MVC4 Bundling Cache Headers

This isn't something that we currently expose today. We only expose the Cacheability property on the BundleResponse that a IBundleTransform could change. And yes we explicitly set the following things:

                HttpCachePolicyBase cachePolicy = context.HttpContext.Response.Cache;                cachePolicy.SetCacheability(bundleResponse.Cacheability);                cachePolicy.SetOmitVaryStar(true);                cachePolicy.SetExpires(DateTime.Now.AddYears(1));                cachePolicy.SetValidUntilExpires(true);                cachePolicy.SetLastModified(DateTime.Now);                cachePolicy.VaryByHeaders["User-Agent"] = true;

We have a work item our backlog to open this up and make this more extensible/customizable in the future.

There is a workaround around it as mentioned in janv8000's comment on this response. You need to add the following URL rewrite rule to your web server:

<system.webServer>    <rewrite>        <outboundRules>            <rule name="Cache Bundles" preCondition="IsBundles" patternSyntax="ExactMatch">                <match serverVariable="RESPONSE_Vary" pattern="User-Agent" />                <action type="Rewrite" value="Accept-Encoding" />            </rule>            <preConditions>                <preCondition name="IsBundles" patternSyntax="Wildcard">                    <add input="{URL}" pattern="*/bundles/*" />                </preCondition>            </preConditions>        </outboundRules>    </rewrite></system.webServer>

Obviously you need to pay attention to have all your bundles in your bundles folder or change the IsBundles precondition accordingly.