BundleTransformer.Less unable to parse variables in @import statements

Question

EDIT: So according to this it is not possible which is a real shame. I will need to look for a library that bundles and compresses with the support of variables in imports.

I am having trouble trying to get BundleTransformer.Less to parse the following LESS:

// There is a path to Startup framework
@startup-basePath: "../../../";

@import '@{startup-basePath}flat-ui/less/config.less';
@import '@{startup-basePath}flat-ui/less/mixins.less';

And it is producing the following error:

You are importing a file ending in .less that cannot be found.":"/lib/startup/samples/template/less/@{startup-basePath}flat-ui/less/config.less

The files does exist but as you can see it isn't parsing the variable in the location string. Web Essentials in VS2013 has no problem compiling the LESS files and output the CSS as expected. I suspect the issue lies with BundleTransformer or the way that have set it up. I am using the following version:

Id                             Version              Description/Release Notes                                                                                                                                      
--                             -------              -------------------------                                                                                                                                      
BundleTransformer.Core         1.8.0                Bundle Transformer - a modular extension for System.Web.Optimization (aka Microsoft ASP.NET Web Optimization Framework). Classes `CssTransformer` and `JsTra...
BundleTransformer.Less         1.7.16               BundleTransformer.Less contains translator-adapter LessTranslator. This adapter makes translation of LESS-code to CSS-code. Also contains HTTP-handler LessA...
BundleTransformer.Yui          1.8.0                BundleTransformer.Yui contains 2 minifier-adapters: `YuiCssMinifier` (for minification of CSS-code) and `YuiJsMinifier` (for minification of JS-code). These...

I have to use these versions as I am using Umbraco 7 and it will not allow me to update Newtonsoft.Json without breaking Umbraco.

My bundle config file looks like the following:

public static void RegisterBundles(BundleCollection bundles)
{
    bundles.UseCdn = true;

    var nullBuilder = new NullBuilder();
    var nullOrderer = new NullOrderer();

    // CSS + LESS
    var libCSS = new CustomStyleBundle("~/libCSS");
    libCSS.Include(
        "~/Content/font-awesome.css",

        // LESS
        "~/lib/startup/samples/template/less/style.less");

    libCSS.Orderer = nullOrderer;

    bundles.Add(libCSS);
}

I assumed that the issue was with the Less transformer not being registered correctly but I have followed the installation instructions to the letter, please see the documentation for the LESS version. Can anybody see something that I am missing that would help solve this issue or could anyone recommend something that I could try?

All help appreciated.

Answer 1

I have also tried this library, but unsuccessfully :/

Best solution for compiling LESS are node.js packages LESS (https://www.npmjs.org/package/less) or Recess (http://twitter.github.io/recess/).

Because your LESS files won't be changed after you deploy web project, you don't have to generate css during each application initialization.

You can also generate CSS before application builds or after saving LESS file.

If you're interested i can help you with more informations.

Answer 2

I have had better luck with the 1.9.40 and 1.9.34 versions of these BundleTransformer packages. I had problems with the 1.8 versions failing at times. We've been using BundleTransformer.Core.1.9.40, BundleTransformer.Less.1.9.40, and BundleTransformer.Yui.1.9.34 for a couple of weeks now without any of the errors of the 1.8 versions.

Answer 3

BundleTransformer.Less does not support the string interpolation in file paths (see «Is string interpolation not supported?» discussion).

UPDATE: In BundleTransformer.Less version 1.9.92 now supports the interpolation in file paths.