Support virtual_attribute => another_attribute

[kbrock]

This is written as a bug, but is probably an RFE. Or at least a request to add a warning.

Overview

For uses clauses, we currently don't support nested attributes:

class Book
  has_and_belongs_to_many :co_authors, :class_name => "Author"
end

class Author
  virtual_has_one :book_with_most_bookmarks, :uses => {:books => :bookmarks}
  virtual_has_many :famous_co_authors, :uses => {:book_with_most_bookmarks => :co_authors} ## HERE
end

Issue

Above, it is not obvious what the value of the includes should be:

• option 1: {:books => {:bookmarks => :co_authors}}
• option 2: {:books => [:bookmarks, :co_authors]}

Currently we ignore the target, so we basically read the definition as the following:

class Author
  virtual_has_many :famous_co_authors, :uses => :book_with_most_bookmarks
end

We currently do not have the need to support this feature, but I noticed it while writing tests for another issue.

Options

We have a few ways to move forward:

• continue ignoring the target
  (developer can write it a different way)
• add a warning
• throw an exception
• look at the klass of the association and determine the best way
  (this involves introspection of another class which has caused class loader deadlocks in the past)

[kbrock]

I'm thinking we should add the warning at the least.
Adding this functionality is complicated and we have been doing fine without it. (then again, since it just eats the issue, we may be running into it)

[Fryguy]

I think a warning is good - at least then we'll see it in our code base.