From d74013c64200125e2f61d49e9acf4517bcef9328 Mon Sep 17 00:00:00 2001
From: Sidharth Vinod <sidharthv96@gmail.com>
Date: Thu, 14 Aug 2025 13:05:44 +0530
Subject: [PATCH] fix: Remove data loss when unsupported markdown is
 encountered

---
 .../mermaid/src/rendering-util/handle-markdown-text.spec.ts | 6 +++++-
 packages/mermaid/src/rendering-util/handle-markdown-text.ts | 4 +++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/packages/mermaid/src/rendering-util/handle-markdown-text.spec.ts b/packages/mermaid/src/rendering-util/handle-markdown-text.spec.ts
index 3ab4167a2..2000d58b8 100644
--- a/packages/mermaid/src/rendering-util/handle-markdown-text.spec.ts
+++ b/packages/mermaid/src/rendering-util/handle-markdown-text.spec.ts
@@ -285,7 +285,11 @@ test('markdownToHTML - Unsupported formatting', () => {
   - l1
   - l2
   - l3`)
-  ).toMatchInlineSnapshot('"<p>Hello</p>Unsupported markdown: list"');
+  ).toMatchInlineSnapshot(`
+    "<p>Hello</p>  - l1
+      - l2
+      - l3"
+  `);
 });
 
 test('markdownToHTML - no auto wrapping', () => {
diff --git a/packages/mermaid/src/rendering-util/handle-markdown-text.ts b/packages/mermaid/src/rendering-util/handle-markdown-text.ts
index f898875cf..82e94c2c2 100644
--- a/packages/mermaid/src/rendering-util/handle-markdown-text.ts
+++ b/packages/mermaid/src/rendering-util/handle-markdown-text.ts
@@ -3,6 +3,7 @@ import { marked } from 'marked';
 import { dedent } from 'ts-dedent';
 import type { MarkdownLine, MarkdownWordType } from './types.js';
 import type { MermaidConfig } from '../config.type.js';
+import { log } from '../logger.js';
 
 /**
  * @param markdown - markdown to process
@@ -89,7 +90,8 @@ export function markdownToHTML(markdown: string, { markdownAutoWrap }: MermaidCo
     } else if (node.type === 'escape') {
       return node.text;
     }
-    return `Unsupported markdown: ${node.type}`;
+    log.warn(`Unsupported markdown: ${node.type}`);
+    return node.raw;
   }
 
   return nodes.map(output).join('');