errorSubclassProperties

Reports incorrect Error subclass definitions that don't follow best practices.

✅ This rule is included in the ts logicalStrict presets.

When creating custom error classes that extend Error, there are several conventions that should be followed to ensure the errors work correctly and are easy to debug.

This rule reports:

• Invalid class names: should be capitalized and end with Error
• Missing name property: required for proper error identification
• Using this.constructor.name: won’t work after minification
• Mismatched name values: should match the class name
• Redundant this.message assignments: already set by super()

Examples

Correct Error Subclass

❌ Incorrect

class foo extends Error {
  constructor(message: string) {
    super(message);
    this.name = "foo";
  }
}

✅ Correct

class FooError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "FooError";
  }
}

Missing Name Property

❌ Incorrect

class CustomError extends Error {
  constructor(message: string) {
    super(message);
  }
}

✅ Correct

class CustomError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "CustomError";
  }
}

Avoid this.constructor.name

❌ Incorrect

class CustomError extends Error {
  constructor(message: string) {
    super(message);
    this.name = this.constructor.name;
  }
}

✅ Correct

class CustomError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "CustomError";
  }
}

Redundant Message Assignment

❌ Incorrect

class CustomError extends Error {
  constructor(message: string) {
    super(message);
    this.message = message;
    this.name = "CustomError";
  }
}

✅ Correct

class CustomError extends Error {
  constructor(message: string) {
    super(message);
    this.name = "CustomError";
  }
}

Options

This rule is not configurable.

When Not To Use It

If you have a specific naming convention for errors that doesn’t follow the standard pattern, or if you’re working with legacy code that can’t be easily refactored, you may need to disable this rule.

Further Reading

• MDN: Error
• Custom errors in JavaScript

Equivalents in Other Linters

• ESLint: unicorn/custom-error-definition