ban-ts-comment.md

ban-ts-comment

Bans @ts-<directive> comments from being used or requires descriptions after directive.

TypeScript provides several directive comments that can be used to alter how it processes files. Using these to suppress TypeScript Compiler Errors reduces the effectiveness of TypeScript overall.

The directive comments supported by TypeScript are:

// @ts-expect-error
// @ts-ignore
// @ts-nocheck
// @ts-check

Rule Details

This rule lets you set which directive comments you want to allow in your codebase. By default, only @ts-check is allowed, as it enables rather than suppresses errors.

The configuration looks like this:

interface Options {
  'ts-expect-error'?: boolean | 'allow-with-description';
  'ts-ignore'?: boolean | 'allow-with-description';
  'ts-nocheck'?: boolean | 'allow-with-description';
  'ts-check'?: boolean | 'allow-with-description';
  minimumDescriptionLength?: number;
}

const defaultOptions: Options = {
  'ts-expect-error': 'allow-with-description',
  'ts-ignore': true,
  'ts-nocheck': true,
  'ts-check': false,
  minimumDescriptionLength: 3,
};

ts-expect-error, ts-ignore, ts-nocheck, ts-check directives

A value of true for a particular directive means that this rule will report if it finds any usage of said directive.

❌ Incorrect

if (false) {
  // @ts-ignore: Unreachable code error
  console.log('hello');
}
if (false) {
  /*
  @ts-ignore: Unreachable code error
  */
  console.log('hello');
}

✅ Correct

if (false) {
  // Compiler warns about unreachable code error
  console.log('hello');
}

allow-with-description

A value of 'allow-with-description' for a particular directive means that this rule will report if it finds a directive that does not have a description following the directive (on the same line).

For example, with { 'ts-expect-error': 'allow-with-description' }:

❌ Incorrect

if (false) {
  // @ts-expect-error
  console.log('hello');
}
if (false) {
  /* @ts-expect-error */
  console.log('hello');
}

✅ Correct

if (false) {
  // @ts-expect-error: Unreachable code error
  console.log('hello');
}
if (false) {
  /*
  @ts-expect-error: Unreachable code error
  */
  console.log('hello');
}

minimumDescriptionLength

Use minimumDescriptionLength to set a minimum length for descriptions when using the allow-with-description option for a directive.

For example, with { 'ts-expect-error': 'allow-with-description', minimumDescriptionLength: 10 } the following pattern is:

❌ Incorrect

if (false) {
  // @ts-expect-error: TODO
  console.log('hello');
}

✅ Correct

if (false) {
  // @ts-expect-error The rationale for this override is described in issue #1337 on GitLab
  console.log('hello');
}

When Not To Use It

If you want to use all of the TypeScript directives.

Further Reading

• TypeScript Type Checking JavaScript Files

Related To

• TSLint: ban-ts-ignore

Attributes

• Configs:
  • ✅ Recommended
  • 🔒 Strict
• 🔧 Fixable
• 💭 Requires type information