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fastify-plugin

3.0.0 • Public • Published

fastify-plugin

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fastify-plugin is a plugin helper for Fastify.

When you build plugins for Fastify and you want that them to be accessible in the same context where you require them, you have two ways:

  1. Use the skip-override hidden property
  2. Use this module

Note: the v2.x series of this module covers Fastify v3. For Fastify v2 support refert to the v1.x series.

Usage

fastify-plugin can do three things for you:

  • Add the skip-override hidden property
  • Check the bare-minimum version of Fastify
  • Pass some custom metadata of the plugin to Fastify

Example:

const fp = require('fastify-plugin')
 
module.exports = fp(function (fastify, opts, next) {
  // your plugin code
  next()
})

Metadata

In addition if you use this module when creating new plugins, you can declare the dependencies, the name and the expected Fastify version that your plugin needs.

Fastify version

If you need to set a bare-minimum version of Fastify for your plugin, just add the semver range that you need:

const fp = require('fastify-plugin')
 
module.exports = fp(function (fastify, opts, next) {
  // your plugin code
  next()
}, { fastify: '3.x' })

If you need to check the Fastify version only, you can pass just the version string.

You can check here how to define a semver range.

Name

Fastify uses this option to validate dependency graph. On one hand it makes sure that no name collision occurs. On the other hand it makes possible to perform dependency check.

const fp = require('fastify-plugin')
 
function plugin (fastify, opts, next) {
  // your plugin code
  next()
}
 
module.exports = fp(plugin, {
  fastify: '3.x',
  name: 'your-plugin-name'
})

Dependencies

You can also check if the plugins and decorators which your plugin intend to use are present in the dependency graph.

Note: This is the point where registering name of the plugins become important, because you can reference plugin dependencies by their name.

const fp = require('fastify-plugin')
 
function plugin (fastify, opts, next) {
  // your plugin code
  next()
}
 
module.exports = fp(plugin, {
  fastify: '3.x',
  decorators: {
    fastify: ['plugin1', 'plugin2'],
    reply: ['compress']
  },
  dependencies: ['plugin1-name', 'plugin2-name']
})

Bundlers and Typescript

fastify-plugin adds a .default and [name] property to the passed in function. The type definition would have to be updated to leverage this.

Known Issue: TypeScript Contextual Inference

Documentation Reference

It is common for developers to inline their plugin with fastify-plugin such as:

fp((fastify, opts, next) => { next() })
fp(async (fastify, opts) => { return })

TypeScript can sometimes infer the types of the arguments for these functions. Plugins in fastify are recommended to be typed using either FastifyPluginCallback or FastifyPluginAsync. These two definitions only differ in two ways:

  1. The third argument next (the callback part)
  2. The return type FastifyPluginCallback or FastifyPluginAsync

At this time, TypeScript inference is not smart enough to differentiate by definition argument length alone.

Thus, if you are a TypeScript developer please use on the following patterns instead:

// Callback
 
// Assign type directly
const pluginCallback: FastifyPluginCallback = (fastify, options, next) => { }
fp(pluginCallback)
 
// or define your own function declaration that satisfies the existing definitions
const pluginCallbackWithTypes = (fastify: FastifyInstance, options: FastifyPluginOptions, next: (error?: FastifyError) => void): void => { }
fp(pluginCallbackWithTypes)
// or inline
fp((fastify: FastifyInstance, options: FastifyPluginOptions, next: (error?: FastifyError) => void): void => { })
 
// Async
 
// Assign type directly
const pluginAsync: FastifyPluginAsync = async (fastify, options) => { }
fp(pluginAsync)
 
// or define your own function declaration that satisfies the existing definitions
const pluginAsyncWithTypes = async (fastify: FastifyInstance, options: FastifyPluginOptions): Promise<void> => { }
fp(pluginAsyncWithTypes)
// or inline
fp(async (fastify: FastifyInstance, options: FastifyPluginOptions): Promise<void> => { })

Acknowledgements

This project is kindly sponsored by:

License

Licensed under MIT.

Install

npm i fastify-plugin

DownloadsWeekly Downloads

177,329

Version

3.0.0

License

MIT

Unpacked Size

26.3 kB

Total Files

18

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