usemin and rewriting urls of images in vendor CSS

Question

grunt-usemin helps me to transform

<link href="/dependencies/bootstrap/dist/css/bootstrap.min.css" rel="stylesheet" />
<link href="/dependencies/nanoscroller/bin/css/nanoscroller.css" rel="stylesheet" />
<link href="/dependencies/dropzone/downloads/css/dropzone.css" rel="stylesheet" />

to a perfectly combined and minified js:

<link href="scripts/8e1991c7.libraries.js" rel="stylesheet" />

After concat, cssmin and uglify I have a almost perfect folder structure except for images and their locations.

Here is my problem:

All these vendor's css files are including image locations. The bad thing is that all of them are sharing different kind of locations. Some of them are using images inside css folder whereas others are using inside img folder.

How can I configure grunt usemin to rewrite all images urls?

Answer 1

What fixed the CSS background-image revving for me was to add a CSS pattern in options, which finds all asset references in the CSS and replaces them with the revved assets.

// Performs rewrites based on rev and the useminPrepare configuration
usemin: {
  ...
  ...
  options: {
    ...
    ...
    // This is so we update image references in our ng-templates
    patterns: {
      js: [
        [/(assets\/images\/.*?\.(?:gif|jpeg|jpg|png|webp|svg))/gm, 'Update the JS to reference our revved images']
      ],
      css: [
        [/(assets\/images\/.*?\.(?:gif|jpeg|jpg|png|webp|svg))/gm, 'Update the CSS to reference our revved images']
      ]
    }
  }
},

Answer 2

1) Rev images. Add paths of images into rev task.

rev: {
    dist: {
        files: {
            src: [
                '<%= yeoman.dist %>/static/scripts/{,*/}*.js',
                '<%= yeoman.dist %>/static/styles/{,*/}*.css',
                '<%= yeoman.dist %>/static/images/{,*/}*.{png,jpg,jpeg,gif,webp,svg}',
            ]
        }
    }
}

2) Add paths of file which are including image locations into usemin task.

usemin: {
    html: ['<%= yeoman.dist %>/{,*/}*.html'],
    css: ['<%= yeoman.dist %>/static/styles/{,*/}*.css'],
    options: {
        assetsDirs: ['<%= yeoman.dist %>','<%= yeoman.dist%>/static/images'],
    }
}

3) Run grunt.

Answer 3

My approach to this problem was to basically create a separate styles/select2/select2.css for each vendor style, and then all relevant images can be copied by Grunt into styles/select2 (without having to worry about relative paths or overwriting etc) as part of the script. That is:

app/index.html

<!-- build:css(.tmp) styles/select2/select2.css -->
<link rel="stylesheet" href="bower_components/select2/select2.css">
<!-- endbuild -->

Gruntfile.js

Add a new copy task that will copy over vendor styles into the .tmp directory before they are minimised with cssmin:

    copy: {
        // this copies bower_components/*.css into .tmp so they can be compiled
        styles: {
            expand: true,
            cwd: '<%= yeoman.app %>',
            dest: '.tmp/',
            src: [
                'styles/{,*/}*.css',
                'bower_components/**/*.css'
            ]
        },
        dist: ...

And then once they are minimised, copy over the relevant assets (which in this case I'm assuming is just PNG and GIF images):

        // and once we have compiled all of our stylesheets, we need to also copy over any necessary image files
        distAssets: {
            expand: true,
            cwd: '<%= yeoman.app %>/bower_components',
            dest: '<%= yeoman.dist %>/styles',
            src: [
                '**/*.png',
                '**/*.gif'
            ]
        }
    },

Finally, add the new tasks into the build task:

grunt.registerTask('build', [
    'clean:dist',
    'replace:dist',
    'copy:styles',  // -- added
    'useminPrepare',
    // ... etc ...
    'copy',
    'rev',
    'usemin',
    'copy:distAssets'  // -- added
]);

Answer 4

I've solved the problem using the following.

useminPrepare: {
    html: 'src/index.html',
    options: {
        dest: 'build',
        flow: {
            html: {
                steps: {
                    js: ['concat', 'uglifyjs'],
                    css: ['cssmin']
                },
                post: {}
            }
        }
    }
},
cssmin: {
    options: {
        root: 'src'
    }
}

First, we are overriding useminPrepare's flow, removing the concat task from the css flows. This is needed because concat will destroy relative path information. Since cssmin will itself concat multiple files together, the sepearte concat task is only harmful. (https://github.com/yeoman/grunt-usemin/issues/225)

Lastly, we are telling cssmin where the "root" of your project is from the Gruntfile. This helps cssmin rewrite the relative urls it finds relative to this "root" directory.

Answer 5

I did a little digging around and found a pair of tasks that look like they'll get the job done: https://github.com/yeoman/grunt-filerev & https://github.com/richardbolt/grunt-cssurlrev. The only problem with this is that you'll have to configure the paths inside your Gruntfile manually, like so:

grunt.initConfig({
    filerev: {
      images: {
        src: ['img1.png', 'img2.png'],
        dest: 'tmp'
      }
    },
    cssurlrev: {
      dist: {
        src: ['public/css/*.css']
      },
    }
});

To my knowledge there isn't a plugin that does this task automatically.

Answer 6

I had to implement a new task. This is my preliminary implementation.

grunt.registerMultiTask('rewriteCssUrl', 'rewrite url in css', function () {
  var options = this.options({
     assets: grunt.filerev ? grunt.filerev.summary : {},
     postFilter: function identity(input){ return input}
  });

  var self = this;
  var assets = options.assets;

  self.filesSrc.forEach(function (file) {
     var css = grunt.file.read(file);
     var original = css;

     css = css.replace(/(?:src=|url\(\s*)['"]?([^'"\)]+)['"]?\s*\)?/gm, function (match, src) {
        var key = path.join(path.dirname(file), src);
        var asset = assets[path.normalize(key)];
        var val =  options.postFilter(asset);
        return match.replace(src, val || match);
     });

     if(original !== css) {
        grunt.log.writeln('✔ '.green + file + (' was changed.').grey);
        grunt.file.write(file, css);
     }
  });
});