Implement for_packages_append on Resource

[JonoYang]

We are updating the application package scanning process on scancode.io in nexB/scancode.io#447. We are implementing the package assembly step from scancode-toolkit in scancode.io. The assembly methods from packagedcode associates Resources to packages by appending the package_uid to the for_packages attribute on Resources. This method of associating Resources to Packages does not work on scancode.io because for_packages is an property on CodebaseResource that generates a list of purls from DiscoveredPackages associated with a CodebaseResource.

A solution would be to create a method on the Resource class named for_packages_append that appends a package_uid to Resource.for_packages. This extra level of indirection allows us to create a different implementation on CodebaseResource for associating Packages to Resources using the same interface.

[pombredanne]

re:

A solution would be to create a method on the Resource class named for_packages_append that appends a package_uid to Resource.for_packages

This can work.

An alternative could be use a new Codebase argument that would be the Resource class to use... today this class is crafted based on the provided attributes

commoncode/src/commoncode/resource.py

Line 402 in d3eed9a

def _build_resource_class(self, *args, **kwargs):

Another possibility could be to add and pass a add_to_package(resource, ...) method as an argument to the assemble(..., package_adder=add_to_package, ...) functions?
With a default that would be using a list-backed implementation... and then in SCIO you would have a Django db-backed implmentation of the same function and you would call it when you call assemble?

[JonoYang]

Another possibility could be to add and pass a add_to_package(resource, ...) method as an argument to the assemble(..., package_adder=add_to_package, ...) functions?
With a default that would be using a list-backed implementation... and then in SCIO you would have a Django db-backed implmentation of the same function and you would call it when you call assemble?

I like this approach better than the one I posted before. It makes more sense to pass in the package adding function as an argument into assemble than to add a method to Resource that deals with an attribute that may not be there.

[pombredanne]

This has been implemented and merged in nexB/scancode-toolkit#3035
Thanks!