From 429b65d60bb64973f1e5867cc58f1fe07bada952 Mon Sep 17 00:00:00 2001
From: hippotastic <6137925+hippotastic@users.noreply.github.com>
Date: Mon, 30 May 2022 18:18:33 +0200
Subject: [PATCH] Fix `*/` breaking HTML comments in Markdown (#3477)

---
 .changeset/polite-eels-visit.md                 |  5 +++++
 .../astro/src/vite-plugin-markdown/index.ts     |  5 +++--
 packages/astro/test/astro-markdown.test.js      |  7 +++++++
 .../astro-markdown/src/pages/comment-with-js.md | 17 +++++++++++++++++
 4 files changed, 32 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/polite-eels-visit.md
 create mode 100644 packages/astro/test/fixtures/astro-markdown/src/pages/comment-with-js.md

diff --git a/.changeset/polite-eels-visit.md b/.changeset/polite-eels-visit.md
new file mode 100644
index 000000000..00e573ac2
--- /dev/null
+++ b/.changeset/polite-eels-visit.md
@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Prevent `*/` from breaking HTML comments in Markdown
diff --git a/packages/astro/src/vite-plugin-markdown/index.ts b/packages/astro/src/vite-plugin-markdown/index.ts
index 997648a6b..38b36d27a 100644
--- a/packages/astro/src/vite-plugin-markdown/index.ts
+++ b/packages/astro/src/vite-plugin-markdown/index.ts
@@ -129,10 +129,11 @@ export default function markdown({ config }: AstroPluginOptions): Plugin {
 				// Extract special frontmatter keys
 				let { data: frontmatter, content: markdownContent } = matter(source);
 
-				// Turn HTML comments into JS comments
+				// Turn HTML comments into JS comments while preventing nested `*/` sequences
+				// from ending the JS comment by injecting a zero-width space
 				markdownContent = markdownContent.replace(
 					/<\s*!--([^-->]*)(.*?)-->/gs,
-					(whole) => `{/*${whole}*/}`
+					(whole) => `{/*${whole.replace(/\*\//g, '*\u200b/')}*/}`
 				);
 
 				let renderResult = await renderMarkdown(markdownContent, {
diff --git a/packages/astro/test/astro-markdown.test.js b/packages/astro/test/astro-markdown.test.js
index ecd6074ec..181ca56e9 100644
--- a/packages/astro/test/astro-markdown.test.js
+++ b/packages/astro/test/astro-markdown.test.js
@@ -72,6 +72,13 @@ describe('Astro Markdown', () => {
 		expect($('h1').text()).to.equal('It works!');
 	});
 
+	it('Prevents `*/` sequences from breaking HTML comments (#3476)', async () => {
+		const html = await fixture.readFile('/comment-with-js/index.html');
+		const $ = cheerio.load(html);
+
+		expect($('h1').text()).to.equal('It still works!');
+	});
+
 	// https://github.com/withastro/astro/issues/3254
 	it('Can handle scripts in markdown pages', async () => {
 		const html = await fixture.readFile('/script/index.html');
diff --git a/packages/astro/test/fixtures/astro-markdown/src/pages/comment-with-js.md b/packages/astro/test/fixtures/astro-markdown/src/pages/comment-with-js.md
new file mode 100644
index 000000000..387b8380e
--- /dev/null
+++ b/packages/astro/test/fixtures/astro-markdown/src/pages/comment-with-js.md
@@ -0,0 +1,17 @@
+<!--
+HTML comments with */ inside!
+-->
+
+<!--
+```js
+/**
+ * It even works inside nested fenced code blocks!
+ */
+function test() {
+	/* Yay */
+	return 'Nice!';
+}
+```
+-->
+
+# It still works!