remark-lint-fenced-code-flag

remark-lint-fenced-code-flag

remark-lint rule to warn when language flags of fenced code are not used or used incorrectly.

Contents

• What is this?
• When should I use this?
• Presets
• Install
• Use
• API
  • unified().use(remarkLintFencedCodeFlag[, options])
  • checkGithubLinguistFlag(value)
  • CheckFlag
  • Options
• Recommendation
• Examples
• Compatibility
• Contribute
• License

What is this?

This package checks the language flags of fenced code blocks, whether they exist, and optionally what values they hold.

Particularly, it provides a check according to GitHub Linguist. Which is what GitHub uses to highlight code. So you can make sure that the language flags you use are recognized by GitHub (or starry-night)

When should I use this?

You can use this package to check that the style of language flags of fenced code blocks is consistent and known.

Presets

This plugin is included in the following presets:

Preset	Options
remark-preset-lint-markdown-style-guide	{ allowEmpty: false }

Install

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

npm install remark-lint-fenced-code-flag

In Deno with esm.sh:

import remarkLintFencedCodeFlag, {checkGithubLinguistFlag} from 'https://esm.sh/remark-lint-fenced-code-flag@4'

In browsers with esm.sh:

<script type="module">
  import remarkLintFencedCodeFlag, {checkGithubLinguistFlag} from 'https://esm.sh/remark-lint-fenced-code-flag@4?bundle'
</script>

Use

On the API:

import remarkLint from 'remark-lint'
import remarkLintFencedCodeFlag from 'remark-lint-fenced-code-flag'
import remarkParse from 'remark-parse'
import remarkStringify from 'remark-stringify'
import {read} from 'to-vfile'
import {unified} from 'unified'
import {reporter} from 'vfile-reporter'

const file = await read('example.md')

await unified()
  .use(remarkParse)
  .use(remarkLint)
  .use(remarkLintFencedCodeFlag)
  .use(remarkStringify)
  .process(file)

console.error(reporter(file))

On the CLI:

remark --frail --use remark-lint --use remark-lint-fenced-code-flag .

On the CLI in a config file (here a package.json):

 …
 "remarkConfig": {
   "plugins": [
     …
     "remark-lint",
+    "remark-lint-fenced-code-flag",
     …
   ]
 }
 …

API

This package exports the identifier checkGithubLinguistFlag. It exports the TypeScript types CheckFlag and Options. The default export is remarkLintFencedCodeFlag.

unified().use(remarkLintFencedCodeFlag[, options])

Warn when language flags of fenced code are not used.

Parameters

• options (Array<string>, CheckFlag, or Options, optional) — check, configuration, or flags to allow

Returns

Transform (Transformer from unified).

checkGithubLinguistFlag(value)

Check according to GitHub Linguist.

Parameters

• value (string) — language flag to check

Returns

Whether the flag is valid (undefined), or a message to warn about (string).

Returns

Transform (Transformer from unified).

CheckFlag

Custom check (TypeScript type).

Parameters

• value (string) — language flag to check

Returns

Whether the flag is valid (undefined), or a message to warn about (string).

Options

Configuration (TypeScript type).

Fields

• allowEmpty (boolean, default: false) — allow language flags to be omitted
• flags (Array<string>, optional) — flags to allow, other flags will result in a warning

Recommendation

While omitting language flags is fine to signal that code is plain text, it could point to a mistake. It’s recommended to instead use a certain flag for plain text (such as txt) and to turn this rule on. If possible, stick with what is supported by GitHub.

Examples

ok.md

In

Some markdown:

```markdown
# Mercury
```

Out

No messages.

not-ok.md

In

```
mercury()
```

Out

1:1-3:4: Unexpected missing fenced code language flag in info string, expected keyword

ok-allow-empty.md

When configured with { allowEmpty: true }.

In

```
mercury()
```

Out

No messages.

not-ok-allow-empty.md

When configured with { allowEmpty: false }.

In

```
mercury()
```

Out

1:1-3:4: Unexpected missing fenced code language flag in info string, expected keyword

ok-array.md

When configured with [ 'markdown' ].

In

```markdown
# Mercury
```

Out

No messages.

ok-options.md

When configured with { flags: [ 'markdown' ] }.

In

```markdown
# Mercury
```

Out

No messages.

not-ok-array.md

When configured with [ 'markdown' ].

In

```javascript
mercury()
```

Out

1:1-3:4: Unexpected fenced code language flag `javascript` in info string, expected `markdown`

not-ok-long-array.md

When configured with [ 'javascript', 'markdown', 'mdx', 'typescript' ].

In

```html
<h1>Mercury</h1>
```

Out

1:1-3:4: Unexpected fenced code language flag `html` in info string, expected `javascript`, `markdown`, `mdx`, …

not-ok-options.md

When configured with '🌍'.

Out

1:1: Unexpected value `🌍` for `options`, expected array or object

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, remark-lint-fenced-code-flag@4, compatible with Node.js 16.

Contribute

See contributing.md in remarkjs/.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

MIT © Titus Wormer