Support constraints when registering plugins

[ghost]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the feature has not already been requested

🚀 Feature Proposal

When registering a plugin, you can currently pass a prefix that apply to all routes in the plugin. It'd be awesome to have that same functionality, but with a version or host constraint instead of a path prefix. I don't believe there is a simple way to do this at the moment without manually passing through options to every route, but I'd love to be wrong!

Motivation

We have a few subdomain specific APIs within our app, so rather than manually passing through options to the plugin and then passing them into each route within the plugin, it'd be really nice to simply set a constraint when registering the plugin itself and have all the routes within the plugin inherit it.

Example

fastify.register(require('./routes/v1/users'), { prefix: '/v1' }) // currently supported
fastify.register(require('./routes/v1/users'), { constraints: { host: 'auth.fastify.io' } }) // not supported

fastify.register(require('./routes/apple'), { constraints: { host: 'apple.fastify.io' } })
fastify.register(require('./routes/berry'), { constraints: { host: 'berry.fastify.io' } })

GET https://apple.fastify.io/
  200 => I LOVE APPLES

GET https://berry.fastify.io/
  200 => I LOVE BERRIES

[mcollina]

This would be awesome to add. Would you like to send a PR?

[ghost]

I'm slammed this month, but I can definitely take a stab hopefully sometime early February. Do you have any pointers or guidance on where or how it should be implemented? Would it work similar to how the prefixes work, or do you think it would be different? Or would we want to implement it in a more generic way so you could actually pass any route options during register versus specific ones (I don't know if that would actually make sense or even work :P)?

[Eomm]

This is already doable within a plugin that listens for the onRoute hook and add the constraints property when necessary.

fastify.register(function plugin (instance, opts, next) {
  instance.addHook('onRoute', function hook (routeOptions) {
    routeOptions.constraints = { host: 'apple.fastify.io' }
    instance.register(require('./routes/apple'))
  })
  next()
})

fastify.register(function plugin (instance, opts, next) {
  instance.addHook('onRoute', function hook (routeOptions) {
    routeOptions.constraints = { host: 'berry.fastify.io' }
    instance.register(require('./routes/berry'))
  })
  next()
})

I have always been afraid to add new fastify's private field names to the plugin's options object to avoid collisions.

https://www.fastify.io/docs/latest/Reference/Plugins/#plugin-options

[ghost]

@Eomm Very interesting! I've actually never used the onRoute hook before, so never even occurred to me that was possible. Would this be seen as the "official" or recommended way of doing it, or is this still slightly a hack? I think it'd still be a cool feature to have for simplicity sake, but this is also still lightweight / easy to understand, so I could also see leaving this in userland and not adding to core. Thanks :)

EDIT: To clarify, does the register for the route also need to happen within the hook, or can it happen outside but within the same scope? e.g.

fastify.register(async function plugin (instance) {
  instance.addHook('onRoute', function hook (routeOptions) {
    routeOptions.constraints = { host: 'berry.fastify.io' }
  })
  instance.register(require('./routes/berry'))
})

[mcollina]

Good spot! All of this could a also be automated with a combo of onRegister and onRoute. It looks like it is a good plugin to be developed.

[Eomm]

is this still slightly a hack?

Not at all: it is the infinite possibilities fastify offers

EDIT: To clarify, does the register for the route also need to happen within the hook, or can it happen outside but within the same scope? e.g.

Yes, it must be the same scope (using the fastify-plugin module if necessary)

[cesarvspr]

Are we sure that we need a new plugin for this? So this means new repo right?
How can we move forward with this? I am willing to help
@climba03003

[climba03003]

Are we sure that we need a new plugin for this?

Yes

So this means new repo right?

Yes, most likely this would be a community plugin.

How can we move forward with this?

Create the plugin, submit PR for adding it as community plugin.

[Ceres6]

Hi!

I'm currently working on creating the mentioned plugin and will submit a PR to add it to community plugins as soon as it's working

[simoneb]

@Eomm @climba03003 you may want to take a look at the implementation we're putting together here nearform/fastify-constraints#1

[Ceres6]

Hi! We have released v1.0.0 of nearform/fastify-constraints. Maybe you can check it to decide if it resolves this issue.

[climba03003]

@Ceres6
Next step should be send a PR here and update https://github.com/fastify/fastify/blob/main/docs/Guides/Ecosystem.md

[Ceres6]

@climba03003
Done!