Pre-compile emberjs handlebars templates with ASP.NET MVC Bundles

BundleConfig.cs

// use NuGet to add BundleTransformer to your project
// add ember.js and handlebars.js to the /Scripts folder

// in bundle config add something like this
bundles.Add(new ScriptBundle("~/bundles/templates").IncludeDirectory(
  "~/templates", "*.handlebars"));

// or like this
bundles.Add(new ScriptBundle("~/bundles/teamplates").Include(
  "~/templates/application.handlebars",
  "~/templates/header.handlebars",
  "~/templates/footer.handlebars")));

Compiler.cs

public class HandlebarsAssetHandler : AssetHandlerBase {
  public override string ContentType {
    get { return BundleTransformer.Core.Constants.ContentType.Js; }
  }

  /// <summary>Constructs instance of TypeScript asset handler</summary>
  public HandlebarsAssetHandler()
    : this(HttpContext.Current.Cache,
    BundleTransformerContext.Current.GetFileSystemWrapper(),
    BundleTransformerContext.Current.GetCoreConfiguration().AssetHandler,
    BundleTransformerContext.Current.GetApplicationInfo()) { }

  /// <summary>Constructs instance of Handlebars asset handler</summary>
  /// <param name="cache">Server cache</param>
  /// <param name="fileSystemWrapper">File system wrapper</param>
  /// <param name="assetHandlerConfig">Configuration settings of HTTP-handler that responsible 
  /// for text output of processed asset</param>
  /// <param name="applicationInfo">Information about web application</param>
  public HandlebarsAssetHandler(Cache cache, IFileSystemWrapper fileSystemWrapper,
    AssetHandlerSettings assetHandlerConfig, IHttpApplicationInfo applicationInfo)
    : base(cache, fileSystemWrapper, assetHandlerConfig, applicationInfo) { }

  /// <summary>Translates handlebars templates to JS-code</summary>
  /// <param name="asset">Handlebars template</param>
  /// <returns>Asset with translated code</returns>
  protected override IAsset ProcessAsset(IAsset asset) {
    ITranslator handlebarsTranslator = BundleTransformerContext.Current.GetJsTranslatorInstance("HandlebarsTranslator");
    handlebarsTranslator.IsDebugMode = _applicationInfo.IsDebugMode;
    return handlebarsTranslator.Translate(asset);
  }
}

public class HandlebarsTranslator : TranslatorWithNativeMinificationBase {
  private readonly MsieJsEngine jsEngine = new MsieJsEngine();

  public HandlebarsTranslator() {
    //setup a dummy browser environment with jquery
    jsEngine.Execute(@"
      var window = this
      //dummy jQuery
      var $ = jQuery = function () { return jQuery }
      jQuery.ready = function () { return jQuery }
      jQuery.inArray = function () { return jQuery }
      jQuery.jquery = '1.8.2'
      jQuery.event = { fixHooks: {} }

      //dummy DOM element
      var element = {
        firstChild: function () { return element },
        innerHTML: function () { return element }
      }

      // DOM
      var document = {
        createRange: false,
        createElement: function () { return element }
      }

      // Console
      var console = {
        log: function () {}
      }
    ");
    //load handlebars and ember
    var server = new AspServerPathResolver();
    jsEngine.ExecuteFile(server.GetFullPath("~/Scripts/handlebars.js"));
    jsEngine.ExecuteFile(server.GetFullPath("~/Scripts/ember.js"));
  }

  public override IAsset Translate(IAsset asset) {
    // inject the template
    jsEngine.SetVariableValue("template", asset.Content);
    // compile
    string templateJs = jsEngine.Evaluate<string>("Ember.Handlebars.precompile(template).toString()");
    // add the template to the collection
    var templateName = Path.GetFileNameWithoutExtension(asset.Path);
    asset.Content = "Ember.TEMPLATES['" + templateName + "'] = Ember.Handlebars.template(" + templateJs + ");";
    return asset;
  }

  public override IList<IAsset> Translate(IList<IAsset> assets) {
    foreach (IAsset asset in assets) {
      Translate(asset);
    }
    return assets;
  }
}

Web.config.xml

<!-- Add relevant bits to your web config and fix namespaces/assembly names -->

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <system.web>
    <httpHandlers>
      <add path="*.handlebars" verb="GET" type="yournamespace.HandlebarsAssetHandler, yourassembly" />
    </httpHandlers>
  </system.web>
  <system.webServer>
    <handlers>
      <add name="HandlebarsAssetHandler" path="*.handlebars" verb="GET" type="yournamespace.HandlebarsAssetHandler, yourassembly" resourceType="File" preCondition="" />
    </handlers>
  </system.webServer>
  <bundleTransformer xmlns="http://tempuri.org/BundleTransformer.Configuration.xsd">
    <core>
      <js>
        <translators>
          <add name="HandlebarsTranslator" type="yournamespace.HandlebarsTranslator, yourassembly" enabled="true" />
        </translators>
      </js>
    </core>
  </bundleTransformer>
</configuration>

This example turns out to be buggy for production use, but can be used as a starting point.