don't cache the identity menu when masquerading

we would need a separate cache for each [@current_user,
@real_current_user] combination because the authenticity token is
included in the html here -- it's not really worth it, just skip the
cache when masquerading.

Change-Id: Ie1440a6e592ef96649467e06006520d176438a70
Reviewed-on: https://gerrit.instructure.com/6385
Tested-by: Hudson <hudson@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>

app/helpers/application_helper.rb

@@ -558,4 +558,12 @@ var I18n = I18n || {};
     ].any?{ |e| e.respond_to?(:count) && e.count > 0 }
   end
 
+  def cache_if(cond, *args)
+    if cond
+      cache(*args) { yield }
+    else
+      yield
+    end
+  end
+
 end

app/views/layouts/application.html.erb

@@ -75,7 +75,7 @@
       <% if (identity = yield :identity) %>
         <%= identity %>
       <% else %>
-        <%- cache([@current_user || 'nobody', (@real_current_user && @real_current_user != @current_user ? 'm' : 'a'), 'identity-15m'], :expires_in => 15.minutes) do -%>
+        <%- cache_if(!@real_current_user, [@current_user || 'nobody', 'identity-15m'], :expires_in => 15.minutes) do -%>
           <%= render(:partial => 'shared/identity') %>
         <%- end -%>
       <% end %>

spec/helpers/application_helper_spec.rb

@@ -107,4 +107,20 @@ describe ApplicationHelper do
       tomorrow_at_midnight.should > now
     end
   end
+
+  describe "cache_if" do
+    it "should cache the fragment if the condition is true" do
+      enable_cache do
+        cache_if(true, "t1", :expires_in => 15.minutes, :no_locale => true) { output_buffer.concat "blargh" }
+        @controller.read_fragment("t1").should == "blargh"
+      end
+    end
+
+    it "should not cache if the condition is false" do
+      enable_cache do
+        cache_if(false, "t1", :expires_in => 15.minutes, :no_locale => true) { output_buffer.concat "blargh" }
+        @controller.read_fragment("t1").should be_nil
+      end
+    end
+  end
 end

spec/spec_helper.rb

@@ -386,10 +386,16 @@ Spec::Runner.configure do |config|
 
   def enable_cache
     old_cache = RAILS_CACHE
-    silence_warnings { Object.const_set(:RAILS_CACHE, ActiveSupport::Cache::MemoryStore.new) }
+    new_cache = ActiveSupport::Cache::MemoryStore.new
+    ActionController::Base.cache_store = new_cache
+    silence_warnings { Object.const_set(:RAILS_CACHE, new_cache) }
+    old_perform_caching = ActionController::Base.perform_caching
+    ActionController::Base.perform_caching = true
     yield
   ensure
     silence_warnings { Object.const_set(:RAILS_CACHE, old_cache) }
+    ActionController::Base.cache_store = old_cache
+    ActionController::Base.perform_caching = old_perform_caching
   end
 
   # enforce forgery protection, so we can verify usage of the authenticity token