Make ActiveAdmin ORM agnostic (i.e. works without loading ActiveRecord)

[johnnyshields]

1. Add ORM-specific loaders:

• lib\active_admin\orm\active_record
• lib\active_admin\orm\mongoid

2. Move Comments plugin to ActiveRecord ORM directory. Comments support is AR-only for now.

3. Add ActiveRecord/Mongoid type checks to DisplayHelper#pretty_format(object) method

[zorab47]

What will happen if both ActiveRecord and Mongoid are present?

[johnnyshields]

In that case, both will load. As long as the plugins within the directories don't conflict with each other, should not be a problem. (Currently there are no Mongoid plugins, so no conflicts). We could add a global config option to AA so user can control which set(s) to load.

[johnnyshields]

@daxter committed change as per your request

[seanlinsley]

No, the problem was one of indentation. The code is currently like this:

case foo
  when Bar
    baz
end

When it should be like this:

case foo
when Bar
  baz
end

There was nothing wrong with the nested if statement.

[johnnyshields]

Ah oops. Well, I've now fixed the indentation and I've kept the procs because it looks nicer anyway.

[coveralls]

Coverage decreased (-0.0%) when pulling 94d74ab on johnnyshields:orm-agnosticism into 75de0f1 on gregbell:master.

[seanlinsley]

Okay, looks good. Thanks for taking the time to contribute.

[fred]

Hi,
Master is still trying to load ActiveRecord.
I use mongoid and dont have "active_record/railtie" loaded in application.rb

any ideas how to solve this??

/Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin/application.rb:180:in `rescue in load': uninitialized constant ActiveAdmin::Application::ActiveRecord (NameError)
    from /Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin/application.rb:179:in `load'
    from /Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin/application.rb:171:in `block in load!'
    from /Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin/application.rb:171:in `each'
    from /Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin/application.rb:171:in `load!'
    from /Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin/application.rb:195:in `routes'
    from /Users/fred/.rvm/gems/ruby-2.1.1/bundler/gems/active_admin-8ea922bb6df5/lib/active_admin.rb:80:in `routes'

[johnnyshields]

@fred there was probably a code change done since my original commit. You'll have to raise a new PR and put a if defined?(::ActiveRecord) block around the offending code.

[seanlinsley]

It'd be nice to have a test or two to confirm this doesn't happen in the future, but the test suite is already so slow :-/

[johnnyshields]

Its simple to do--just set hide_const('ActiveRecord') / hide_const('ActiveRecord::Base') and boot the app.

[fred]

Thanks @johnnyshields hope to the pull request in.