remark-lint-fenced-code-flag-case

3.0.0 verified Fri May 01 auth: no javascript

remark-lint rule to warn when fenced code blocks have an inconsistently-cased language flag. Current stable version is 3.0.0, released as part of the unified-utils monorepo. Release cadence is irregular, with breaking changes tied to minimum node version bumps (now 20.18.0). Key differentiator: unlike similar lint rules, this enforces lowercase flags to ensure compatibility with tools like Prettier that may ignore uppercase or mixed-case flags. Full Unicode support is included. ESM-only, cannot be required with CommonJS.

Common errors

error Error: Cannot find module 'remark-lint-fenced-code-flag-case' ↓

cause Package not installed or not in node_modules.

fix

Run npm install --save-dev remark-lint-fenced-code-flag-case.

error SyntaxError: The requested module 'remark-lint-fenced-code-flag-case' does not provide an export named 'default' ↓

cause Using an incorrect import syntax or trying to import named exports that don't exist.

fix

Use import lintFencedCodeFlagCase from 'remark-lint-fenced-code-flag-case' (default import).

error TypeError: remark().use is not a function ↓

cause Forgetting to create a remark instance with `remark()`.

fix

Use import { remark } from 'remark'; then call remark().use(...).

Warnings

breaking Minimum supported Node.js version is now 20.18.0 ↓

fix Upgrade Node.js to v20.18.0 or later, or stay on v2.x.

breaking Package is ESM-only and cannot be require()'d ↓

fix Use import syntax; if using CommonJS, use dynamic import().

deprecated Shorthand plugin names in .remarkrc.js may not work in future versions ↓

fix Use full package name 'remark-lint-fenced-code-flag-case' in all configs.

gotcha The rule only checks fenced code blocks that have a language flag; blocks without flags are ignored. ↓

fix No fix needed; this is by design. To require flags, use another rule.

gotcha Mixed-case flags like 'TypeScript' are warned but might still get syntax highlighting; only formatting tools are affected. ↓

fix Lowercase all code block flags to ensure formatting tools work.

Install

npm install remark-lint-fenced-code-flag-case

yarn add remark-lint-fenced-code-flag-case

pnpm add remark-lint-fenced-code-flag-case

Imports

lintFencedCodeFlagCase

wrong

const lintFencedCodeFlagCase = require('remark-lint-fenced-code-flag-case')

correct

import lintFencedCodeFlagCase from 'remark-lint-fenced-code-flag-case'

ESM-only package; require() will fail. Default export is the lint rule function.

remark-lint-fenced-code-flag-case (plugin)
wrong
```
.use('remark-lint-fenced-code-flag-case')
```
correct
```
.use(lintFencedCodeFlagCase)
```
Must pass the imported function, not a string name, to .use().
remarkConfig plugins
wrong
```
"plugins": ["lint-fenced-code-flag-case"]
```
correct
```
"plugins": ["remark-lint-fenced-code-flag-case"]
```
In package.json config, use full package name without prefix; in .remarkrc.js, shorthand is allowed.

Quickstart

Lints a Markdown file for inconsistently-cased fenced code block flags using remark-lint and reports warnings.

import { read } from 'to-vfile';
import { reporter } from 'vfile-reporter';
import { remark } from 'remark';
import remarkLint from 'remark-lint';
import lintFencedCodeFlagCase from 'remark-lint-fenced-code-flag-case';

const file = await remark()
  .use(remarkLint)
  .use(lintFencedCodeFlagCase)
  .process(await read('example.md'));

console.log(reporter(file));