This reverts commit c99d507f.

Refactor Active Record test connection setup. Please see the RUNNING_UNIT_TESTS file for details, but essentially you can now configure things in test/config.yml. You can also run tests directly via the command line, e.g. ruby path/to/test.rb (no rake needed, uses default db connection from test/config.yml). This will help us fix the CI by enabling us to isolate the different Rails versions to different databases.

Split AssociationProxy into an Association class (and subclasses) which manages the association, and a CollectionProxy class which is *only* a proxy. Singular associations no longer have a proxy. See CHANGELOG for more.

Remove undocumented feature from has_one where you could pass false as the second parameter to build_assoc or create_assoc, and the existing associated object would be untouched (the foreign key would not be nullified, and it would not be deleted). If you want behaviour similar to this you can do the following things:

* Use :dependent => :nullify (or don't specify :dependent) if you want to prevent the existing associated object from being deleted
* Use has_many if you actually want multiple associated objects
* Explicitly set the foreign key if, for some reason, you really need to have multiple objects associated with the same has_one. E.g.

    previous = obj.assoc
    obj.create_assoc
    previous.update_attributes(:obj_id => obj.id)

[#4645 state:resolved]
Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Make polymorphic_inverse_of in Reflection throw an InverseOfAssociationNotFoundError if the supplied class doesn't have the appropriate association. [#3520 state:resolved]
Signed-off-by: NEloy Duran <eloy.de.enige@gmail.com>

Provide a slightly more robust we_can_set_the_inverse_on_this? method for polymorphic belongs_to associations. [#3520 state:resolved]

Also add a new test for polymorphic belongs_to that test direct accessor assignment, not just .replace assignment.
Signed-off-by: NEloy Duran <eloy.de.enige@gmail.com>

Signed-off-by: NEloy Duran <eloy.de.enige@gmail.com>

Get rid of a duplicate set_inverse_instance call if you use new_record(true) (e.g. you want to replace the existing instance).
Signed-off-by: NEloy Duran <eloy.de.enige@gmail.com>

Signed-off-by: NEloy Duran <eloy.de.enige@gmail.com>

Signed-off-by: NMichael Koziarski <michael@koziarski.com>

Signed-off-by: NMichael Koziarski <michael@koziarski.com>

You can now add an :inverse_of option to has_one, has_many and belongs_to associations.  This is best described with an example:

class Man < ActiveRecord::Base
  has_one :face, :inverse_of => :man
end

class Face < ActiveRecord::Base
  belongs_to :man, :inverse_of => :face
end

m = Man.first
f = m.face

Without :inverse_of m and f.man would be different instances of the same object (f.man being pulled from the database again).  With these new :inverse_of options m and f.man are the same in memory instance.

Currently :inverse_of supports has_one and has_many (but not the :through variants) associations.  It also supplies inverse support for belongs_to associations where the inverse is a has_one and it's not a polymorphic.
Signed-off-by: NMurray Steele <muz@h-lame.com>
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>