JS.TS.NO.IMPLICIT.ANY.CATCH

TypeScript 4.0 added support for adding an explicit any or unknown type annotation on a catch clause variable.

By default, TypeScript will type a catch clause variable as any, so explicitly annotating it as unknown can add a lot of safety to your codebase.

The noImplicitAny flag in TypeScript does not cover this for backwards compatibility reasons, however you can use useUnknownInCatchVariables (part of strict) instead of this rule.

DEPRECATED

Rule Details

This rule requires an explicit type to be declared on a catch clause variable.

Examples of code for this rule:

<!--tabs-->

Incorrect

try {
  // ...
} catch (e) {
  // ...
}

Correct

<!-- TODO: prettier currently removes the type annotations, re-enable this once prettier is updated --> <!-- prettier-ignore-start -->

try {
  // ...
} catch (e: unknown) {
  // ...
}

<!-- prettier-ignore-end -->

Options

The rule accepts an options object with the following properties:

type Options = {
  // if false, disallow specifying `: any` as the error type as well. See also `no-explicit-any`
  allowExplicitAny: boolean;
};

const defaults = {
  allowExplicitAny: false,
};

allowExplicitAny

The follow is is not considered a warning with { allowExplicitAny: true }

<!-- TODO: prettier currently removes the type annotations, re-enable this once prettier is updated --> <!-- prettier-ignore-start -->

try {
  // ...
} catch (e: any) {
  // ...
}

<!-- prettier-ignore-end -->

When Not To Use It

If you are not using TypeScript 4.0 (or greater), then you will not be able to use this rule, annotations on catch clauses is not supported.

Further Reading

• TypeScript 4.0 Release Notes (https://devblogs.microsoft.com/typescript/announcing-typescript-4-0/#unknown-on-catch)