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mdx-sanitizer

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Sanitize MDX content for Docusaurus builds. Fixes unescaped angle brackets (<, >, &lt;=, &gt;=), Liquid/Nunjucks template syntax ({{ }}), TypeScript generics (Promise&lt;T&gt;), and inline code backtick edge cases. Use when pre-commit hooks fail on bracket or Liquid validation, or when MDX/JSX build errors reference unexpected tokens. NOT for general markdown linting or prose editing.

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Source SKILL.md: https://github.com/curiositech/some_claude_skills/blob/HEAD/.claude/skills/mdx-sanitizer/SKILL.md

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MDX Sanitizer

Comprehensive MDX content sanitizer that prevents JSX parsing errors caused by angle brackets, generics, and other conflicting patterns.

The Problem

MDX 2.x treats unescaped < and { as JSX syntax. This causes build failures when content contains:

  • TypeScript generics: Promise&lt;T&gt;, Array&lt;string&gt;, Map&lt;K, V&gt;
  • Comparisons: &lt;100ms, &lt;=, &gt;=
  • Arrows: --&gt;, &lt;--, -&gt;
  • Invalid tags: &lt;link&gt; in prose, &lt;tag&gt; placeholders
  • Empty brackets: &lt;&gt;

Solution Architecture

This skill implements a three-layer defense:

1. Sync-Time Sanitization (Proactive)

Content is sanitized when syncing from .claude/skills/ to website/docs/:

  • syncSkillDocs.ts - Main skill files
  • syncSkillSubpages.ts - Reference files
  • doc-generator.ts - Generated docs

2. Pre-Commit Validation (Reactive)

The git pre-commit hook validates files before commit using validate-brackets.js.

3. Build-Time Validation (Final Check)

npm run validate:all runs as part of prebuild to catch any issues.

Usage

Check for Issues (Dry Run)

cd website
npm run sanitize:mdx
# or with verbose output
npm run sanitize:mdx -- --verbose

Fix All Issues

cd website
npm run sanitize:mdx -- --fix
# or shorthand
npm run fix:mdx

Programmatic API

import { sanitizeForMdx, validateMdxSafety, isMdxSafe } from './lib/mdx-sanitizer';

// Sanitize content
const result = sanitizeForMdx(content, { useHtmlEntities: true });
if (result.modified) {
  console.log(`Fixed ${result.issues.length} issues`);
  fs.writeFileSync(path, result.content);
}

// Validate without modifying
const issues = validateMdxSafety(content, 'path/to/file.md');

// Quick check
if (!isMdxSafe(content)) {
  // Handle issues
}

Escaping Strategies

The sanitizer uses HTML entities for maximum compatibility:

PatternOriginalEscaped
Less-than<&lt;
Greater-than>&gt;
Generics&lt;T&gt;&amp;lt;T&amp;gt;
Comparison&lt;=&amp;lt;=

Content inside code blocks (``` or `) is automatically protected and never escaped.

Files Modified

  • website/scripts/lib/mdx-sanitizer.ts - Core sanitizer module
  • website/scripts/sanitize-mdx.ts - CLI wrapper
  • website/scripts/syncSkillDocs.ts - Integration
  • website/scripts/syncSkillSubpages.ts - Integration
  • website/scripts/lib/doc-generator.ts - Integration
  • website/package.json - npm scripts

Patterns Detected

  1. Less-than before digit: &lt;100, &lt;0.5ms
  2. Comparison operators: &lt;=, &gt;=
  3. Empty brackets: &lt;&gt;
  4. Arrows: &lt;--, --&gt;
  5. Generic types: Promise&lt;T&gt;, Array&lt;string&gt;
  6. Space after less-than: &lt; value
  7. Invalid pseudo-tags: &lt;link&gt;, &lt;tag&gt; (not valid HTML)

Troubleshooting

Build Still Fails After Running Sanitizer

  1. Clear Docusaurus cache: npm run clear
  2. Re-run sanitizer: npm run sanitize:mdx -- --fix
  3. Rebuild: npm run build

False Positives

If valid JSX components are being escaped:

  • Ensure they use PascalCase (e.g., &lt;MyComponent&gt;)
  • Check they're valid HTML5 elements

Manual Escaping

For edge cases, manually escape in source:

  • Use backticks for inline code: `&lt;T&gt;`
  • Use fenced code blocks for multi-line
  • Use HTML entities: &lt; and &gt;

Sources