MVC 5.1 debug enabled doesn't disable Bundling and minification - visual-studio-2013

Question

Running in debug from VS 2013.2RTM Pro, MVC 5.1 app.
If the compilation mode is set to debug="true" it is supposed to disable Bundling and minification but it does not. When I examine the View source on a page the styles and scripts are bundled.
<script src="/bundles/modernizr?v=K-FFpFNtIXjnmlQamnX3qHX_A5r984M2xbAgcuEm38iv41"></script>
If I set BundleTable.EnableOptimizations = false; in the BundleConfig.cs it does disable Bundling and minification but that is not how it is supposed to work. I shouldn't have to remember to toggle the EnableOptimizations setting!
Things are working properly in VS 2012 MVC 4 apps.
Is this a MVC 5.1 bug? Has anyone else had this problem? Is there a way to get debug to disable the Bundling and minification?
web.config:
<system.web>
<authentication mode="None" />
<compilation debug="true" targetFramework="4.5" />
<httpRuntime targetFramework="4.5" useFullyQualifiedRedirectUrl="true" maxRequestLength="100000" enableVersionHeader="false" />
<sessionState cookieName="My_SessionId" />
<httpModules>
<add name="ErrorLog" type="Elmah.ErrorLogModule, Elmah" />
<add name="ErrorMail" type="Elmah.ErrorMailModule, Elmah" />
<add name="ErrorFilter" type="Elmah.ErrorFilterModule, Elmah" />
</httpModules>
</system.web>
_Layout.cshtml:
In header
#Styles.Render("~/Content/css") #Styles.Render("~/Content/themes/base/css")
#Scripts.Render("~/bundles/modernizr")
At end of body
#Scripts.Render("~/bundles/jquery") #Scripts.Render("~/bundles/jqueryui") #Scripts.Render("~/bundles/jqueryval")

Answer 1

You may have a look at this article
http://codemares.blogspot.com.eg/2012/03/disable-minification-with-mvc-4-bundles.html
or you can use this simple implementation
public class NoMinifyTransform : JsMinify
{
public override void Process(BundleContext context, BundleResponse response)
{
context.EnableOptimizations = false;
var enableInstrumentation = context.EnableInstrumentation;
context.EnableInstrumentation = true;
base.Process(context, response);
context.EnableInstrumentation = enableInstrumentation;
}
}
and then when defining your script bundles in (App_Start) you can use the base Bundle class like this
IBundleTransform jsTransformer;
#if DEBUG
BundleTable.EnableOptimizations = false;
jsTransformer = new NoMinifyTransform();
#else
jstransformer = new JsMinify();
#endif
bundles.Add(new Bundle("~/TestBundle/alljs", jsTransformer)
.Include("~/Scripts/a.js")
.Include("~/Scripts/b.js")
.Include("~/Scripts/c.js"));

Answer 2

I'm seeing this as well in the release version. To get around it, I'm using conditional flags to achieve the same effect.
BundleTable.EnableOptimizations = true;
#if DEBUG
BundleTable.EnableOptimizations = false;
#endif