process-warning

A small utility for generating consistent warning objects across your codebase. It also exposes a utility for emitting those warnings, guaranteeing that they are issued only once (unless configured otherwise).

This module is used by the Fastify framework and it was called fastify-warning prior to version 1.0.0.

Install

npm i process-warning

Usage

The module exports a builder function that returns a utility for creating warnings and emitting them.

const warning = require('process-warning')()

Methods

warning.create(name, code, message[, options])

• name (string, required) - The error name, you can access it later with error.name. For consistency, we recommend prefixing module error names with {YourModule}Warning
• code (string, required) - The warning code, you can access it later with error.code. For consistency, we recommend prefixing plugin error codes with {ThreeLetterModuleName}_, e.g. FST_. NOTE: codes should be all uppercase.
• message (string, required) - The warning message. You can also use interpolated strings for formatting the message.
• options (object, optional) - Optional options with the following properties:
  • unlimited (boolean, optional) - Should the warning be emitted more than once? Defaults to false.

The utility also contains an emit function that you can use for emitting the warnings you have previously created by passing their respective code. A warning is guaranteed to be emitted only once.

warning.emit(code [, a [, b [, c]]])

• code (string, required) - The warning code you intend to emit.
• [, a [, b [, c]]] (any, optional) - Parameters for string interpolation.

const warning = require('process-warning')()
warning.create('FastifyWarning', 'FST_ERROR_CODE', 'message')
warning.emit('FST_ERROR_CODE')

How to use an interpolated string:

const warning = require('process-warning')()
warning.create('FastifyWarning', 'FST_ERROR_CODE', 'Hello %s')
warning.emit('FST_ERROR_CODE', 'world')

The module also exports an warning.emitted Map, which contains all the warnings already emitted. Useful for testing.

const warning = require('process-warning')()
warning.create('FastifyWarning', 'FST_ERROR_CODE', 'Hello %s')
console.log(warning.emitted.get('FST_ERROR_CODE')) // false
warning.emit('FST_ERROR_CODE', 'world')
console.log(warning.emitted.get('FST_ERROR_CODE')) // true

How to use an unlimited warning:

const warning = require('process-warning')()
warning.create('FastifyWarning', 'FST_ERROR_CODE', 'Hello %s', { unlimited: true })
warning.emit('FST_ERROR_CODE', 'world') // will be emitted
warning.emit('FST_ERROR_CODE', 'world') // will be emitted again

License

Licensed under MIT.