Implement DataPackage class

[roll]

Overview

async DataPackage(descriptor, profile='base', raise_invalid=True, remote_profiles=False)
    valid -> bool
    errors -> list
    descriptor -> dict
    update(**values)
    add_resource(descriptor)
    resources -> Resource[]

Tasks

• [x] implement stub DataPackage class wich could be instantiated as Promise
• [x] add constructor method to store all arguments as internal state
  • [x] descriptor could be javascript object OR
  • [x] descriptor could be a link to json file (local or remote)
  • [x] call validate(descriptor) in constructor to validate datapackage descriptor
  • [x] if raise_invalid raise on invalid
  • [x] if not raise_invalid don't raise on invalid just store errors internally
• [x] implement datapackage.valid getter (always true if raise_invalid is true otherwise depends on validatation result)
• [x] implement datapackage.errors getter (always empty array if raise_invalid is true otherwise list of validation errors)
• [x] implement descriptor getter
• [x] implement update method
  • [x] merge provided object to descriptor and re-validate (use raise_invalid logic here also)
  • [x] raise an error if user trying to alter resources key
• [x] implement resources getter returning array of earlier implemented Resource instances
• [x] implement add_resource method
  • [x] should update descriptor
  • [x] should update resources
  • [x] should trigger datapackage revalidation (use raise_invalid logic here also)
• [ ] write comprehensive tests using data dir (real datapackage descriptors)

[dumyan]

@roll I'm curious about this

implement datapackage.errors getter (always empty array if raise_invalid is true otherwise list of validation errors)

Why should we hide the errors on raise_invalid? I think it would be better to show the errors if the consumer asks for them, just not raising any errors and allowing working with a invalid datapackage will be enough I think for raise_invalid.

[roll]

@dumyan We don't need to hide if raise_invalid = true, constructor or mutator must throw validation error. It means it's not possible to reach state with both (raise_invalid and instance with errors). It's mutual exclusive.