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]

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 @@ def call(attribute, value)
         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
 

activerecord/test/cases/finder_test.rb

@@ -521,6 +521,34 @@ def test_find_on_hash_conditions_with_array_of_integers_and_ranges
     assert_equal [1,2,3,5,6,7,8,9], Comment.where(id: [1..2, 3, 5, 6..8, 9]).to_a.map(&:id).sort
   end
 
+  def test_find_on_hash_conditions_with_array_of_ranges
+    assert_equal [1,2,6,7,8], Comment.where(id: [1..2, 6..8]).to_a.map(&:id).sort
+  end
+
+  def test_find_on_hash_conditions_with_nested_array_of_integers_and_ranges
+    assert_deprecated do
+      assert_equal [1,2,3,5,6,7,8,9], Comment.where(id: [[1..2], 3, [5], 6..8, 9]).to_a.map(&:id).sort
+    end
+  end
+
+  def test_find_on_hash_conditions_with_array_of_integers_and_arrays
+    assert_deprecated do
+      assert_equal [1,2,3,5,6,7,8,9], Comment.where(id: [[1, 2], 3, 5, [6, [7], 8], 9]).to_a.map(&:id).sort
+    end
+  end
+
+  def test_find_on_hash_conditions_with_nested_array_of_integers_and_ranges_and_nils
+    assert_deprecated do
+      assert_equal [1,3,4,5], Topic.where(parent_id: [[2..6], nil]).to_a.map(&:id).sort
+    end
+  end
+
+  def test_find_on_hash_conditions_with_nested_array_of_integers_and_ranges_and_more_nils
+    assert_deprecated do
+      assert_equal [], Topic.where(parent_id: [[7..10, nil, [nil]], [nil]]).to_a.map(&:id).sort
+    end
+  end
+
   def test_find_on_multiple_hash_conditions
     assert Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: false).find(1)
     assert_raise(ActiveRecord::RecordNotFound) { Topic.where(author_name: "David", title: "The First Topic", replies_count: 1, approved: true).find(1) }

activerecord/test/cases/relation/where_test.rb

@@ -181,7 +181,9 @@ def test_where_with_table_name_and_empty_array
     end
 
     def test_where_with_table_name_and_nested_empty_array
-      assert_equal [], Post.where(:id => [[]]).to_a
+      assert_deprecated do
+        assert_equal [], Post.where(:id => [[]]).to_a
+      end
     end
 
     def test_where_with_empty_hash_and_no_foreign_key

activerecord/test/fixtures/developers.yml

@@ -18,4 +18,4 @@ dev_<%= digit %>:
 poor_jamis:
   id: 11
   name: Jamis
-  salary: 9000
\ No newline at end of file
+  salary: 9000