Markdown Formatter

Markdown Formatter

Purpose

Provide comprehensive markdown formatting rules and automated fixes to ensure consistent, clean, and standards-compliant markdown documentation across a project. This skill covers 12 core linting rules, context-aware fixes, configuration options, and integration patterns for CI/CD pipelines and editor workflows.

When to Use

• When writing or editing markdown documentation
• When linting markdown files before commit
• When enforcing consistent formatting across a repository
• When integrating markdown quality checks into CI/CD
• When onboarding a team to documentation standards

Formatting Rules

Rule 1: MD007 -- Unordered List Indentation

Use consistent 2-space indentation for nested unordered lists.

Incorrect:

- Item 1
    - Nested (4 spaces)
      - Deep nested (6 spaces)

Correct:

- Item 1
  - Nested (2 spaces)
    - Deep nested (4 spaces)

Rule 2: MD012 -- Multiple Consecutive Blank Lines

Never use more than one consecutive blank line. A single blank line provides readability; additional blank lines add no value.

Incorrect:

## Section 1


## Section 2

Correct:

## Section 1

## Section 2

Rule 3: MD022 -- Headings Surrounded by Blank Lines

Always add a blank line before and after headings.

Incorrect:

Some paragraph text.
## Heading
More text here.

Correct:

Some paragraph text.

## Heading

More text here.

Rule 4: MD024 -- Duplicate Heading Content

Avoid duplicate heading text within the same document. Add context to differentiate headings with the same name.

Incorrect:

## Setup
... (for backend)

## Setup
... (for frontend)

Correct:

## Backend Setup
...

## Frontend Setup
...

Rule 5: MD026 -- Trailing Punctuation in Headings

Do not end headings with punctuation characters (period, exclamation, question mark, colon).

Incorrect:

## Getting Started:

## What is this?

Correct:

## Getting Started

## About This Project

Rule 6: MD029 -- Ordered List Item Prefix

Use sequential numbering for ordered lists (1, 2, 3) or all-ones (1, 1, 1) consistently.

Incorrect:

1. First
1. Second
3. Third

Correct:

1. First
2. Second
3. Third

Rule 7: MD031 -- Fenced Code Blocks Surrounded by Blank Lines

Always add a blank line before and after fenced code blocks.

Incorrect:

Some text.
```javascript
const x = 1;
```
More text.

Correct:

Some text.

```javascript
const x = 1;
```

More text.

Rule 8: MD032 -- Lists Surrounded by Blank Lines

Always add a blank line before and after list blocks.

Incorrect:

Some paragraph.
- Item 1
- Item 2
Another paragraph.

Correct:

Some paragraph.

- Item 1
- Item 2

Another paragraph.

Rule 9: MD036 -- Emphasis Used Instead of Heading

Do not use bold or italic text as a substitute for proper headings.

Incorrect:

**This is a section title**

Content goes here.

Correct:

## This is a section title

Content goes here.

Rule 10: MD040 -- Fenced Code Blocks Language Specification

Always specify a language identifier on fenced code blocks for proper syntax highlighting. Use text for plain text blocks.

Incorrect:

```
const x = 1;
```

Correct:

```javascript
const x = 1;
```

Rule 11: MD051 -- Valid Link Fragments

Internal anchor links must point to existing headings in the document.

Incorrect:

See the [setup section](#set-up)  <!-- heading is "## Setup" -->

Correct:

See the [setup section](#setup)

Rule 12: MD058 -- Tables Surrounded by Blank Lines

Always add a blank line before and after tables.

Incorrect:

Some text.
| Column | Column |
|--------|--------|
| Value  | Value  |
More text.

Correct:

Some text.

| Column | Column |
|--------|--------|
| Value  | Value  |

More text.

Configuration

Rule Selection

rules:
  enabled:
    - MD007  # List indentation
    - MD012  # Multiple blank lines
    - MD022  # Heading blank lines
    - MD024  # Duplicate headings
    - MD026  # Heading punctuation
    - MD029  # Ordered list prefix
    - MD031  # Code block blank lines
    - MD032  # List blank lines
    - MD036  # Emphasis as heading
    - MD040  # Code block language
    - MD051  # Link fragments
    - MD058  # Table blank lines

Formatting Preferences

formatting:
  indentation: 2           # Spaces for list indentation
  line_length: 100         # Max line length (soft wrap)
  blank_lines_max: 1       # Max consecutive blank lines
  code_language_default: 'text'  # Default code block language
  heading_style: 'atx'    # Use # style headings
  ordered_list_style: 'sequential'  # 1, 2, 3 (not 1, 1, 1)

File Patterns

files:
  include: ['**/*.md', '**/*.markdown']
  exclude: ['node_modules/**', 'dist/**', 'build/**', '.git/**']
  respect_gitignore: true

Process

Step 1: Parse

Read and tokenize markdown content into an AST (Abstract Syntax Tree).

Step 2: Analyze

Detect rule violations using AST analysis. Identify:

• Structural issues (blank lines, indentation)
• Semantic issues (duplicate headings, emphasis-as-heading)
• Content issues (missing language specs, broken links)

Step 3: Fix

Apply corrections while preserving content integrity:

• Add or remove blank lines
• Normalize indentation
• Add language identifiers to code blocks
• Resolve duplicate headings with context

Step 4: Validate

After fixes, re-analyze to confirm:

• No new violations introduced
• Content semantics preserved
• Links still resolve correctly

Context-Aware Fixes

Code Block Language Detection

When adding language identifiers to unlabeled code blocks:

1. Analyze surrounding text for technology references
2. Examine code syntax patterns (imports, keywords, brackets)
3. Check for file extension hints in nearby text
4. Default to text for ambiguous blocks

Heading Deduplication

When resolving duplicate headings:

1. Analyze the section context
2. Add descriptive prefixes or suffixes
3. Preserve semantic meaning
4. Flag complex cases for manual review

List Indentation Normalization

When fixing list indentation:

1. Detect existing indentation pattern
2. Normalize to 2-space standard
3. Preserve nested relationships
4. Handle mixed ordered/unordered lists correctly

Integration

Pre-Commit Hook

# .husky/pre-commit or similar
npx markdownlint-cli2 "**/*.md"

CI/CD Pipeline

# GitHub Actions example
- name: Lint Markdown
  run: npx markdownlint-cli2 "**/*.md" "#node_modules"

Editor Integration

• VS Code: markdownlint extension
• Format on save with configured rules
• Inline error highlighting
• Quick fix suggestions

Best Practices

1. Run on clean git state -- easy rollback if fixes cause issues
2. Review changes before committing -- automated fixes may need adjustment
3. Configure rules per project -- not all rules suit every project
4. Use validation mode first -- check before fixing on new codebases
5. Integrate into CI -- catch violations before merge
6. Document exceptions -- if a rule is disabled, note why
7. Keep rules consistent -- same rules across all project documentation
8. Separate formatting commits -- do not mix content changes with formatting fixes
9. Use a linting tool -- markdownlint, remark-lint, or similar
10. Train contributors -- share formatting guidelines in CONTRIBUTING.md

Error Handling

• Continue processing on individual rule failures
• Provide detailed error reporting with file and line numbers
• Skip binary files automatically
• Handle large files without performance degradation
• Support Unicode and various text encodings

Reporting

After formatting, produce:

• Number of files processed
• Violations found per rule
• Fixes applied per rule
• Files requiring manual attention
• Before/after summary