@beoe/remark-code-hook

Remark plugin to make it easier to write custom processors for code e.g.:

Block-code:

```js
const x = 1;
```

Inline-code:
`x`

This plugin is usefull if you want to create remark plugin to:

• do what you would typically do at rehype level, but can't:
  • highlight code, like @shikijs/rehype, rehype-prism, rehype-highlight etc.
  • render diagrams, like rehype-mermaid
  • do something else, like rehype-color-chips
• do something like obsidian-dataview

Usage

Basic example looks like this:

import { remarkCodeHook } from "@beoe/remark-code-hook";
import { generateSvg } from "./generateSvg.js";

export const rehypeExampleDiagram = (options = {}) => {
  return remarkCodeHook({
    ...options,
    code: ({ code }) => generateSvg(code),
  });
};

If you have code like this:

```js {1,10}
const x = 1;
```

code callback would be called with:

{
  code: "const x = 1;\n",
  inline: false,
  language: "js",
  meta: "{1,10}"
}

If you have code like this:

`const x = 1;`

code callback would be called with:

{
  code: "const x = 1;",
  inline: true,
  language: undefined,
  meta: undefined
}

Now it is time to render your thing:

• you can check code, inline, language, meta and if this is not the block you are looking for you can return undefined - and block would be unchanged
• if you decided to render something you can return string (for example SVG or HTML), you can return MDAST fragment or you can return promise of string or MDAST
  • if return value is MDAST fragment it will replace whole code block
  • if return value is string it would be interpreted as raw-html and will replace whole code block
  • if return value is promise it will wait until it resolves and do one of steps above

You can configure your plugin to be called only for specific cases, for example:

• only for language example: remarkCodeHook({language: "example",..})
• only for inline code: remarkCodeHook({inline: true,..})

To enable caching you need to pass Map-like storage:

remarkCodeHook({ code, cache: new Map(), hashTostring: true });

I checked it with @beoe/cache, but it suppose to work with any storage that has Map like interface. You may pass additional salt param to reset cache, for example when configuration of your plugin changed.

Tips

Meta string

If you need to parse meta param you can use, for example:

• https://github.com/Microflash/fenceparser
• https://github.com/frencojobs/fenceparser

Raw HTML

If you want to return raw HTML in plugin you would need to use:

• .use(remarkRehype, { allowDangerousHtml: true })
• .use(rehypeRaw)