mdformat-gfm-alerts

An mdformat plugin for GFM Alerts. For the JS markdown-it equivalent, see antfu/markdown-it-github-alerts

Scope

By default, this package targets the alert syntax GitHub itself renders: [!NOTE], [!TIP], [!IMPORTANT], [!WARNING], and [!CAUTION] alone on their own line, per GitHub's alerts spec. Custom titles ([!TIP] Title) and fold indicators aren't part of that spec, so this package folds trailing text on the marker line into the alert body instead of treating it as a title, matching how GitHub itself would render it.

Obsidian's callout syntax (open-ended types, fold indicators, and custom titles) is where this convention originates. Hugo's alert syntax mirrors just the custom-title/fold grammar, restricted to GFM's five types. Pass --custom-title (or the custom_title option, see Configuration) to preserve an inline title on the canonical [!TYPE] line instead of folding it into the body. This package still won't support fold indicators or Obsidian's open-ended callout types. For that:

• mdformat-hugo bundles this package alongside Hugo-specific shortcode and markdown-attribute formatting
• mdformat-obsidian fully supports GFM-style alerts plus custom titles, folding, and Obsidian's open-ended callout types

Configuration

--custom-title (CLI), custom_title = true under [plugin.gfm_alerts] (.mdformat.toml), or options={"custom_title": True} (API) preserves an inline custom title on the canonical [!TYPE] line instead of folding it into the body:

<!-- Strict GFM (default): -->
> [!TIP]
> Custom title
> Body.

<!-- With --custom-title: -->
> [!TIP] Custom title
> Body.

mdformat Usage

Add this package wherever you use mdformat; it auto-recognizes the plugin, no configuration needed. See more on mdformat plugins

pre-commit / prek

repos:
  - repo: https://github.com/executablebooks/mdformat
    rev: 1.0.0
    hooks:
      - id: mdformat
        additional_dependencies:
          - mdformat-gfm-alerts

uvx

uvx --with=mdformat-gfm-alerts mdformat

Or with pipx:

pipx install mdformat
pipx inject mdformat mdformat-gfm-alerts

HTML Rendering

To generate HTML output, import gfm_alerts_plugin from mdit_plugins. For more on MarkdownIt, see the docs: https://markdown-it-py.readthedocs.io/en/latest/using.html#the-parser

from markdown_it import MarkdownIt

from mdformat_gfm_alerts.mdit_plugins import gfm_alerts_plugin

md = MarkdownIt()
md.use(gfm_alerts_plugin)  # pass custom_title=True to preserve inline custom titles

text = """
> [!WARNING]
> This is the warning text
"""
md.render(text)
# <div class="markdown-alert markdown-alert-warning">
# <p class="markdown-alert-title">Warning</p>
# <p>This is the warning text</p>
# </div>

Contributing

See CONTRIBUTING.md