From 1306649a6530dfa54294458ef720a64013072a05 Mon Sep 17 00:00:00 2001
From: yuin <yuin@inforno.net>
Date: Sat, 11 Sep 2021 11:51:43 +0900
Subject: [PATCH] Fix #245 - 6

---
 _test/extra.txt       | 7 +++++++
 parser/atx_heading.go | 3 +++
 2 files changed, 10 insertions(+)

diff --git a/_test/extra.txt b/_test/extra.txt
index 197a3f5..96715df 100644
--- a/_test/extra.txt
+++ b/_test/extra.txt
@@ -409,3 +409,10 @@ hello\x00world
 <p><code>x </code></p>
 <p><code> x</code></p>
 //= = = = = = = = = = = = = = = = = = = = = = = =//
+
+28: Single # is a heading level 1
+//- - - - - - - - -//
+#
+//- - - - - - - - -//
+<h1></h1>
+//= = = = = = = = = = = = = = = = = = = = = = = =//
diff --git a/parser/atx_heading.go b/parser/atx_heading.go
index 2526088..13a198b 100644
--- a/parser/atx_heading.go
+++ b/parser/atx_heading.go
@@ -91,6 +91,9 @@ func (b *atxHeadingParser) Open(parent ast.Node, reader text.Reader, pc Context)
 	if i == pos || level > 6 {
 		return nil, NoChildren
 	}
+	if i == len(line) { // alone '#' (without a new line character)
+		return ast.NewHeading(level), NoChildren
+	}
 	l := util.TrimLeftSpaceLength(line[i:])
 	if l == 0 {
 		return nil, NoChildren