From 2d3b5eb299b065d91e4ec64354c6a4dd9b96d3cc Mon Sep 17 00:00:00 2001
From: Boshen <boshenc@gmail.com>
Date: Fri, 17 Nov 2023 19:38:25 +0800
Subject: [PATCH] feat(prettier): add comments before expressions (#1375)

---
 crates/oxc_prettier/src/comment.rs    | 12 ++++++++----
 crates/oxc_prettier/src/format/mod.rs |  3 +++
 crates/oxc_prettier/src/lib.rs        |  9 +++------
 3 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/crates/oxc_prettier/src/comment.rs b/crates/oxc_prettier/src/comment.rs
index a5a14ea85..ab42411da 100644
--- a/crates/oxc_prettier/src/comment.rs
+++ b/crates/oxc_prettier/src/comment.rs
@@ -35,12 +35,16 @@ impl<'a> Prettier<'a> {
         false
     }
 
+    #[must_use]
     pub(crate) fn print_leading_comments(&mut self, range: Span) -> Option<Doc<'a>> {
-        let mut parts = vec![];
+        let mut parts = self.vec();
         while let Some((start, end, kind)) = self.trivias.peek().copied() {
             // Comment before the span
             if end <= range.start {
                 parts.push(self.print_comment(start, end, kind));
+                if kind.is_multi_line() {
+                    parts.push(hardline!());
+                }
                 self.trivias.next();
             } else {
                 break;
@@ -49,11 +53,10 @@ impl<'a> Prettier<'a> {
         if parts.is_empty() {
             return None;
         }
-        let mut comments = self.join(Separator::Hardline, parts);
-        comments.push(hardline!());
-        Some(Doc::Array(comments))
+        Some(Doc::Array(parts))
     }
 
+    #[must_use]
     pub(crate) fn print_dangling_comments(&mut self, range: Span) -> Option<Doc<'a>> {
         let mut parts = vec![];
         while let Some((start, end, kind)) = self.trivias.peek().copied() {
@@ -68,6 +71,7 @@ impl<'a> Prettier<'a> {
         (!parts.is_empty()).then(|| Doc::Array(self.join(Separator::Hardline, parts)))
     }
 
+    #[must_use]
     fn print_comment(&self, start: u32, end: u32, kind: CommentKind) -> Doc<'a> {
         let end_offset = if kind.is_multi_line() { 2 } else { 0 };
         let comment = Span::new(start - 2, end + end_offset).source_text(self.source_text);
diff --git a/crates/oxc_prettier/src/format/mod.rs b/crates/oxc_prettier/src/format/mod.rs
index 4fe675c23..9b80ecbb1 100644
--- a/crates/oxc_prettier/src/format/mod.rs
+++ b/crates/oxc_prettier/src/format/mod.rs
@@ -91,6 +91,9 @@ impl<'a> Format<'a> for Statement<'a> {
 impl<'a> Format<'a> for ExpressionStatement<'a> {
     fn format(&self, p: &mut Prettier<'a>) -> Doc<'a> {
         let mut parts = p.vec();
+        if let Some(doc) = p.print_leading_comments(self.span) {
+            parts.push(doc);
+        }
         parts.push(self.expression.format(p));
         if p.options.semi {
             parts.push(ss!(";"));
diff --git a/crates/oxc_prettier/src/lib.rs b/crates/oxc_prettier/src/lib.rs
index 8651ec690..57c0d1e2e 100644
--- a/crates/oxc_prettier/src/lib.rs
+++ b/crates/oxc_prettier/src/lib.rs
@@ -10,10 +10,7 @@ mod options;
 mod printer;
 mod util;
 
-use std::{
-    iter::{Peekable, Rev},
-    vec,
-};
+use std::{iter::Peekable, vec};
 
 use doc::Doc;
 use oxc_allocator::Allocator;
@@ -31,7 +28,7 @@ pub struct Prettier<'a> {
     options: PrettierOptions,
 
     /// A stack of comments that will be carefully placed in the right places.
-    trivias: Peekable<Rev<vec::IntoIter<(u32, u32, CommentKind)>>>,
+    trivias: Peekable<vec::IntoIter<(u32, u32, CommentKind)>>,
 }
 
 impl<'a> Prettier<'a> {
@@ -41,7 +38,7 @@ impl<'a> Prettier<'a> {
         trivias: Trivias,
         options: PrettierOptions,
     ) -> Self {
-        let trivias = trivias.into_iter().rev().peekable();
+        let trivias = trivias.into_iter().peekable();
         Self { allocator, source_text, options, trivias }
     }