challenge(formatter): arrows comment

crates/biome_js_formatter/src/comments.rs

@@ -14,8 +14,9 @@ use biome_js_syntax::JsSyntaxKind::JS_EXPORT;
 use biome_js_syntax::{
     AnyJsClass, AnyJsName, AnyJsRoot, AnyJsStatement, JsArrayHole, JsArrowFunctionExpression,
     JsBlockStatement, JsCallArguments, JsCatchClause, JsEmptyStatement, JsFinallyClause,
-    JsFormalParameter, JsFunctionBody, JsIdentifierExpression, JsIfStatement, JsLanguage,
-    JsSyntaxKind, JsSyntaxNode, JsVariableDeclarator, JsWhileStatement, TsInterfaceDeclaration,
+    JsFormalParameter, JsFunctionBody, JsIdentifierBinding, JsIdentifierExpression, JsIfStatement,
+    JsLanguage, JsParameters, JsSyntaxKind, JsSyntaxNode, JsVariableDeclarator, JsWhileStatement,
+    TsInterfaceDeclaration,
 };
 use biome_rowan::{AstNode, SyntaxNodeOptionExt, SyntaxTriviaPieceComments, TextLen};
 
@@ -116,6 +117,7 @@ impl CommentStyle for JsCommentStyle {
                 .or_else(handle_continue_break_comment)
                 .or_else(handle_mapped_type_comment)
                 .or_else(handle_switch_default_case_comment)
+                .or_else(handle_after_arrow_fat_arrow_comment)
                 .or_else(handle_import_export_specifier_comment),
             CommentTextPosition::OwnLine => handle_member_expression_comment(comment)
                 .or_else(handle_function_declaration_comment)
@@ -157,6 +159,63 @@ fn handle_typecast_comment(comment: DecoratedComment<JsLanguage>) -> CommentPlac
     }
 }
 
+/// Move the arrow function's comment to the same position as the prettier
+fn handle_after_arrow_fat_arrow_comment(
+    comment: DecoratedComment<JsLanguage>,
+) -> CommentPlacement<JsLanguage> {
+    if JsArrowFunctionExpression::can_cast(comment.enclosing_node().kind()) {
+        // input
+        // ```javascript
+        // num => // comment
+        // c;
+        // ```
+        // output
+        // ```javascript
+        //(
+        //   num, // comment
+        // ) => c;
+        // ```
+        if let Some(js_ident_binding) = comment
+            .preceding_node()
+            .and_then(JsIdentifierBinding::cast_ref)
+        {
+            return CommentPlacement::trailing(js_ident_binding.into_syntax(), comment);
+        }
+        // input
+        // ```javascript
+        // (num1,num2) => // comment
+        // c;
+        // ```
+        // output
+        // ```javascript
+        // (
+        //     num1,
+        //     num2, // comment
+        //  ) => c;
+        // ```
+        if let Some(js_parameters) = comment.preceding_node().and_then(JsParameters::cast_ref) {
+            if let Some(Ok(last)) = js_parameters.items().last() {
+                return CommentPlacement::trailing(last.into_syntax(), comment);
+            };
+        }
+        // input
+        // ```javascript
+        // () => // comment
+        // c;
+        // ```
+        // output
+        // ```javascript
+        // () =>
+        // // comment
+        // c;
+        // ```
+        if let Some(following_node) = comment.following_node() {
+            return CommentPlacement::leading(following_node.clone(), comment);
+        }
+    }
+    CommentPlacement::Default(comment)
+}
+
 fn handle_after_arrow_param_comment(
     comment: DecoratedComment<JsLanguage>,
 ) -> CommentPlacement<JsLanguage> {

crates/biome_js_formatter/src/js/expressions/arrow_function_expression.rs

@@ -102,7 +102,22 @@ impl FormatNodeRule<JsArrowFunctionExpression> for FormatJsArrowFunctionExpressi
                     AnyJsExpression(JsTemplateExpression(template)) => {
                         is_multiline_template_starting_on_same_line(template)
                     }
-                    AnyJsExpression(JsSequenceExpression(_)) => {
+                    AnyJsExpression(JsSequenceExpression(sequence)) => {
+                        let has_comment = f.context().comments().has_comments(sequence.syntax());
+                        if has_comment {
+                            return write!(
+                                f,
+                                [group(&format_args![
+                                    format_signature,
+                                    group(&format_args![indent(&format_args![
+                                        hard_line_break(),
+                                        text("("),
+                                        soft_block_indent(&format_body),
+                                        text(")")
+                                    ]),])
+                                ])]
+                            );
+                        }
                         return write!(
                             f,
                             [group(&format_args![
@@ -473,6 +488,12 @@ impl Format<JsFormatContext> for ArrowChain {
             )
         });
 
+        let has_comment = matches!(
+          &tail_body,
+          AnyJsFunctionBody::AnyJsExpression(AnyJsExpression::JsSequenceExpression(sequence))
+          if f.context().comments().has_comments(sequence.syntax())
+        );
+
         let format_tail_body_inner = format_with(|f| {
             let format_tail_body = FormatMaybeCachedFunctionBody {
                 body: &tail_body,
@@ -485,14 +506,26 @@ impl Format<JsFormatContext> for ArrowChain {
                 tail_body,
                 AnyJsFunctionBody::AnyJsExpression(AnyJsExpression::JsSequenceExpression(_))
             ) {
-                write!(
-                    f,
-                    [group(&format_args![
-                        text("("),
-                        soft_block_indent(&format_tail_body),
-                        text(")")
-                    ])]
-                )?;
+                if has_comment {
+                    write!(
+                        f,
+                        [group(&format_args![indent(&format_args![
+                            hard_line_break(),
+                            text("("),
+                            soft_block_indent(&format_tail_body),
+                            text(")")
+                        ]),])]
+                    )?;
+                } else {
+                    write!(
+                        f,
+                        [group(&format_args![
+                            text("("),
+                            soft_block_indent(&format_tail_body),
+                            text(")")
+                        ])]
+                    )?;
+                }
             } else {
                 write!(f, [format_tail_body])?;
             }