baptistemarchand / berror

Rich Errors including chain of causes, metadata, easy logging and TypeScript definitions.

BError - Better Error Handling

Inspired by VError and written in TypeScript. Compatible with deno. Zero dependencies.

A BError is just like a regular Error with three added benefits:

Chain of causes

When you create a BError you can provide it with the error that caused it. It doesn't need to be a BError. Any Error will work:

try {
  throw new Error("Something went wrong")
} catch (e) {
  throw new BError("Oops", e)
}
// will create an error with the message: `Oops: Something went wrong`

Metadata

You can add some metadata to your errors to help with debugging:

const path = "/test"
try {
  tryToOpenPath(path)
} catch (e) {
  throw new BError("Could not open path", e, {path})
}
// will create an error with the message:
// `Could not open path: permission denied {path: "/test"}`

The metadata is kept in the chain, the final error will contain all the metadata of the errors that caused it. If two errors send the same metadata property, the last one will override the first one.

If you want to send metadata but you don't have an error that you just caught you can pass undefined or null to the constructor: new BError("Oops", undefined, {foo: 42})

Logging

BError comes with a log function that makes it easy and short to log the error.

  // will log the error using console.error()
  new BError("Something went wrong").log()

Using a custom logger

BError is meant to be extended to integrate your own logger. Just extend the BError class and override the log function to do whatever you want.

Example with winston:

import {BError} from "berror"
import {createLogger, transports} from 'winston'

const logger = createLogger({
  level: 'debug',
  transports: [
    new transports.Console()
  ]
})
  

export class MyError extends BError {
  public log(level: string) {
    if (level === "error") {
      logger.error(this.message, this.metadata)
    } else {
      logger.info(this.message, this.metadata)
    }
  }
}