From f05fe5754d01774a2f522311b6e4f44399f8d2cf Mon Sep 17 00:00:00 2001
From: Justin Charles <143245796+justin212407@users.noreply.github.com>
Date: Tue, 10 Mar 2026 17:01:38 +0530
Subject: [PATCH] Desktop: Fixes #14542: Fix Prevent unclosed frontmatter from
 breaking Markdown rendering (#14563)

Signed-off-by: justin212407 <charlesjustin2124@gmail.com>
---
 .../markdownFrontMatterExtension.test.ts      | 11 ++++
 .../markdownFrontMatterExtension.ts           | 56 +++++++++----------
 2 files changed, 38 insertions(+), 29 deletions(-)

diff --git a/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.test.ts b/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.test.ts
index 1a309a63d1..3bf58a212e 100644
--- a/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.test.ts
+++ b/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.test.ts
@@ -54,6 +54,17 @@ describe('MarkdownFrontMatterExtension', () => {
 		expect(frontMatterNodes.length).toBe(0);
 	});
 
+	it('should treat the entire document as frontmatter when closing delimiter is missing (issue #14542)', async () => {
+		const documentText = '---\nsome: frontmatter\n--\n\n# Hey';
+		const editor = await createEditorState(documentText, [frontMatterTagName]);
+		const frontMatterNodes = findNodesWithName(editor, frontMatterTagName);
+
+		// Frontmatter block must be recognised and span the entire document
+		expect(frontMatterNodes.length).toBe(1);
+		expect(frontMatterNodes[0].from).toBe(0);
+		expect(frontMatterNodes[0].to).toBe(documentText.length);
+	});
+
 	it('should handle empty FrontMatter block', async () => {
 		const documentText = '---\n---\n\n# Heading';
 		const editor = await createEditorState(documentText, [frontMatterTagName, 'ATXHeading1']);
diff --git a/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.ts b/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.ts
index d332e60718..4e29f4946d 100644
--- a/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.ts
+++ b/packages/editor/CodeMirror/extensions/markdownFrontMatterExtension.ts
@@ -66,14 +66,15 @@ const frontMatterConfig: MarkdownConfig = {
 				return false;
 			}
 
-			// Store the opening delimiter position
+			// If the document starts with --- always claim it as a frontmatter block,
+			// even when the closing delimiter is absent.
 			const openingMarkerStart = cx.lineStart;
 			const openingMarkerEnd = cx.lineStart + line.text.length;
+			const contentStart = openingMarkerEnd + 1;
 
-			const contentStart = openingMarkerEnd + 1; // Start after the opening --- and newline
 			let foundEnd = false;
 
-			// Consume lines until we find the closing ---
+			// Consume lines until we find the closing --- or reach end of document.
 			while (cx.nextLine()) {
 				if (frontMatterDelimiterRegex.test(line.text)) {
 					foundEnd = true;
@@ -81,37 +82,34 @@ const frontMatterConfig: MarkdownConfig = {
 				}
 			}
 
-			if (!foundEnd) {
-				// No closing delimiter found - not a valid FrontMatter block
-				return false;
-			}
+			// cx.lineStart now points to the closing --- (if found) or end of document (if not).
+			const contentEnd = cx.lineStart;
 
-			// The content is between the two --- delimiters
-			const contentEnd = cx.lineStart; // Start of the closing --- line
-
-			// Closing delimiter positions
-			const closingMarkerStart = cx.lineStart;
-			const closingMarkerEnd = cx.lineStart + line.text.length;
-
-			// Create marker elements for the --- delimiters
 			const openingMarkerElem = cx.elt(frontMatterMarkerTagName, openingMarkerStart, openingMarkerEnd);
-			const closingMarkerElem = cx.elt(frontMatterMarkerTagName, closingMarkerStart, closingMarkerEnd);
-
-			// Create the content element (the YAML content between delimiters)
 			const contentElem = cx.elt(frontMatterContentTagName, contentStart, contentEnd);
 
-			// Create the container element spanning from start of first --- to end of last ---
-			const containerElement = cx.elt(
-				frontMatterTagName,
-				0, // Start at document beginning
-				closingMarkerEnd, // End after closing ---
-				[openingMarkerElem, contentElem, closingMarkerElem],
-			);
+			if (foundEnd) {
+				const closingMarkerStart = cx.lineStart;
+				const closingMarkerEnd = cx.lineStart + line.text.length;
+				const closingMarkerElem = cx.elt(frontMatterMarkerTagName, closingMarkerStart, closingMarkerEnd);
 
-			cx.addElement(containerElement);
-
-			// Move past the closing delimiter
-			cx.nextLine();
+				const containerElement = cx.elt(
+					frontMatterTagName,
+					0,
+					closingMarkerEnd,
+					[openingMarkerElem, contentElem, closingMarkerElem],
+				);
+				cx.addElement(containerElement);
+				cx.nextLine();
+			} else {
+				const containerElement = cx.elt(
+					frontMatterTagName,
+					0,
+					contentEnd,
+					[openingMarkerElem, contentElem],
+				);
+				cx.addElement(containerElement);
+			}
 
 			return true;
 		},