From b2e8490f6adb0b5e73f66c61b907cb0316a2cb49 Mon Sep 17 00:00:00 2001
From: "James D. Forrester" <jforrester@wikimedia.org>
Date: Mon, 27 Jul 2026 17:18:25 +0100
Subject: [PATCH] fix: preserve source.input.file when retokenizing inline
 comments

The replacement Input built for the remainder of the file was constructed
without options, so `from` was dropped and every node after an inline comment
reported `source.input.file === undefined`. lib/index.js already repairs the
start/end offsets the sub-tokenizer corrupts, but not `source.input`, so the
missing path reached the returned AST.

Input does not retain its opts, so `from` is reconstructed from
`this.input.file` rather than forwarded wholesale.
---
 lib/nodes/inline-comment.js  |  2 +-
 test/parser/comments.test.js | 29 +++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/lib/nodes/inline-comment.js b/lib/nodes/inline-comment.js
index b933949..6d4a461 100644
--- a/lib/nodes/inline-comment.js
+++ b/lib/nodes/inline-comment.js
@@ -45,7 +45,7 @@ module.exports = {
       // Replace tokenizer to retokenize the rest of the string
       // we need replace it after we added new token with inline comment because token position is calculated for old input (#145)
       if (remainingInput) {
-        this.input = new Input(remainingInput);
+        this.input = new Input(remainingInput, { from: this.input.file });
         this.tokenizer = tokenizer(this.input);
       }
 
diff --git a/test/parser/comments.test.js b/test/parser/comments.test.js
index 6f7fdc1..952c472 100644
--- a/test/parser/comments.test.js
+++ b/test/parser/comments.test.js
@@ -212,3 +212,32 @@ test('handles single quotes in comments (#163)', (t) => {
 
   t.is(nodeToString(root), less);
 });
+
+test('preserves source.input.file when retokenizing inline comments', (t) => {
+  const from = '/repro.less';
+  // The quote in the inline comment, plus a later quote, makes the tokenizer run
+  // the string past the newline, which sends `isInlineComment` down the path that
+  // builds a replacement Input for the remainder of the file.
+  const less = `a {\n  // it's\n  color: red;\n}\nb { content: 'x'; }\n`;
+
+  const root = parse(less, { from });
+
+  const nodes = [];
+  root.walk((node) => nodes.push(node));
+
+  // Nodes produced by the replacement tokenizer must keep the original path.
+  for (const node of nodes) {
+    t.is(node.source.input.file, from);
+  }
+
+  // The position fix-up in lib/index.js still applies.
+  t.deepEqual(nodes.map((node) => [node.type, node.source.start.line]), [
+    ['rule', 1],
+    ['comment', 2],
+    ['decl', 3],
+    ['rule', 5],
+    ['decl', 5]
+  ]);
+
+  t.is(nodeToString(root), less);
+});