Disallow implicit any error parameters in catchError, subscribe, and tap (rxjs-x/no-implicit-any-catch)

February 11, 2026 · View on GitHub

💼 This rule is enabled in the following configs: ✅ recommended, 🔒 strict.

🔧💡 This rule is automatically fixable by the --fix CLI option and manually fixable by editor suggestions.

💭 This rule requires type information.

This rule requires an explicit type annotation for error parameters in error handlers for catchError, subscribe, and tap. It's similar to the typescript-eslint use-unknown-in-catch-callback-variable rule or the TSConfig useUnknownInCatchVariables option, but is for observables - not try/catch statements.

Rule details

Examples of incorrect code for this rule:

import { catchError, throwError } from "rxjs";

throwError(() => new Error("Kaboom!")).pipe(
  catchError((error) => console.error(error))
);

import { throwError } from "rxjs";

throwError(() => new Error("Kaboom!")).subscribe({
  error: (error) => console.error(error)
});

import { tap, throwError } from "rxjs";

throwError(() => new Error("Kaboom!")).pipe(
  tap({
    error: (error) => console.error(error),
  }),
);

Examples of correct code for this rule:

import { catchError, throwError } from "rxjs";

throwError(() => new Error("Kaboom!")).pipe(
  catchError((error: unknown) => console.error(error))
);

import { throwError } from "rxjs";

throwError(() => new Error("Kaboom!")).subscribe({
  error: (error: unknown) => console.error(error)
});

import { tap, throwError } from "rxjs";

throwError(() => new Error("Kaboom!")).pipe(
  tap({
    error: (error: unknown) => console.error(error),
  }),
);

// With allowExplicitError option:
throwError(() => new Error("Kaboom!")).pipe(
  catchError((error: Error) => console.error(error))
);

Options

NameDescriptionTypeDefault
allowExplicitAnyAllow error variable to be explicitly typed as any.Booleantrue
allowExplicitErrorAllow narrowing error type to Error.Booleanfalse

This rule accepts a single option which is an object with the following properties:

  • allowExplicitAny: Determines whether or not the error variable can be explicitly typed as any. By default, the use of explicit any is allowed.
  • allowExplicitError: Determines whether the error parameter can be narrowed to the Error type. By default, narrowing to Error is not allowed.
{
  "rxjs-x/no-implicit-any-catch": [
    "error",
    { 
      "allowExplicitAny": true,
      "allowExplicitError": true
    }
  ]
}

Warning

The allowExplicitError option is inherently unsafe. The JavaScript throw statement can be followed by any kind of expression, and so catch (e) can provide anything instead of just Error; annotating the error as anything except unknown is technically incorrect.

However, allowExplicitError is convenient in codebases where throw is known to only receive Error objects. We highly recommend you use the only-throw-error rule from typescript-eslint, as well as throw-error from this plugin. Note this also assumes that 3rd-party libraries also only throw Error.

When Not To Use It

If your codebase is not yet able to enable useUnknownInCatchVariables, it likely would be similarly difficult to enable this rule.

Type checked lint rules are more powerful than traditional lint rules, but also require configuring type checked linting.

Further reading

Resources