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