From 0423e0ea6735b8d2dc14f43d3fcb304861c130d6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Tiago?= <joao.leal.tintas@tecnico.ulisboa.pt>
Date: Thu, 28 Mar 2024 18:41:55 +0000
Subject: [PATCH] Fix #27605: inline math blocks can't be preceeded/followed by
 alphanumerical characters
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Inline math blocks couldn't be preceeded or succeeded by alphanumerical characters due to changes introduced in PR #21171. Removed the condition that caused this (precedingCharacter) and added a new if statement that checks if a specific '$' was escaped using '\'.
Signed-off-by: João Tiago <joao.leal.tintas@tecnico.ulisboa.pt>
---
 modules/markup/markdown/markdown_test.go      |  4 ++--
 modules/markup/markdown/math/inline_parser.go | 11 +++--------
 2 files changed, 5 insertions(+), 10 deletions(-)

diff --git a/modules/markup/markdown/markdown_test.go b/modules/markup/markdown/markdown_test.go
index ebac3fbe9e8e0..cddfb0c85166d 100644
--- a/modules/markup/markdown/markdown_test.go
+++ b/modules/markup/markdown/markdown_test.go
@@ -509,7 +509,7 @@ func TestMathBlock(t *testing.T) {
 		},
 		{
 			`$a a$b b$`,
-			`<p><code class="language-math is-loading">a a$b b</code></p>` + nl,
+			`<p><code class="language-math is-loading">a a</code>b b$</p>` + nl,
 		},
 		{
 			`a a$b b`,
@@ -517,7 +517,7 @@ func TestMathBlock(t *testing.T) {
 		},
 		{
 			`a$b $a a$b b$`,
-			`<p>a$b <code class="language-math is-loading">a a$b b</code></p>` + nl,
+			`<p>a<code class="language-math is-loading">b </code>a a<code class="language-math is-loading">b b</code></p>` + nl,
 		},
 		{
 			"$$a$$",
diff --git a/modules/markup/markdown/math/inline_parser.go b/modules/markup/markdown/math/inline_parser.go
index 0ac25c2b2ac86..ec49b4b24f7e0 100644
--- a/modules/markup/markdown/math/inline_parser.go
+++ b/modules/markup/markdown/math/inline_parser.go
@@ -55,12 +55,6 @@ func (parser *inlineParser) Parse(parent ast.Node, block text.Reader, pc parser.
 		return nil
 	}
 
-	precedingCharacter := block.PrecendingCharacter()
-	if precedingCharacter < 256 && isAlphanumeric(byte(precedingCharacter)) {
-		// need to exclude things like `a$` from being considered a start
-		return nil
-	}
-
 	// move the opener marker point at the start of the text
 	opener := len(parser.start)
 
@@ -75,14 +69,15 @@ func (parser *inlineParser) Parse(parent ast.Node, block text.Reader, pc parser.
 		ender += pos
 
 		// Now we want to check the character at the end of our parser section
-		// that is ender + len(parser.end)
+		// that is ender + len(parser.end) and check if char before ender is '\'
 		pos = ender + len(parser.end)
 		if len(line) <= pos {
 			break
 		}
-		if !isAlphanumeric(line[pos]) {
+		if  line[ender-1] != '\\' {
 			break
 		}
+
 		// move the pointer onwards
 		ender += len(parser.end)
 	}