ValidatesUniqueness mismatches the implementation of unique indexes in dm-constraints

[tillsc]

Given a model

class Foo
  property :num1, Integer, :unique => :scope_name
  property :num2, Integer, :unique => :scope_name
  belongs_to :bar, :unique => :scope_name
end

This example results into a perfectly working unique index "unique_foos_scope_name" with three fields ('num1', 'num2' and 'bar_id'). But the validation won't work and would throw the following exception:

dm-validations/lib/dm-validations/validators/uniqueness_validator.rb

Line 39 in c874faf

raise(ArgumentError,"Could not find property to scope by: #{subject}. Note that :unique does not currently support arbitrarily named groups, for that you should use :unique_index with an explicit validates_uniqueness_of.")

Following the instructions from the exception this would lead to the following model:

class Foo
  property :num1, Integer
  property :num2, Integer, :unique => [:num1, :bar]
  belongs_to :bar
end

Now the Validation is working but the generated indexes are crap (unique index with only one field: 'num2').

The only solution to fix this would be to address the constraints separately:

class Foo
  property :num1, Integer, :unique_index => :index_name
  property :num2, Integer, :unique => [:num1, :bar], :unique_index => :index_name
  belongs_to :bar, :unique_index => :index_name
end

But this also breaks the application because belongs_to can't handle the :unique_index option correctly. So you'll have to use:

class Foo
  property :num1, Integer, :unique_index => :index_name
  property :num2, Integer, :unique => [:num1, :bar], :unique_index => :index_name
  belongs_to :bar
  property :bar_id, :unique_index => :index_name, :index => true
end

This seems to work but I don't think this is what the most people want :-)

[tillsc]

BTW: See also http://irclogger.com/.datamapper/2011-08-26#1314369913