feature: allow custom hook name

[giulianok]

The goal with this PR is to be able to change the hook created by the plugin, for example, being able to execute the code on preHandler rather than onRequest.

I currently have a case where I need to build a redux store on preHandler, injected into the request object for later consuption, and use it in this plugin to perform some checks

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[climba03003]

Please do not change the default. Otherwise, it is a breaking change.

[Uzlopak]

Dont name it handler. Name it addCorsHeaders or so.

[giulianok]

gonna call it addCorsHeadersHandler since there's a function already named addCorsHeaders, and the word handler is good to have since it's mainly called from a hook handler (like onRequest)

[Uzlopak]

Were do we define the variable hookName?

[giulianok]

it's being passed as parameter and defaults to defaultHookName

[Uzlopak]

I dont see a const hookName= in your new code?!

[Uzlopak]

We should call it not hookName but simply hook as we do it in other plugins, like in fastify-rate-limit

[mcollina]

LGTM

[Uzlopak]

Something strange:

If I add a test case like this:

test('Should support custom hook with dynamic config', t => {
  t.plan(22)

  const configs = [{
    origin: 'example.com',
    methods: 'GET',
    credentials: true,
    exposedHeaders: ['foo', 'bar'],
    allowedHeaders: ['baz', 'woo'],
    maxAge: 123
  }, {
    origin: 'sample.com',
    methods: 'GET',
    credentials: true,
    exposedHeaders: ['zoo', 'bar'],
    allowedHeaders: ['baz', 'foo'],
    maxAge: 321
  }]

  const fastify = Fastify()
  let requestId = 0
  const configDelegation = function (req, cb) {
    // request should have id
    t.ok(req.id)
    // request should not have send
    t.notOk(req.send)
    const config = configs[requestId]
    requestId++
    if (config) {
      cb(null, config)
    } else {
      cb(new Error('ouch'))
    }
  }
  fastify.register(cors, {
    delegator: configDelegation
  })

  fastify.addHook('onRequest', (request, reply, done) => {
    t.equal(request[kFastifyContext].preHandler, null)
    t.equal(request[kFastifyContext].onRequest.length, 2)
    done()
  })

  fastify.get('/', (req, reply) => {
    reply.send('ok')
  })

  fastify.inject({
    method: 'GET',
    url: '/'
  }, (err, res) => {
    t.error(err)
    delete res.headers.date
    t.equal(res.statusCode, 200)
    t.equal(res.payload, 'ok')
    t.match(res.headers, {
      'access-control-allow-origin': 'example.com',
      vary: 'Origin',
      'access-control-allow-credentials': 'true',
      'access-control-expose-headers': 'foo, bar',
      'content-length': '2'
    })
  })

  fastify.inject({
    method: 'OPTIONS',
    url: '/',
    headers: {
      'access-control-request-method': 'GET',
      origin: 'example.com'
    }
  }, (err, res) => {
    t.error(err)
    delete res.headers.date
    t.equal(res.statusCode, 204)
    t.equal(res.payload, '')
    t.match(res.headers, {
      'access-control-allow-origin': 'sample.com',
      vary: 'Origin',
      'access-control-allow-credentials': 'true',
      'access-control-expose-headers': 'zoo, bar',
      'access-control-allow-methods': 'GET',
      'access-control-allow-headers': 'baz, foo',
      'access-control-max-age': '321',
      'content-length': '0'
    })
  })

  fastify.inject({
    method: 'GET',
    url: '/',
    headers: {
      'access-control-request-method': 'GET',
      origin: 'example.com'
    }
  }, (err, res) => {
    t.error(err)
    t.equal(res.statusCode, 500)
  })
})

then the unit tests break.

[Uzlopak]

Please dont merge. I will have to review it.

[climba03003]

the unit tests break.

Your OPTIONS assertion is wrong. It will not add CORS header when origin do not match. So, it will block by default.

[Uzlopak]

Well. I reworked it to handle custom hooks more resilient. It is easy to oversee that some hooks also have payload as an parameter.

@climba03003
@mcollina
@Eomm
Please review again.

I modified it heavily.

[mcollina]

lgtm