remark-lint-fenced-code-flag

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

Contents

• What is this?
• When should I use this?
• Presets
• Install
• Use
• API
  • unified().use(remarkLintFencedCodeFlag[, options])
  • 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.

When should I use this?

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

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 from 'https://esm.sh/remark-lint-fenced-code-flag@4'

In browsers with esm.sh:

<script type="module">
  import remarkLintFencedCodeFlag 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 no identifiers. It exports the TypeScript type Options. The default export is remarkLintFencedCodeFlag.

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

Warn when language flags of fenced code are not used.

Parameters

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

Returns

Transform (Transformer from unified).

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.

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