Fix query with nested array in Active Record

`User.where(id: [[1,2],3])` was equal to `User.where(id:[1, 2, 3])`
in Rails 4.1.x but because of some refactoring in Arel this stopped
working in 4.2.0. This fixes it in Rails.

[Dan Olson & Cristian Bica]

1 files changed, 12 insertions, 4 deletions

diff --git a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
index 78dba8be06..b8d9240bf8 100644
--- a/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
+++ b/activerecord/lib/active_record/relation/predicate_builder/array_handler.rb
@@ -2,12 +2,20 @@ module ActiveRecord
   class PredicateBuilder
     class ArrayHandler # :nodoc:
       def call(attribute, value)
-        return attribute.in([]) if value.empty?
-
         values = value.map { |x| x.is_a?(Base) ? x.id : x }
-        ranges, values = values.partition { |v| v.is_a?(Range) }
         nils, values = values.partition(&:nil?)
 
+        if values.any? { |val| val.is_a?(Array) }
+          ActiveSupport::Deprecation.warn "Passing a nested array to Active Record " \
+            "finder methods is deprecated and will be removed. Flatten your array " \
+            "before using it for 'IN' conditions."
+          values = values.flatten
+        end
+
+        return attribute.in([]) if values.empty? && nils.empty?
+
+        ranges, values = values.partition { |v| v.is_a?(Range) }
+
         values_predicate =
           case values.length
           when 0 then NullPredicate
@@ -20,7 +28,7 @@ module ActiveRecord
         end
 
         array_predicates = ranges.map { |range| attribute.in(range) }
-        array_predicates << values_predicate
+        array_predicates.unshift(values_predicate)
         array_predicates.inject { |composite, predicate| composite.or(predicate) }
       end