prefer-ts-expect-error
Enforce using
@ts-expect-errorover@ts-ignore.
Some problems reported by this rule are automatically fixable by the --fix ESLint command line option.
This rule has been deprecated in favor of @typescript-eslint/ban-ts-comment.
This rule (@typescript-eslint/prefer-ts-expect-error) will be removed in a future major version of typescript-eslint.
When it was first created, @typescript-eslint/ban-ts-comment rule was only responsible for suggesting to remove @ts-ignore directive.
It was later updated to suggest replacing @ts-ignore with @ts-expect-error directive, so that it replaces @typescript-eslint/prefer-ts-expect-error entirely.
TypeScript allows you to suppress all errors on a line by placing a comment starting with @ts-ignore or @ts-expect-error immediately before the erroring line.
The two directives work the same, except @ts-expect-error causes a type error if placed before a line that's not erroring in the first place.
This means it's easy for @ts-ignores to be forgotten about, and remain in code even after the error they were suppressing is fixed.
This is dangerous, as if a new error arises on that line it'll be suppressed by the forgotten about @ts-ignore, and so be missed.
- Flat Config
- Legacy Config
export default tseslint.config({
rules: {
"@typescript-eslint/prefer-ts-expect-error": "error"
}
});
module.exports = {
"rules": {
"@typescript-eslint/prefer-ts-expect-error": "error"
}
};
Try this rule in the playground ↗
Examples
This rule reports any usage of @ts-ignore, including a fixer to replace with @ts-expect-error.
- ❌ Incorrect
- ✅ Correct
// @ts-ignore
const str: string = 1;
/**
* Explaining comment
*
* @ts-ignore */
const multiLine: number = 'value';
/** @ts-ignore */
const block: string = 1;
const isOptionEnabled = (key: string): boolean => {
// @ts-ignore: if key isn't in globalOptions it'll be undefined which is false
return !!globalOptions[key];
};
// @ts-expect-error
const str: string = 1;
/**
* Explaining comment
*
* @ts-expect-error */
const multiLine: number = 'value';
/** @ts-expect-error */
const block: string = 1;
const isOptionEnabled = (key: string): boolean => {
// @ts-expect-error: if key isn't in globalOptions it'll be undefined which is false
return !!globalOptions[key];
};
Options
This rule is not configurable.
When Not To Use It
If you are compiling against multiple versions of TypeScript and using @ts-ignore to ignore version-specific type errors, this rule might get in your way.
You might consider using ESLint disable comments for those specific situations instead of completely disabling this rule.