addParamsForward.js

/*
  Install this hook in app.hooks.js
  
  module.exports = app => {
    app.hooks({
      before: {
        all: [
          addParamsForward()
        ]
      }
    })
  }
  
  Then use whenever you want to forward params, e.g. in a hook:
  
  const { app, params } = context
  app.service('another-service').find({ query: { id: 'x' }, ...params.forward() })
  app.service('another-service').get(id, params.forward())
  app.service('another-service').patch(id, {smth: 'x' }, params.forward())
*/

const { has } = require('lodash')
const paramsSeen = new WeakSet()

module.exports = function addParamsForward() {
  return context => {
    if (paramsSeen.has(context.params)) {
      throw new Error(
        `Params should never be shared across services, always use params.forward(). Fix calls to ${context.path}#${context.method}`,
      )
    }

    paramsSeen.add(context.params)

    context.params.forward = ({ only, omit = [] } = {}) => {
      const { params } = context

      const forwardedParams = {
        caller: {
          path: context.path,
          method: context.method,
          type: context.type,
        },
        requestId: context.params.requestId,
        forwarded: true,
      }

      ;(
        only || [
          'authenticated',
          'user',
          'transaction',
          'skipEvents',
          'permissions',
        ]
      ).forEach(param => {
        if (has(params, param) && !omit.includes(param)) {
          forwardedParams[param] = params[param]
        }
      })

      if (forwardedParams.authenticated) {
        forwardedParams.authentication = params.authentication
      }

      return forwardedParams
    }
  }
}

@KidkArolis,

ah! it works, but still can't figure out why using spread ...params.forward() will trigger the non-callable @@iterator error. Other than that, it looks good now.

If you know what's causing the error, do let me know.

Thanks!

Because you can only spread properties in an object:

let a = { x: 'y' }
let b = { ...a }

Or you can spread arrays as arguments:

let a = ['x', 'y', 'z']
example(...a)

You can't spread an object as arguments:

// not valid!!
// throws non-callable @@iterator / is not iterable
let a = { x: 'y' }
example(...a)

In Feathers, params is an object, params.forward() is also an object, so:

// invalid
service.get(1, ...params)
service.get(1, ...params.forward())

// valid
service.get(1, params)
service.get(1, params.forward())
service.get(1, { ...params })
service.get(1, { ...params.forward() })

// invalid
service.find(...params)
service.find(...params.forward())

// valid
service.find({ query: { email: 'x', }, ...params })
service.find({ query: { email: 'x', }, ...params.forward() })

That's it.

Thank you so much.

Hello @KidkArolis,

I noticed that in the forwardedParams.caller.type is always before, is that intended? I would imagine that it should be whoever called the forward()?

// I have a hook x at the after-remove hook of service y
// now I call to remove
app.service('y').remove(id)

// within hook x, it calls service z (note hook x is in after-remove hook of service y)
app.service('z').remove(anotherId, params.forward());

So when I logs out the forwardedParams before the return in addParamsForward(), the caller.type is before.

@bwgjoseph you're right, it could be fixed by readding addParamsForward() hook in after all, so that it uses updated the closed over context when computing forwardedParams.