Minification failed. Returning unminified contents

Question

I have made my first website using MVC 5 which works fine on my local machine but when I publish it to the server some of the CSS is not minifying correctly.

    /* Minification failed. Returning unminified contents.
    (80,1): run-time error CSS1019: Unexpected token, found '@import'
    (80,9): run-time error CSS1019: Unexpected token, found 'url('../Content/dark-skin/skin.css')'
    (671,16): run-time error CSS1062: Expected semicolon or closing curly-brace, found ':'
    (1288,16): run-time error CSS1062: Expected semicolon or closing curly-brace, found ':'
    (1680,1): run-time error CSS1019: Unexpected token, found '@keyframes'
    (1682,5): run-time error CSS1062: Expected semicolon or closing curly-brace, found '50%'
    (1685,1): run-time error CSS1019: Unexpected token, found '@-webkit-keyframes'
    (1687,5): run-time error CSS1062: Expected semicolon or closing curly-brace, found '50%'
     */
    /* NUGET: BEGIN LICENSE TEXT
     *
     * Microsoft grants you the right to use these script files for the sole
     * purpose of either: (i) interacting through your browser with the Microsoft
     * website or online service, subject to the applicable licensing or use
     * terms; or (ii) using the files as included with a Microsoft product subject
     * to that product's license terms. Microsoft reserves all other rights to the
     * files not expressly granted by Microsoft, whether by implication, estoppel
     * or otherwise. The notices and licenses below are for informational purposes only.
     *
     * NUGET: END LICENSE TEXT */
    /*!
     * Bootstrap v3.0.0
     *
     * Copyright 2013 Twitter, Inc
     * Licensed under the Apache License v2.0
     * http://www.apache.org/licenses/LICENSE-2.0
     *
     * Designed and built with all the love in the world by @mdo and @fat.
     *//*! normalize.css v2.1.0 | MIT License | git.io/normalize */

After trying to correct some of the errors and publishing again the error looks the same.

The strangest part is with bootstrap.css which I have slightly modified for the purpose of the website. When I publish it the changes are not in the bundle file. Is it possible that bootstrap is loaded from Bootstrap server and not my project?

    bundles.Add(new StyleBundle("~/Content/cssmain").Include(
                      "~/Content/bootstrap.css",
                      "~/Content/site.css",
                      "~/Content/ilightbox.css",
                      "~/Content/bannerscollection_zoominout.css"));

I have also tried to do minification myself using web application but my changes are not visible and the files do not appear to be minified.

Any help is appreciated.

Answer 1

Make sure the none of those .js files you are bundling end with //Some Comment. If a file ending with a double backslash // comment is tacked on to another dependent file it will be seen as one long comment causing the error you are seeing. I bet there is an //@Import at the end of one of your .js files. If that's the case I think you can probally safely change that line to /*@Import */

Also, I don't know if this was fixed in MVC5 but in MVC4 the minification parser doesn't handle the non-standard :-moz-any() and :-webkit-any() css tags.

Also look at this post that details how to resolve Less @import directories.

Answer 2

We experienced the same issue and it turns out that bootstrap.css is the problem. We were getting the same exact minification errors that you wrote above. The bundler is having problems with @import, @keyframes and @-webkit-keyframes that are in the css file.

What we did to solve the problem is to remove bootstrap.css from the bundle and just reference it directly (or the minified version, if you have it) in the Shared/_Layout.cshtml.

@Styles.Render("~/Content/bootstrap.min.css")
@Styles.Render("~/Content/css")

Answer 3

I resolved the problem bundling bootstrap.css by doing 2 things:

1. Include the bootstrap.css first in the bundle. The code sample in the question already does this, but I was not.
2. Add the official minified version (bootstrap.min.css) to the project in the same directory as the unminified version. This prompts the bundler to use the existing minified file instead of trying (and failing) to minify bootstrap.css itself. See the green arrow in the screenshot below.

Note that if you are using a specific theme, substitute bootstrap.css and bootstrap.min.css with the files provided by the theme. Here's the working code from my project that uses the spacelab theme:

            bundles.Add(new StyleBundle(GetStyleBundlePath("bootstrap")).Include(
            "~/Content/3rdParty/bootstrap.spacelab.css",
            "~/Content/3rdParty/bootstrap-datepicker.css",
            "~/Content/3rdParty/bootstrap-multiselect.css"));

Answer 4

For those that may stumble on this post... You can also resolve this by moving the @import to the first bundled item.

According to: http://webdesign.about.com/cs/css/qt/tipcssatimport.htm

@Import must always be first in the CSS document. When you bundle multipule CSS files together, it chains them into a single bundled css file. Since the second css file added to my bundle, in bundle config, contained an @Import at the start, as the files were chained together the @import appeared towards the middle of the newly merged document. Once I changed the bundle order the issue was resolved.

This is important to understand because although you can use the minified files provided by plugins like bootstrap any changes made to the non-minified files during development will not be added to the existing minified css file. Meaning you will have to make the changes twice, and navigate your way through the minified file.

Answer 5

The issue for me was I had @import in a .css file.

I moved my code into a corresponding .less file that gets compiled on build, which resolved the build error for me. Compiled with Gulp.

Answer 6

Minification Problem Solution:

I know Two types of possible that cause optimization problem :

The invalid CSS files that should be validated before bundling. here is W3C CSS validation service to meet this purpose.

Also considering that Microsoft Optimizer reads content of target resources for minification process, so by using some special phrases like @ sourceMappingURL=jquery.min.map in a JavaScript file or @charset "UTF-8"; in a styleSheet file, the Minification will be failed again. So try to remove or comment them.

Note that by default, Bundling process can't build relative path of image resources in css or js files.

Relative Image Path Solution:

You can use the same path as bundling path like:

bundles.Add(new StyleBundle("~/Content/css/jquery-ui/bundle")
       .Include("~/Content/css/jquery-ui/*.css"));

Where you define the bundle on the same path as the source files that made up the bundle, the relative path of image resources will still work( i.e. /bundle can be any name you like).

Or using new CssRewriteUrlTransform() as second parameter like:

bundles.Add(new StyleBundle("~/Content/css/bundle")
    .Include("~/Content/css/*.css", new CssRewriteUrlTransform()));