Following the false issue reporting I did here : https://github.com/rails/rails/issues/6958

- Enable propagation of :skip_types, :dasherize and :camelize on included models by default
- Adding the option to override this propagation on a per-include basis (:include => { :model => { :dasherize => false } }
- Enough tests to prove it works
- Updated activemodel CHANGELOG.md

Squashed my commits

3 files changed, 43 insertions, 1 deletions

diff --git a/activemodel/CHANGELOG.md b/activemodel/CHANGELOG.md
index 9188719b78..12e0956d3c 100644
--- a/activemodel/CHANGELOG.md
+++ b/activemodel/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## Rails 4.0.0 (unreleased) ##
 
+*   Changed `ActiveModel::Serializers::Xml::Serializer#add_associations` to by default propagate `:skip_types, :dasherize, :camelize` keys to included associations. It can be overriden on each association by explicitly specifying the option on one or more associations *Anthony Alberto*
+
 *   Changed `AM::Serializers::JSON.include_root_in_json' default value to false.
     Now, AM Serializers and AR objects have the same default behaviour. Fixes #6578.
 
diff --git a/activemodel/lib/active_model/serializers/xml.rb b/activemodel/lib/active_model/serializers/xml.rb
index 016d821fdf..cf742d0569 100644..100755
--- a/activemodel/lib/active_model/serializers/xml.rb
+++ b/activemodel/lib/active_model/serializers/xml.rb
@@ -115,6 +115,10 @@ module ActiveModel
           merged_options = opts.merge(options.slice(:builder, :indent))
           merged_options[:skip_instruct] = true
 
+          [:skip_types, :dasherize, :camelize].each do |key|
+            merged_options[key] = options[key] if merged_options[key].nil? && !options[key].nil?
+          end
+
           if records.respond_to?(:to_ary)
             records = records.to_ary
 
diff --git a/activemodel/test/cases/serializers/xml_serialization_test.rb b/activemodel/test/cases/serializers/xml_serialization_test.rb
index a93323a3a8..8c5a3c5efd 100644..100755
--- a/activemodel/test/cases/serializers/xml_serialization_test.rb
+++ b/activemodel/test/cases/serializers/xml_serialization_test.rb
@@ -28,7 +28,7 @@ class Address
   extend ActiveModel::Naming
   include ActiveModel::Serializers::Xml
 
-  attr_accessor :street, :city, :state, :zip
+  attr_accessor :street, :city, :state, :zip, :apt_number
 
   def attributes
     instance_values
@@ -56,6 +56,7 @@ class XmlSerializationTest < ActiveModel::TestCase
     @contact.address.city = "Springfield"
     @contact.address.state = "CA"
     @contact.address.zip = 11111
+    @contact.address.apt_number = 35
     @contact.friends = [Contact.new, Contact.new]
   end
 
@@ -222,4 +223,39 @@ class XmlSerializationTest < ActiveModel::TestCase
     assert_match %r{<friends>}, xml
     assert_match %r{<friend>}, xml
   end
+
+  test "propagates skip-types option to included associations and attributes" do
+    xml = @contact.to_xml :skip_types => true, :include => :address, :indent => 0
+    assert_match %r{<address>}, xml
+    assert_match %r{<apt-number>}, xml
+  end
+
+  test "propagates camelize option to included associations and attributes" do
+    xml = @contact.to_xml :camelize => true, :include => :address, :indent => 0
+    assert_match %r{<Address>}, xml
+    assert_match %r{<AptNumber type="integer">}, xml
+  end
+
+  test "propagates dasherize option to included associations and attributes" do
+    xml = @contact.to_xml :dasherize => false, :include => :address, :indent => 0
+    assert_match %r{<apt_number type="integer">}, xml
+  end
+
+  test "don't propagate skip_types if skip_types is defined at the included association level" do
+    xml = @contact.to_xml :skip_types => true, :include => { :address => { :skip_types => false } }, :indent => 0
+    assert_match %r{<address>}, xml
+    assert_match %r{<apt-number type="integer">}, xml
+  end
+
+  test "don't propagate camelize if camelize is defined at the included association level" do
+    xml = @contact.to_xml :camelize => true, :include => { :address => { :camelize => false } }, :indent => 0
+    assert_match %r{<address>}, xml
+    assert_match %r{<apt-number type="integer">}, xml
+  end
+
+  test "don't propagate dasherize if dasherize is defined at the included association level" do
+    xml = @contact.to_xml :dasherize => false, :include => { :address => { :dasherize => true } }, :indent => 0
+    assert_match %r{<address>}, xml
+    assert_match %r{<apt-number type="integer">}, xml
+  end
 end