is_preserve(self) -> bool {
         matches!(self, Parenthesize::Preserve)
     }
 }