Refactor a bit collection input and ensure only label and value methods can be passed

There is no need to keep passing the collection as an arg to the methods,
just use it as an internal method in collection input.

lib/simple_form/inputs/collection_input.rb

@@ -13,10 +13,10 @@ module SimpleForm
       end
 
       def input
-        collection = (options[:collection] || self.class.boolean_collection).to_a
-        detect_collection_methods(collection, options)
-        @builder.send(:"collection_#{input_type}", attribute_name, collection, options[:value_method],
-                      options[:label_method], input_options, input_html_options)
+        label_method, value_method = detect_collection_methods
+
+        @builder.send(:"collection_#{input_type}", attribute_name, collection,
+                      value_method, label_method, input_options, input_html_options)
       end
 
       def input_options
@@ -27,6 +27,10 @@ module SimpleForm
 
     protected
 
+      def collection
+        @collection ||= (options.delete(:collection) || self.class.boolean_collection).to_a
+      end
+
       # Check if :include_blank must be included by default.
       def skip_include_blank?
         (options.keys & [:prompt, :include_blank, :default, :selected]).any? ||
@@ -38,15 +42,20 @@ module SimpleForm
       # on default label and value methods that can be configured through
       # SimpleForm.collection_label_methods and
       # SimpleForm.collection_value_methods.
-      def detect_collection_methods(collection, options)
-        common_method_for = detect_common_display_methods(collection)
+      def detect_collection_methods
+        label, value = options.delete(:label_method), options.delete(:value_method)
 
-        options[:label_method] ||= common_method_for[:label]
-        options[:value_method] ||= common_method_for[:value]
+        unless label && value
+          common_method_for = detect_common_display_methods
+          label ||= common_method_for[:label]
+          value ||= common_method_for[:value]
+        end
+
+        [label, value]
       end
 
-      def detect_common_display_methods(collection)
-        collection_classes = detect_collection_classes(collection)
+      def detect_common_display_methods
+        collection_classes = detect_collection_classes
 
         if collection_classes.include?(Array)
           { :label => :first, :value => :last }
@@ -60,13 +69,13 @@ module SimpleForm
         end
       end
 
-      def detect_collection_classes(collection)
+      def detect_collection_classes
         collection.map { |e| e.class }.uniq
       end
 
       def collection_includes_basic_objects?(collection_classes)
         (collection_classes & [
-         String, Integer, Fixnum, Bignum, Float, NilClass, Symbol, TrueClass, FalseClass
+          String, Integer, Fixnum, Bignum, Float, NilClass, Symbol, TrueClass, FalseClass
         ]).any?
       end
     end

test/inputs_test.rb

@@ -521,6 +521,22 @@ class InputTest < ActionView::TestCase
     assert_select 'label.collection_radio', 'Carlos'
   end
 
+  test 'input should allow overriding only label method for collections' do
+    with_input_for @user, :name, :radio,
+                          :collection => ['Jose' , 'Carlos'],
+                          :label_method => :upcase
+    assert_select 'label.collection_radio', 'JOSE'
+    assert_select 'label.collection_radio', 'CARLOS'
+  end
+
+  test 'input should allow overriding only value method for collections' do
+    with_input_for @user, :name, :radio,
+                          :collection => ['Jose' , 'Carlos'],
+                          :value_method => :upcase
+    assert_select 'input[type=radio][value=JOSE]'
+    assert_select 'input[type=radio][value=CARLOS]'
+  end
+
   test 'input should allow overriding label and value method for collections' do
     with_input_for @user, :name, :radio,
                           :collection => ['Jose' , 'Carlos'],