Always expand */*

actionpack/lib/action_view/lookup_context.rb

@@ -167,15 +167,12 @@ module ActionView
         @frozen_formats = true
       end
 
-      # Overload formats= to reject ["*/*"] values.
+      # Overload formats= to expand ["*/*"] values and automatically
+      # add :html as fallback to :js.
       def formats=(values)
         if values
-          values.pop if values.last == "*/*"
-          if values.size == 0
-            values = nil
-          elsif values == [:js]
-            values << :html
-          end
+          values.concat(_formats_defaults) if values.delete "*/*"
+          values << :html if values == [:js]
         end
         super(values)
       end

actionpack/test/template/lookup_context_test.rb

@@ -53,7 +53,7 @@ class LookupContextTest < ActiveSupport::TestCase
 
   test "handles explicitly defined */* formats fallback to :js" do
     @lookup_context.formats = [:js, Mime::ALL]
-    assert_equal [:js, :html], @lookup_context.formats
+    assert_equal [:js, *Mime::SET.symbols], @lookup_context.formats
   end
 
   test "adds :html fallback to :js formats" do