Markdown Meta Action

Fact Sheet
Author	mheap
Contributors	1
Stars	0
Repo	https://github.com/mheap/markdown-meta-action
Marketplace	https://github.com/marketplace/actions/markdown-meta

What does it do?

Content containing some YAML frontmatter is very common nowadays (in fact, you're reading a post that uses it right now).

markdown-meta allows you to read that metadata and makes it available as an output in your GitHub Actions workflow.

The frontmatter for this file is as follows:

title: Markdown Meta Action
description: Read the frontmatter from your markdown files and use the values in your workflows
slug: markdown-meta-action
date: "2021-05-07T19:01:58+01:00"
category: "Action Spotlight"
tags:
  - github-actions

Given that file we can run the following workflow that outputs the post title:

name: Get Post Meta
on: push
jobs:
  post-meta:
    name: Post Meta
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v2
      - name: Markdown Meta
        uses: mheap/markdown-meta-action@v1
        id: meta
        with:
          file: ./_posts/markdown-meta-action.md
      - name: Output the post title
        run: echo "${{ steps.meta.outputs.title }}"

We use the id parameter to name the markdown-meta step meta and then access the data returned by it using steps.meta.outputs. Each key in the frontmatter is available:

• steps.meta.outputs.title
• steps.meta.outputs.description
• steps.meta.outputs.slug
• steps.meta.outputs.date
• steps.meta.outputs.category
• steps.meta.outputs.tags

How does it work?

This is a really tiny action, just 7 lines long:

• It fetches the filename to read from the file input and reads the content into a string
• Next, it uses the gray-matter library to extract the frontmatter
• Then for each value in the frontmatter, it sets an output. The key name is run through slugify to remove special characters and whitespace
  • a key with spaces becomes a-key-with-spaces
  • t!tle becomes ttle
  • 🚀 lift-off becomes lift-off

As it uses core.setOutput() any complex data types such as objects or arrays are JSON encoded before being output. This means that in the above example, tags will be ["github-actions"].

Common use cases

The best use case that I can think of for this action is automated blog post updates:

name: Get Post Meta
on: push
jobs:
  post-meta:
    name: Post Meta
    runs-on: ubuntu-latest
    steps:
      - name: Checkout
        uses: actions/checkout@v2
      - name: Get latest post
        run: |
          cd _posts
          echo "::set-output name=post_name::$(ls -rt | tail -n 1)"
        id: latest_post
      - name: Markdown Meta
        uses: mheap/markdown-meta-action@v1
        id: meta
        with:
          file: ./_posts/${{ steps.latest_post.outputs.post_name }}
      - uses: ethomson/send-tweet-action@v1
        with:
          status: "I just published! ${{ steps.meta.outputs.title }} https://michaelheap.com/${{ steps.meta.outputs.slug }}"
          consumer-key: ${{ secrets.TWITTER_CONSUMER_API_KEY }}
          consumer-secret: ${{ secrets.TWITTER_CONSUMER_API_SECRET }}
          access-token: ${{ secrets.TWITTER_ACCESS_TOKEN }}
          access-token-secret: ${{ secrets.TWITTER_ACCESS_TOKEN_SECRET }}