Separate filtering from reference extraction

[wildmaples]

We currently extract + filter references all in one step, which can sometimes be a point of confusion.

In particular, we do a lot of filtering:

packwerk/lib/packwerk/reference_extractor.rb

Lines 50 to 71 in c6b06b8

	def reference_from_constant(constant_name, node:, ancestors:, file_path:)
	namespace_path = Node.enclosing_namespace_path(node, ancestors: ancestors)
	return if local_reference?(constant_name, Node.name_location(node), namespace_path)
	constant =
	@context_provider.context_for(
	constant_name,
	current_namespace_path: namespace_path
	)
	return if constant&.package.nil?
	relative_path =
	Pathname.new(file_path)
	.relative_path_from(@root_path).to_s
	source_package = @context_provider.package_from_path(relative_path)
	return if source_package == constant.package
	Reference.new(source_package, relative_path, constant)
	end

You can see we remove

• locally referenced constants,
• references to constants packwerk is unable to resolve, or unable to resolve to a package, and
• references to constants in the same package as the source package of the reference.

There could be a light refactor here so that we can extract all references, followed by another layer to do the filtering. It should lend itself to easier testing and a lighter set of test suites.