From bcc3067087b60a2913938d0bca77a71dacc06ba2 Mon Sep 17 00:00:00 2001
From: Tony Brix <tony@brix.ninja>
Date: Fri, 15 Sep 2023 13:22:12 -0600
Subject: [PATCH] fix: fix unexpected setext heading (#2986)

---
 src/rules.ts                         |  2 +-
 test/specs/new/setext_blankline.html |  9 +++++++++
 test/specs/new/setext_blankline.md   | 11 +++++++++++
 3 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 test/specs/new/setext_blankline.html
 create mode 100644 test/specs/new/setext_blankline.md

diff --git a/src/rules.ts b/src/rules.ts
index 1c6fda259f..c49fb8328a 100644
--- a/src/rules.ts
+++ b/src/rules.ts
@@ -87,7 +87,7 @@ export const block: Record<BlockRuleNames, Rule> & Record<BlockSubRuleNames, Rul
     + ')',
   def: /^ {0,3}\[(label)\]: *(?:\n *)?([^<\s][^\s]*|<.*?>)(?:(?: +(?:\n *)?| *\n *)(title))? *(?:\n+|$)/,
   table: noopTest,
-  lheading: /^((?:(?!^bull ).|\n(?!\n|bull ))+?)\n {0,3}(=+|-+) *(?:\n+|$)/,
+  lheading: /^(?!bull )((?:.|\n(?!\s*?\n|bull ))+?)\n {0,3}(=+|-+) *(?:\n+|$)/,
   // regex template, placeholders will be replaced according to different paragraph
   // interruption rules of commonmark and the original markdown spec:
   _paragraph: /^([^\n]+(?:\n(?!hr|heading|lheading|blockquote|fences|list|html|table| +\n)[^\n]+)*)/,
diff --git a/test/specs/new/setext_blankline.html b/test/specs/new/setext_blankline.html
new file mode 100644
index 0000000000..1b3ebc2c87
--- /dev/null
+++ b/test/specs/new/setext_blankline.html
@@ -0,0 +1,9 @@
+<p>a</p>
+<p>b</p>
+<p>=</p>
+
+<p>a</p>
+<p>b</p>
+<ul>
+  <li></li>
+</ul>
diff --git a/test/specs/new/setext_blankline.md b/test/specs/new/setext_blankline.md
new file mode 100644
index 0000000000..7214ac6298
--- /dev/null
+++ b/test/specs/new/setext_blankline.md
@@ -0,0 +1,11 @@
+a
+ 
+b
+ 
+=
+
+a
+ 
+b
+ 
+-