Allow registering javascript/stylesheet_expansions to existing symbols

actionpack/lib/action_view/helpers/asset_tag_helpers/javascript_tag_helpers.rb

@@ -59,7 +59,10 @@ module ClassMethods
           #     <script type="text/javascript" src="/javascripts/body.js"></script>
           #     <script type="text/javascript" src="/javascripts/tail.js"></script>
           def register_javascript_expansion(expansions)
-            JavascriptIncludeTag.expansions.merge!(expansions)
+            js_expansions = JavascriptIncludeTag.expansions
+            expansions.each do |key, values|
+              js_expansions[key] = (js_expansions[key] || []) | Array(values) if values
+            end
           end
         end
 
@@ -170,4 +173,4 @@ def javascript_include_tag(*sources)
 
     end
   end
-end
\ No newline at end of file
+end

actionpack/lib/action_view/helpers/asset_tag_helpers/stylesheet_tag_helpers.rb

@@ -44,7 +44,10 @@ module ClassMethods
           #     <link href="/stylesheets/body.css"  media="screen" rel="stylesheet" type="text/css" />
           #     <link href="/stylesheets/tail.css"  media="screen" rel="stylesheet" type="text/css" />
           def register_stylesheet_expansion(expansions)
-            StylesheetIncludeTag.expansions.merge!(expansions)
+            style_expansions = StylesheetIncludeTag.expansions
+            expansions.each do |key, values|
+              style_expansions[key] = (style_expansions[key] || []) | Array(values) if values
+            end
           end
         end
 
@@ -141,4 +144,4 @@ def stylesheet_link_tag(*sources)
 
     end
   end
-end
\ No newline at end of file
+end

actionpack/test/template/asset_tag_helper_test.rb

@@ -54,6 +54,9 @@ def url_for(*args)
   def teardown
     config.perform_caching = false
     ENV.delete('RAILS_ASSET_ID')
+
+    JavascriptIncludeTag.expansions.clear
+    StylesheetIncludeTag.expansions.clear
   end
 
   AutoDiscoveryToTag = {
@@ -268,6 +271,14 @@ def test_custom_javascript_expansions_and_defaults_puts_application_js_at_the_en
     assert_dom_equal  %(<script src="/javascripts/controls.js" type="text/javascript"></script>\n<script src="/javascripts/prototype.js" type="text/javascript"></script>\n<script src="/javascripts/effects.js" type="text/javascript"></script>\n<script src="/javascripts/dragdrop.js" type="text/javascript"></script>\n<script src="/javascripts/controls.js" type="text/javascript"></script>\n<script src="/javascripts/rails.js" type="text/javascript"></script>\n<script src="/javascripts/bank.js" type="text/javascript"></script>\n<script src="/javascripts/robber.js" type="text/javascript"></script>\n<script src="/javascripts/effects.js" type="text/javascript"></script>\n<script src="/javascripts/application.js" type="text/javascript"></script>), javascript_include_tag('controls',:defaults, :robbery, 'effects')
   end
 
+  def test_registering_javascript_expansions_merges_with_existing_expansions
+    ENV["RAILS_ASSET_ID"] = ""
+    ActionView::Helpers::AssetTagHelper::register_javascript_expansion :can_merge => ['bank']
+    ActionView::Helpers::AssetTagHelper::register_javascript_expansion :can_merge => ['robber']
+    ActionView::Helpers::AssetTagHelper::register_javascript_expansion :can_merge => ['bank']
+    assert_dom_equal  %(<script src="/javascripts/bank.js" type="text/javascript"></script>\n<script src="/javascripts/robber.js" type="text/javascript"></script>), javascript_include_tag(:can_merge)
+  end
+
   def test_custom_javascript_expansions_with_undefined_symbol
     ActionView::Helpers::AssetTagHelper::register_javascript_expansion :monkey => nil
     assert_raise(ArgumentError) { javascript_include_tag('first', :monkey, 'last') }
@@ -327,6 +338,14 @@ def test_custom_stylesheet_expansions_with_undefined_symbol
     assert_raise(ArgumentError) { stylesheet_link_tag('first', :monkey, 'last') }
   end
 
+  def test_registering_stylesheet_expansions_merges_with_existing_expansions
+    ENV["RAILS_ASSET_ID"] = ""
+    ActionView::Helpers::AssetTagHelper::register_stylesheet_expansion :can_merge => ['bank']
+    ActionView::Helpers::AssetTagHelper::register_stylesheet_expansion :can_merge => ['robber']
+    ActionView::Helpers::AssetTagHelper::register_stylesheet_expansion :can_merge => ['bank']
+    assert_dom_equal  %(<link href="/stylesheets/bank.css" media="screen" rel="stylesheet" type="text/css" />\n<link href="/stylesheets/robber.css" media="screen" rel="stylesheet" type="text/css" />), stylesheet_link_tag(:can_merge)
+  end
+
   def test_image_path
     ImagePathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end