Format Attribute Expression (#5259)

crates/ruff_python_formatter/src/expression/expr_attribute.rs

@@ -1,9 +1,9 @@
-use crate::comments::Comments;
+use crate::comments::{leading_comments, trailing_comments, Comments};
 use crate::expression::parentheses::{
     default_expression_needs_parentheses, NeedsParentheses, Parentheses, Parenthesize,
 };
 use crate::prelude::*;
-use crate::{not_yet_implemented_custom_text, FormatNodeRule};
+use crate::FormatNodeRule;
 use ruff_formatter::write;
 use rustpython_parser::ast::{Constant, Expr, ExprAttribute, ExprConstant};
 
@@ -15,11 +15,11 @@ impl FormatNodeRule<ExprAttribute> for FormatExprAttribute {
         let ExprAttribute {
             value,
             range: _,
-            attr: _,
+            attr,
             ctx: _,
         } = item;
 
-        let requires_space = matches!(
+        let needs_parentheses = matches!(
             value.as_ref(),
             Expr::Constant(ExprConstant {
                 value: Constant::Int(_) | Constant::Float(_),
@@ -27,16 +27,45 @@ impl FormatNodeRule<ExprAttribute> for FormatExprAttribute {
             })
         );
 
+        if needs_parentheses {
+            value.format().with_options(Parenthesize::Always).fmt(f)?;
+        } else {
+            value.format().fmt(f)?;
+        }
+
+        let comments = f.context().comments().clone();
+
+        if comments.has_trailing_own_line_comments(value.as_ref()) {
+            hard_line_break().fmt(f)?;
+        }
+
+        let dangling_comments = comments.dangling_comments(item);
+
+        let leading_attribute_comments_start =
+            dangling_comments.partition_point(|comment| comment.line_position().is_end_of_line());
+        let (trailing_dot_comments, leading_attribute_comments) =
+            dangling_comments.split_at(leading_attribute_comments_start);
+
         write!(
             f,
             [
-                item.value.format(),
-                requires_space.then_some(space()),
                 text("."),
-                not_yet_implemented_custom_text("NOT_IMPLEMENTED_attr")
+                trailing_comments(trailing_dot_comments),
+                (!leading_attribute_comments.is_empty()).then_some(hard_line_break()),
+                leading_comments(leading_attribute_comments),
+                attr.format()
             ]
         )
     }
+
+    fn fmt_dangling_comments(
+        &self,
+        _node: &ExprAttribute,
+        _f: &mut PyFormatter,
+    ) -> FormatResult<()> {
+        // handle in `fmt_fields`
+        Ok(())
+    }
 }
 
 impl NeedsParentheses for ExprAttribute {
@@ -46,6 +75,9 @@ impl NeedsParentheses for ExprAttribute {
         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 => Parentheses::Never,
+            parentheses => parentheses,
+        }
     }
 }