@selfage/nested_error

Install

npm install @selfage/nested_error

Overview

Written in TypeScript and compiled to ES6 with inline source map & source. See @selfage/tsconfig for full compiler options. Provides a simple implementation to take an error as the cause and output nested stacks with "Caused by: ".

Nested error

Supply an existing error as the cause like the following.

import { NestedError } from '@selfage/nested_error';

throw new NestedError('more context', new Error('Failure'));

It will output the following, omitting some details.

NestedError: more context
    at Object.<anonymous> (.../nested_error/temp.js:4:7)
    ...
Caused by: Error: Failure
    at Object.<anonymous> (.../nested_error/temp.js:4:47)
    ...

Standalone error

You can also create NestedError without a cause.

import { NestedError } from '@selfage/nested_error';

throw new NestedError('some issue');

Any cause

When catching an error, it's often of any type, which can be passed to NestedError without type assertion/casting, i.e., when stack property is not available, it calls toString() to generate the output.

import { NestedError } from '@selfage/nested_error';

try {
  throw 'Failed!';
} catch (e) {
  throw new NestedError('some issue', e);
}

It will output the following, omitting details.

NestedError: some issue
    at Object.<anonymous> (.../nested_error/temp.js:8:11)
    ...
Caused by: Failed!

Subclass

import { NestedError } from '@selfage/nested_error';

class CustomError extends NestedError {
  public constructor(message?: string, cause?: any) {
    super(message, cause);
  }
}

throw new CustomError('more context', new Error('Failure'));

CustomError: more context
    at Object.<anonymous> (.../nested_error/temp.js:9:7)
    ...
Caused by: Error: Failure
    at Object.<anonymous> (.../nested_error/temp.js:9:39)
    ...

Caveats

With ES6, we simply extend native Error class, without fixing issues such as broken prototype chain, and thus could bring compatibility issue to browsers. Use if you don't care.

Class name might be mangled by minification. There is no easy fix unless you exclude them from being mangled. Setting name property in subclasses doesn't help because the constructor of NestedError already finalized stack property at least in case of V8 environment.

Stack trace from TypeScript source file

If you are developing in TypeScript, printing stack trace from TypeScript source file is often desired. One option is to install source-map-support.

import { NestedError } from '@selfage/nested_error';
import 'source-map-support/register';

throw new NestedError('more context', new Error('Failure'));

It will output the following, omitting details.

NestedError: more context
    at Object.<anonymous> (.../nested_error/temp.ts:4:7)
    ...
Caused by: Error: Failure
    at Object.<anonymous> (.../nested_error/temp.ts:4:39)
    ...