From ed07d6537dc1d10169b8529dfe3d13e9609f0162 Mon Sep 17 00:00:00 2001
From: Yarchik <spoko.dev@gmail.com>
Date: Wed, 24 Jun 2026 02:25:10 +0100
Subject: [PATCH] fix: preserve blank line after inline block comment in
 stringify

A blank line after an inline block comment (/* ... */) that follows a
comma was silently dropped by stringify, while the identical case with a
line comment (// ...) round-tripped correctly.

The parse trees for both cases are identical (both carry the BlankLine
token), so the defect is in stringify. In join(), the one && two branch
did one + two.trim() + LF + gap, and two.trim() discarded the blank-line
count carried by two. The line-comment case survived only because
process_comments appends a trailing LF after a LineComment, which landed
the missing break in one by coincidence.

Emit the blank lines that two carries beyond those already supplied by
the trailing LF + gap and the trailing line breaks of one.
---
 src/stringify.js       | 36 ++++++++++++++++++++++++++++++++++--
 test/stringify.test.js | 30 ++++++++++++++++++++++++++++++
 2 files changed, 64 insertions(+), 2 deletions(-)

diff --git a/src/stringify.js b/src/stringify.js
index 75a3c7e..8c2680a 100644
--- a/src/stringify.js
+++ b/src/stringify.js
@@ -62,6 +62,26 @@ const count_trailing_line_breaks = str => {
   return count
 }
 
+const count_leading_line_breaks = str => {
+  let i = 0
+  let count = 0
+
+  while (i < str.length) {
+    while (i < str.length && is_inline_whitespace(str[i])) {
+      i ++
+    }
+
+    if (i === str.length || str[i] !== LF) {
+      return count
+    }
+
+    i ++
+    count ++
+  }
+
+  return count
+}
+
 // display_block `boolean` whether the
 //   WHOLE block of comments is always a block group
 const process_comments = (host, symbol_tag, deeper_gap, display_block) => {
@@ -138,8 +158,20 @@ const join = (one, two, gap) =>
       // Symbol.for('before') and Symbol.for('before:prop')
       // might both exist if user mannually add comments to the object
       // and make a mistake.
-      // SO, we are not to only trimRight but trim for both sides
-      ? one + two.trim() + LF + gap
+      // SO, we are not to only trimRight but trim for both sides.
+      // The trailing `LF + gap` plus the trailing line breaks of `one`
+      // already supply some line breaks, so only emit the blank lines that
+      // `two` carries beyond those, otherwise `two.trim()` would drop them.
+      ? one
+        + repeat_line_breaks(
+          Math.max(
+            count_leading_line_breaks(two)
+              - count_trailing_line_breaks(one) - 1,
+            0
+          ),
+          gap
+        )
+        + two.trim() + LF + gap
       : one.trimRight() + repeat_line_breaks(
         Math.max(1, count_trailing_line_breaks(one)),
         gap
diff --git a/test/stringify.test.js b/test/stringify.test.js
index 6d6c360..b7a9d8f 100644
--- a/test/stringify.test.js
+++ b/test/stringify.test.js
@@ -219,6 +219,36 @@ test('preserve blank lines after before comments', t => {
   t.is(output, content)
 })
 
+test('preserve blank line after inline block comment following a comma', t => {
+  const content = `{
+  "a": 1, /* x */
+
+  "b": 2
+}`
+
+  t.is(stringify(parse(content), null, 2), content)
+})
+
+test('preserve blank line after inline line comment following a comma', t => {
+  const content = `{
+  "a": 1, // x
+
+  "b": 2
+}`
+
+  t.is(stringify(parse(content), null, 2), content)
+})
+
+test('preserve blank line after inline block comment in arrays', t => {
+  const content = `[
+  1, /* x */
+
+  2
+]`
+
+  t.is(stringify(parse(content), null, 2), content)
+})
+
 test('render explicit BlankLine tokens between comments', t => {
   const comments = [
     {