From 218c34b11da536a2f607a59d5b5de586bc9a51ab Mon Sep 17 00:00:00 2001
From: yuxi-liu-wired <33951560+yuxi-liu-wired@users.noreply.github.com>
Date: Sun, 4 Oct 2026 21:43:35 +0000
Subject: [PATCH] Skip the leading spaces of a lazy continuation line

A paragraph line's leading spaces and tabs are not part of the
paragraph's raw content (spec 4.8), and cmark skips them for a normal
continuation line. A lazy continuation line was added from the current
offset instead, so its leading space stayed in the content. That shows
in a code span, where the line ending becomes a space:

    > `a
     b`

rendered `<code>a  b</code>` (two spaces); commonmark.js gives
`<code>a b</code>`. The same in a list item (`- \`c\n d\``).

Advance past the leading whitespace before adding the lazy line, as the
non-lazy paragraph path does.
---
 src/blocks.c        |  3 +++
 test/regression.txt | 18 ++++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/src/blocks.c b/src/blocks.c
index 8ff339ee4..b0db722cd 100644
--- a/src/blocks.c
+++ b/src/blocks.c
@@ -1196,6 +1196,9 @@ static void add_text_to_container(cmark_parser *parser, cmark_node *container,
   if (parser->current != last_matched_container &&
       container == last_matched_container && !parser->blank &&
       S_type(parser->current) == CMARK_NODE_PARAGRAPH) {
+    // Like any paragraph line, skip the leading spaces and tabs.
+    S_advance_offset(parser, input, parser->first_nonspace - parser->offset,
+                     false);
     add_line(input, parser);
   } else { // not a lazy continuation
     // Finalize any blocks that were not matched and set cur to container:
diff --git a/test/regression.txt b/test/regression.txt
index 1426617ab..454be0cb8 100644
--- a/test/regression.txt
+++ b/test/regression.txt
@@ -108,6 +108,24 @@ City:
 </span></p>
 ````````````````````````````````
 
+The leading spaces of a lazy continuation line are not part of the
+paragraph content, as for any other paragraph line.
+
+```````````````````````````````` example
+> `a
+ b`
+
+- `c
+ d`
+.
+<blockquote>
+<p><code>a b</code></p>
+</blockquote>
+<ul>
+<li><code>c d</code></li>
+</ul>
+````````````````````````````````
+
 Issue #530 - link parsing corner cases
 
 ```````````````````````````````` example