Add wrapper mapping per form basis.

Fixes #931.

lib/simple_form.rb

@@ -107,6 +107,8 @@ module SimpleForm
   # Custom wrappers for input types. This should be a hash containing an input
   # type as key and the wrapper that will be used for all inputs with specified type.
   # e.g { string: :string_wrapper, boolean: :boolean_wrapper }
+  # You can also set a wrapper mapping per form basis.
+  # e.g simple_form_for(@foo, wrapper_mapping: { checkbox: :bootstrap_checkbox })
   mattr_accessor :wrapper_mappings
   @@wrapper_mappings = nil
 

lib/simple_form/form_builder.rb

@@ -552,8 +552,16 @@ module SimpleForm
         end
     end
 
+    # Attempts to find a wrapper mapping. It follows the following rules:
+    #
+    # 1) It tries to find a wrapper for the current form
+    # 2) If not, it tries to find a config
     def find_wrapper_mapping(input_type) #:nodoc:
-      SimpleForm.wrapper_mappings && SimpleForm.wrapper_mappings[input_type]
+      if options[:wrapper_mappings] && options[:wrapper_mappings][input_type]
+        options[:wrapper_mappings][input_type]
+      else
+        SimpleForm.wrapper_mappings && SimpleForm.wrapper_mappings[input_type]
+      end
     end
 
     # If cache_discovery is enabled, use the class level cache that persists

test/form_builder/wrapper_test.rb

@@ -200,4 +200,15 @@ class WrapperTest < ActionView::TestCase
       end
     end
   end
+
+  test 'use custom wrapper mapping per form basis' do
+    swap_wrapper :another do
+      with_concat_form_for @user, wrapper_mappings: { string: :another } do |f|
+        concat f.input :name
+      end
+    end
+
+    assert_select "section.custom_wrapper div.another_wrapper label"
+    assert_select "section.custom_wrapper div.another_wrapper input.string"
+  end
 end