astro/docs/markdown.md at ffb6380c3fde97e67c94a374d177b7fb4ca809c5

* wip: serverside render dynamic Markdown content

* docs: update Markdown.astro comments

* Use existing markdown infrastructure to render external MD

* Update Markdown docs

* Add a changeset

Co-authored-by: Matthew Phillips <matthew@skypack.dev>

2021-06-02 11:53:33 -04:00

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✍️ Markdown

Astro comes with out-of-the-box Markdown support powered by the expansive remark ecosystem.

Remark Plugins

This is the first draft of Markdown support! While we plan to support user-provided remark plugins soon, our hope is that you won't need remark plugins at all!

In addition to custom components inside the <Markdown> component, Astro comes with GitHub-flavored Markdown support, Footnotes syntax, Smartypants, and syntax highlighting via Prism pre-enabled. These features are likely to be configurable in the future.

Markdown Pages

Astro treats any .md files inside of the /src/pages directory as pages. These pages are processed as plain Markdown files and do not support components. If you're looking to embed rich components in your Markdown, take a look at the Markdown Component section.

`layout`

The only special Frontmatter key is layout, which defines the relative path to a .astro component which should wrap your Markdown content.

src/pages/index.md

---
layout: ../layouts/main.astro
---

# Hello world!

Layout files are normal .astro components. Any Frontmatter defined in your .md page will be exposed to the Layout component as the content prop. content also has an astro key which holds special metadata about your file, like the complete Markdown source and a headings object.

The rendered Markdown content is placed into the default <slot /> element.

src/layouts/main.astro

---
export let content;
---

<html>
  <head>
    <title>{content.title}</title>
  </head>

  <body>
    <slot/>
  </body>
</html>

Markdown Component

Similar to tools like MDX or MDsveX, Astro makes it straightforward to embed rich, interactive components inside of your Markdown content. The <Markdown> component is statically rendered, so it does not add any runtime overhead.

Astro exposes a special Markdown component for .astro files which enables markdown syntax for its children recursively. Within the Markdown component you may also use plain HTML or any other type of component that is supported by Astro.

---
// For now, this import _must_ be named "Markdown" and _must not_ be wrapped with a custom component
// We're working on easing these restrictions!
import Markdown from 'astro/components/Markdown.astro';
import Layout from '../layouts/main.astro';
import MyFancyCodePreview from '../components/MyFancyCodePreview.tsx';

const expressions = 'Lorem ipsum';
---

<Layout>
  <Markdown>
    # Hello world!

    **Everything** supported in a `.md` file is also supported here!

    There is _zero_ runtime overhead.

    In addition, Astro supports:
    - Astro {expressions}
    - Automatic indentation normalization
    - Automatic escaping of expressions inside code blocks

    ```jsx
      // This content is not transformed!
      const object = { someOtherValue };
    ```

    - Rich component support like any `.astro` file!
    - Recursive Markdown support (Component children are also processed as Markdown)

    <MyFancyCodePreview:visible>
      ```jsx
      const object = { someOtherValue };
      ```
    </MyFancyCodePreview:visible>
  </Markdown>
</Layout>

Remote Markdown

If you have Markdown in a remote source, you may pass it directly to the Markdown component through the content attribute. For example, the example below fetches the README from Snowpack's GitHub repository and renders it as HTML.

---
import Markdown from 'astro/components/Markdown.astro';

const content = await fetch('https://raw.githubusercontent.com/snowpackjs/snowpack/main/README.md').then(res => res.text());
---

<Layout>
  <Markdown content={content} />
</Layout>

Some times you might want to combine dynamic markdown with static markdown. You can nest Markdown components to get the best of both worlds.

---
import Markdown from 'astro/components/Markdown.astro';

const content = await fetch('https://raw.githubusercontent.com/snowpackjs/snowpack/main/README.md').then(res => res.text());
---

<Layout>
  <Markdown>
    ## Markdown example

    Here we have some __Markdown__ code. We can also dynamically render content from remote places.

    <Markdown content={content} />
  </Mardown>
</Layout>

Security FAQs

Aren't there security concerns to rendering remote markdown directly to HTML?

Yes! Just like with regular HTML, improper use the <Markdown> component can open you up to a cross-site scripting (XSS) attack. If you are rendering untrusted content, be sure to santize your content before rendering it.

Why not use a prop like React's dangerouslySetInnerHTML={{ __html: content }}?

Rendering a string of HTML (or Markdown) is an extremely common use case when rendering a static site and you probably don't need the extra hoops to jump through. Rendering untrusted content is always dangerous! Be sure to santize your content before rendering it.

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