@lint-suite/eslint-plugin-one-line-guard

This ESLint plugin keeps compact TypeScript and JavaScript guard clauses visible by requiring a braced if with one return, throw, continue, or break to use an unbraced one-line form when it fits. It leaves guards with an else, comments, additional statements, or multi-line syntax unchanged.

Install

Requires Node.js 24+, ESLint ^10.9.1, and TypeScript >=6.0.3.

pnpm add -D @lint-suite/eslint-plugin-one-line-guard eslint@^10.9.1 typescript@">=6.0.3" typescript-eslint

The plugin does not configure a TypeScript parser. Use typescript-eslint for TypeScript files:

// eslint.config.js
import oneLineGuard from '@lint-suite/eslint-plugin-one-line-guard';
import tseslint from 'typescript-eslint';

export default [{
  files: ['**/*.ts'],
  languageOptions: { parser: tseslint.parser },
  plugins: { oneLineGuard },
  rules: { 'oneLineGuard/one-line-guard': 'error' }
}];

Options

maxLineLength is a positive integer and defaults to 80. The rule measures the completed line including its existing indentation. Examples that use a different limit state it explicitly.

rules: { 'oneLineGuard/one-line-guard': ['error', { maxLineLength: 100 }] }

Examples

Each example is checked by this rule alone, not by an entire ESLint suite.

Valid examples

1. Already unbraced return guard

if (!user) return null;

2. Block with two statements

if (!user) {
  logMissingUser();
  return null;
}

3. Guard with an else

if (!user) {
  return null;
} else {
  return user;
}

4. Guard block containing a comment

if (!user) {
  // Preserve this explanation.
  return null;
}

5. Guard exceeding an explicit 40-column limit

With maxLineLength: 40:

if (ready) {
  return someExtremelyLongIdentifierNameThatOverflowsTheLimit;
}

Invalid examples

1. Braced return guard

if (!user) {
  return null;
}

2. Braced throw guard

if (!valid) {
  throw error;
}

3. Braced continue guard

for (const item of items) {
  if (!item) {
    continue;
  }
}

4. Braced break guard

while (running) {
  if (done) {
    break;
  }
}

5. Guard exactly at an explicit 40-column limit

With maxLineLength: 40:

if (a) {
  return xxxxxxxxxxxxxxxxxxxxxxxxx;
}

The rule automatically fixes reported guards by removing their braces. The named oneLineGuardRule export is for composed plugin registries.