Source blocks (#+BEGIN_SRC / #+END_SRC) were not rendering correctly
in preview cards. The content was being displayed as raw Org Mode syntax
instead of formatted code blocks.
This fix:
- Detects source blocks using regex pattern matching
- Extracts code content and language identifier
- HTML-escapes code content to prevent XSS
- Replaces blocks with placeholders before other formatting
- Restores blocks as styled <pre><code> elements after line break conversion
Fixes issue where comments and code in source blocks were invisible
in share preview links.
