unicorn/custom-error-definition Style
What it does
Enforces the only valid way of Error subclassing. It works with any super class that ends in Error.
Why is this bad?
Incorrectly defined custom errors can lead to unexpected behavior when catching and identifying errors. Missing super() calls, wrong name property values, or non-standard class names make error handling unreliable.
Examples
Examples of incorrect code for this rule:
js
class CustomError extends Error {
constructor(message) {
super(message);
// The `this.message` assignment is useless as it's already set via the `super()` call.
this.message = message;
this.name = "CustomError";
}
}
class CustomError extends Error {
constructor(message) {
super();
// Pass the error message to `super()` instead of setting `this.message`.
this.message = message;
this.name = "CustomError";
}
}
class CustomError extends Error {
constructor(message) {
super(message);
// No `name` property set. The name property is needed so the
// error shows up as `[CustomError: foo]` and not `[Error: foo]`.
}
}
class CustomError extends Error {
constructor(message) {
super(message);
// Use a string literal to set the `name` property as it will not change after minifying.
this.name = this.constructor.name;
}
}
class CustomError extends Error {
constructor(message) {
super(message);
// The `name` property should be set to the class name.
this.name = "MyError";
}
}Examples of correct code for this rule:
js
class CustomError extends Error {
constructor(message) {
super(message);
this.name = "CustomError";
}
}
class CustomError extends Error {
constructor() {
super("My custom error");
this.name = "CustomError";
}
}
class CustomError extends TypeError {
constructor() {
super();
this.name = "CustomError";
}
}
class CustomError extends Error {
name = "CustomError";
}How to use
To enable this rule using the config file or in the CLI, you can use:
json
{
"rules": {
"unicorn/custom-error-definition": "error"
}
}ts
import { defineConfig } from "oxlint";
export default defineConfig({
rules: {
"unicorn/custom-error-definition": "error",
},
});bash
oxlint --deny unicorn/custom-error-definitionVersion
This rule was added in v1.57.0.