Hey there!

Related to #41 and #85, I ran into a lot of confusion trying to sort out what the format should be for the request body to a local background function.

In production a background function has the following for the first parameter:

{ @type: 'type.googleapis.com/google.pubsub.v1.PubsubMessage',
  attributes: null,
  data:  '<base64 data>' }

and the following for the "context" parameter:

{ eventId: '749799261766789',
  timestamp: '2019-09-17T19:56:09.018Z',
  eventType: 'providers/cloud.pubsub/eventTypes/topic.publish',
  resource: '<pubsub topic>' }

The current docs for using the functions framework for events suggests curling data in a format that results in the parameters not matching the above - the first parameter becomes:

{ message:
   { attributes: {},
     data: '<base64 data>',
     messageId: '136969346945' },
  subscription: 'projects/myproject/subscriptions/mysubscription' }

And the "context" parameter:

{ type: 'true',
  specversion: 'true',
  source: 'true',
  id: 'true' }

Digging into the source code,

{ data:
  { data: '<base64 data>`,
    attributes: null,
    @type: 'type.googleapis.com/google.pubsub.v1.PubsubMessage' },
  eventId: 749799261766789 }

(Further evidence this is expected is in this WIP branch for NodeJS samples.)

Using the above POST body seems to result in function parameters that most closely match production, and although it doesn't match the POST body for push messages I'm assuming that's what users should send if they want their function to act closest to what they will see when they deploy to Cloud Functions.

Is this correct?