Only flatten 1 level in push and add to set:

[ fix #3093 ]

CHANGELOG.md

@@ -226,6 +226,8 @@ For instructions on upgrading to newer versions, visit
 
 * \#3116 Relations instance variables are now all prefixed with `_`.
 
+* \#3093 Only flatten 1 level when atomically pushing arrays.
+
 * \#3063 `Document#becomes` now properly sets base object on errors.
   (Adam Ross Cohen)
 

lib/mongoid/persistable/pushable.rb

@@ -23,7 +23,7 @@ def add_to_set(adds)
         prepare_atomic_operation do |ops|
           process_atomic_operations(adds) do |field, value|
             existing = send(field) || (attributes[field] ||= [])
-            values = [ value ].flatten
+            values = [ value ].flatten(1)
             values.each do |val|
               existing.push(val) unless existing.include?(val)
             end
@@ -50,7 +50,7 @@ def push(pushes)
         prepare_atomic_operation do |ops|
           process_atomic_operations(pushes) do |field, value|
             existing = send(field) || (attributes[field] ||= [])
-            values = [ value ].flatten
+            values = [ value ].flatten(1)
             values.each{ |val| existing.push(val) }
             ops[atomic_attribute_name(field)] = { "$each" => values }
           end

spec/app/models/person.rb

@@ -34,6 +34,7 @@ class Person
   field :desc, localize: true
   field :test_array, type: Array
   field :overridden_setter, type: String
+  field :arrays, type: Array
 
   index age: 1
   index addresses: 1

spec/mongoid/persistable/pushable_spec.rb

@@ -35,6 +35,10 @@
         it "persists absent values" do
           expect(person.reload.test_array).to eq([ 1 ])
         end
+
+        it "flattens only 1 level" do
+          expect(person.reload.arrays).to eq([[ 7, 8 ]])
+        end
       end
 
       let(:person) do
@@ -44,7 +48,7 @@
       context "when provided string fields" do
 
         let!(:add) do
-          person.add_to_set("aliases" => 4, "array" => [4, 5], "test_array" => 1)
+          person.add_to_set("aliases" => 4, "array" => [4, 5], "test_array" => 1, "arrays" => [[ 7, 8 ]])
         end
 
         it_behaves_like "a unique pushable root document"
@@ -53,7 +57,7 @@
       context "when provided symbol fields" do
 
         let!(:add) do
-          person.add_to_set(aliases: 4, array: [4, 5], test_array: 1)
+          person.add_to_set(aliases: 4, array: [4, 5], test_array: 1, arrays: [[ 7, 8 ]])
         end
 
         it_behaves_like "a unique pushable root document"
@@ -158,6 +162,10 @@
         it "persists absent values" do
           expect(person.reload.test_array).to eq([ 1 ])
         end
+
+        it "flattens only 1 level" do
+          expect(person.reload.arrays).to eq([[ 7, 8 ]])
+        end
       end
 
       let(:person) do
@@ -167,7 +175,7 @@
       context "when provided string fields" do
 
         let!(:push) do
-          person.push("aliases" => 4, "array" => [ 7, 8 ], "test_array" => 1)
+          person.push("aliases" => 4, "array" => [ 7, 8 ], "test_array" => 1, "arrays" => [[ 7, 8 ]])
         end
 
         it_behaves_like "a pushable root document"
@@ -176,7 +184,7 @@
       context "when provided symbol fields" do
 
         let!(:push) do
-          person.push(aliases: 4, array: [ 7, 8 ], test_array: 1)
+          person.push(aliases: 4, array: [ 7, 8 ], test_array: 1, arrays: [[ 7, 8 ]])
         end
 
         it_behaves_like "a pushable root document"