Ensure we always use foreign key name on association.

lib/simple_form/form_builder.rb

@@ -95,10 +95,12 @@ module SimpleForm
     def association(attribute, options={})
       raise ArgumentError, "Association cannot be used in forms not associated with an object" unless @object
 
-      options[:collection] ||= begin
-        association = find_association(attribute)
-        raise "Association not found #{attribute.inspect}" unless association
+      association = find_association(attribute)
+      raise "Association not found #{attribute.inspect}" unless association
 
+      attribute = association.options[:foreign_key] || :"#{association.name}_id"
+
+      options[:collection] ||= begin
         find_options = { :conditions => options.delete(:conditions),
                          :order => options.delete(:order) }
         association.klass.all(find_options)

test/form_builder_test.rb

@@ -346,7 +346,7 @@ class FormBuilderTest < ActionView::TestCase
 
   test 'builder should allow creating an association input generating collection' do
     with_association_for @user, :company
-    assert_select 'form select.select#user_company'
+    assert_select 'form select.select#user_company_id'
     assert_select 'form select option[value=1]', 'Company 1'
     assert_select 'form select option[value=2]', 'Company 2'
     assert_select 'form select option[value=3]', 'Company 3'
@@ -354,7 +354,7 @@ class FormBuilderTest < ActionView::TestCase
 
   test 'builder should allow passing conditions to find collection' do
     with_association_for @user, :company, :conditions => { :id => 1 }
-    assert_select 'form select.select#user_company'
+    assert_select 'form select.select#user_company_id'
     assert_select 'form select option[value=1]'
     assert_no_select 'form select option[value=2]'
     assert_no_select 'form select option[value=3]'
@@ -362,7 +362,7 @@ class FormBuilderTest < ActionView::TestCase
 
   test 'builder should allow passing order to find collection' do
     with_association_for @user, :company, :order => 'name'
-    assert_select 'form select.select#user_company'
+    assert_select 'form select.select#user_company_id'
     assert_no_select 'form select option[value=1]'
     assert_no_select 'form select option[value=2]'
     assert_select 'form select option[value=3]'
@@ -372,7 +372,7 @@ class FormBuilderTest < ActionView::TestCase
     with_association_for @user, :company,
                          :collection => [Company.new(999, 'Teste')],
                          :options => { :include_blank => false }
-    assert_select 'form select.select#user_company'
+    assert_select 'form select.select#user_company_id'
     assert_no_select 'form select option[value=1]'
     assert_select 'form select option[value=999]', 'Teste'
     assert_select 'form select option', :count => 1

test/support/models.rb

@@ -1,7 +1,7 @@
 require 'ostruct'
 
 Column = Struct.new(:name, :type, :limit)
-Association = Struct.new(:klass)
+Association = Struct.new(:klass, :name, :options)
 
 class Company < Struct.new(:id, :name)
   def self.all(options={})
@@ -56,7 +56,7 @@ class User < OpenStruct
   end
 
   def self.reflect_on_association(association)
-    Association.new(Company) if association == :company
+    Association.new(Company, association, {}) if association == :company
   end
 
   def errors