grunt replace all less files into css files

Question

I use grunt to convert all my less files into css files,using this:

less: {
  development: {
    files: {
      "css/*.css": "less/*.less"
    }
  }
}

This worked on version 0.3.0, but now that I have upgraded to v0.4.0 it doesn't work anymore.

The following code (not using * in the destination) works on both versions, so the problem is with the star on the destination file.

less: {
  development: {
    files: {
      "css/test.css": "less/*.less"
    }
  }
}

Any idea ?

Answer 1

This isn't a bug. Grunt no longer supports globbing in dest using that configuration. However, you can use the "files array" format, like this:

files: [
  {
    expand: true,
    cwd: 'src',
    src: ['*.less'],
    dest: 'assets/css/',
    ext: '.css'
  }
]

Also, if you use a library like Bootstrap and you want to build each LESS file (component) into a separate, individual CSS file, it's not very easy to accomplish "out of the box". The reason is that each LESS file would need to have its own @import statements for variables.less and mixins.less (and a couple of others like forms.less and navbar.less, since they are referenced in other files).

To make this really easy, try the Grunt plugin, assemble-less (disclaimer: I'm one of the maintainers of the project, and I'm also on the core team for less.js). assemble-less is a fork of grunt-contrib-less by Tyler Kellen, but it adds some experimental features that will accomplish what you need (if you want stability, please stick with grunt-contrib-less). For example:

// Project configuration.
grunt.initConfig({

  less: {
    // Compile all targeted LESS files individually
    components: {
      options: {
        imports: {
          // Use the new "reference" directive, e.g.
          // @import (reference) "variables.less";
          reference: [
            "bootstrap/mixins.less", 
            "bootstrap/variables.less" 
          ]
        }
      },
      files: [
        {
          expand: true,
          cwd: 'bootstrap/less',
          // Compile each LESS component excluding "bootstrap.less", 
          // "mixins.less" and "variables.less" 
          src: ['*.less', '!{boot,var,mix}*.less'],
          dest: 'assets/css/',
          ext: '.css'
        }
      ]
    }
  }
  ...
}

The imports feature essentially prepends the specified @import statements onto the source files. The reference option allows you to "reference" other less files while only outputting styles that are specifically referenced via mixins or :extend. You might need to reference a few more files than shown here, since Bootstrap cross-references styles from other components, like forms.less, buttons.less, etc. (See the Gruntfile in assemble-less for examples.)

So after running the assemble-less task with the configuration in the example above, the assets/css folder would have:

• alerts.css
• badges.css
• breadcrumbs.css
• button-groups.css
• buttons.css
• carousel.css
• close.css
• code.css
• component-animations.css
• dropdowns.css
• forms.css
• glyphicons.css
• grid.css
• input-groups.css
• jumbotron.css
• labels.css
• list-group.css
• media.css
• modals.css
• navbar.css
• navs.css
• normalize.css
• pager.css
• pagination.css
• panels.css
• popovers.css
• print.css
• progress-bars.css
• responsive-utilities.css
• scaffolding.css
• tables.css
• theme.css
• thumbnails.css
• tooltip.css
• type.css
• utilities.css
• wells.css

There are other features that should help you with this, but the imports feature is super powerful since it allows you to add directives directly to the Gruntfile.