micromark-extension-gfm-strikethrough

micromark extensions to support GFM strikethrough.

What is this?
When to use this
Install
Use
API
Authoring
HTML
CSS
Syntax
Types
Compatibility
Security
Related
Contribute
License

What is this?

This package contains extensions that add support for strikethrough as enabled by GFM to micromark.

When to use this

This project is useful when you want to support strikethrough in markdown.

You can use these extensions when you are working with micromark. To support all GFM features, use micromark-extension-gfm.

When you need a syntax tree, you can combine this package with mdast-util-gfm-strikethrough.

All these packages are used remark-gfm, which focusses on making it easier to transform content by abstracting these internals away.

Install

This package is ESM only. In Node.js (version 16+), install with npm:

npm install micromark-extension-gfm-strikethrough

In Deno with esm.sh:

import {gfmStrikethrough, gfmStrikethroughHtml} from 'https://esm.sh/micromark-extension-gfm-strikethrough@2'

In browsers with esm.sh:

<script type="module">
  import {gfmStrikethrough, gfmStrikethroughHtml} from 'https://esm.sh/micromark-extension-gfm-strikethrough@2?bundle'
</script>

Use

import {micromark} from 'micromark'
import {
  gfmStrikethrough,
  gfmStrikethroughHtml
} from 'micromark-extension-gfm-strikethrough'

const output = micromark('Some ~strikethrough~.', {
  extensions: [gfmStrikethrough()],
  htmlExtensions: [gfmStrikethroughHtml()]
})

console.log(output)

Yields:

<p>Some <del>strikethrough</del></p>.

API

This package exports the identifiers gfmStrikethrough and gfmStrikethroughHtml. There is no default export.

The export map supports the development condition. Run node --conditions development module.js to get instrumented dev code. Without this condition, production code is loaded.

`gfmStrikethrough(options?)`

Create an extension for micromark to enable GFM strikethrough syntax.

Parameters

options (Options, optional) — configuration

Returns

Extension for micromark that can be passed in extensions, to enable GFM strikethrough syntax (Extension).

`gfmStrikethroughHtml()`

Create an HTML extension for micromark to support GFM strikethrough when serializing to HTML.

Returns

Extension for micromark that can be passed in htmlExtensions, to support GFM strikethrough when serializing to HTML (HtmlExtension).

`Options`

Configuration (TypeScript type).

Fields

singleTilde (boolean, default: true) — whether to support strikethrough with a single tilde. Single tildes work on github.com, but are technically prohibited by the GFM spec

Authoring

When authoring markdown with strikethrough, it is recommended to use two markers. While github.com allows single tildes too, it technically prohibits it in their spec.

HTML

When tilde sequences match, they together relate to the <del> element in HTML. See § 4.7.2 The del element in the HTML spec for more info.

CSS

GitHub itself does not apply interesting CSS to del elements. It currently (July 2022) does change code in del.

del code {
  text-decoration: inherit;
}

For the complete actual CSS see sindresorhus/github-markdown-css.

Syntax

Strikethrough sequences form with the following BNF:

gfm_attention_sequence ::= 1*'~'

Sequences are matched together to form strikethrough based on which character they contain, how long they are, and what character occurs before and after each sequence. Otherwise they are turned into data.

Types

This package is fully typed with TypeScript. It exports the additional type Options.

Compatibility

Projects maintained by the unified collective are compatible with maintained versions of Node.js.

When we cut a new major release, we drop support for unmaintained versions of Node. This means we try to keep the current release line, micromark-extension-gfm-strikethrough@^2, compatible with Node.js 16.

This package works with micromark version 3 and later.

Security

This package is safe.

micromark-extension-gfm — support all of GFM
mdast-util-gfm-strikethrough — support all of GFM in mdast
mdast-util-gfm — support all of GFM in mdast
remark-gfm — support all of GFM in remark

Contribute

See contributing.md in micromark/.github for ways to get started. See support.md for ways to get help.

This project has a code of conduct. By interacting with this repository, organization, or community you agree to abide by its terms.

License

Not parsing “empty” strikethrough

Subject of the issue

try to roundtrip the following mdast:

root[1]
└─0 heading[4]
    │ depth: 2
    ├─0 text "Hello, "
    ├─1 delete[1]
    │   └─0 text "world."
    ├─2 text " stray "
    └─3 delete[0]

stringify produces:

## Hello, ~~world.~~ stray ~~~~

parsing this again produces:

root[1] (1:1-2:1, 0-32)
└─0 heading[3] (1:1-1:32, 0-31)
    │ depth: 2
    ├─0 text "Hello, " (1:4-1:11, 3-10)
    ├─1 delete[1] (1:11-1:21, 10-20)
    │   └─0 text "world." (1:13-1:19, 12-18)
    └─2 text " stray ~~~~" (1:21-1:32, 20-31)

Your environment

$ npm ls --depth 0
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected]
├── [email protected]
└── [email protected]

Steps to reproduce

const remark = require('remark-parse');
const stringify = require('remark-stringify');
const unified = require('unified');
const gfm = require('remark-gfm');
const inspect = require('unist-util-inspect');
const {
  root,
  text,
  heading,
  strike,
} = require('mdast-builder');

const mdast = root([
  heading(2, [
    text('Hello, '),
    strike(text('world.')),
    text(' stray '),
    strike([])
  ]),
]);

console.log('original:')
console.log(inspect(mdast));

const doc = unified()
  .use(stringify)
  .use(gfm)
  .stringify(mdast);

console.log('markdown:')
console.log(doc);

const mdast2 = unified()
  .use(remark)
  .use(gfm)
  .parse(doc);


console.log('roundtripped:')
console.log(inspect(mdast2));

Expected behavior

the empty strikethrough node should not be lost when reparsing.

Actual behavior

the empty strikethrough node is converted to text.

Workaround

since the empty strikethrough nodes have no semantic meaning, they could be removed from the mdast prior to serialization, or suppressed by gfm-to-markdown automatically.

micromark / micromark-extension-gfm-strikethrough Goto Github PK