Compile LESS to CSS. Adds experimental features that extend Less.js for maintaining UI components and themes. From Jon Schlinkert, core team member of Less.js.

This project is a fork of the popular grunt-contrib-less by the talented Tyler Kellen. Please use that plugin if you require something stable and dependable.

This plugin requires Grunt ~0.4.2

If you haven't used Grunt before, be sure to check out the Getting Started guide, as it explains how to create a Gruntfile as well as install and use Grunt plugins. Once you're familiar with that process, you may install this plugin with this command:

npm install assemble-less --save-dev

Once the plugin has been installed, it may be enabled inside your Gruntfile with this line of JavaScript:

grunt.loadNpmTasks('assemble-less');

Run this task with the grunt less command.

Task targets, files and options may be specified according to the grunt Configuring tasks guide.

Type: String

Default: null

A convenience option for externalizing task options into a .lessrc or .lessrc.yml file. If this file is specified, options defined therein will be used.

Type: Object

Default: undefined

Prepend variables to source files.

Type: Object

Default: undefined

Append variables to source files.

Type: String|Array

Default: Empty string

Pass metadata as context to Lo-Dash templates embedded in LESS files. The name of the files is used as the first path in the template variables, so if you want to use data from palette.yml, your templates would look something like: <%= palette.foo %>.

Data may be formatted in JSON, YAML. See this YAML example and this LESS example.

Note that data passed into options.metadata is merged at the task and target levels. You can turn this off by adding options: {merge: false}, which then disables merging and allows targets to override any data passed in at the task-level.

Type: Object (each option accepts a String or Array)

Default: null

Prepend @import statements to src files using any of the new @import directives released after Less.js v1.5.0, less, css, inline, reference (multiple and once probably aren't applicable here, but feel free to use them if you find a use case). See examples.

Any new import directives will be immediately available upon release by Less.js.

Type: Boolean|Object

Default: false

Process source files as templates before concatenating.

• false - No processing will occur.
• true - Process source files using grunt.template.process defaults.
• options object - Process source files using grunt.template.process, using the specified options.
• function(src, filepath) - Process source files using the given function, called once for each file. The returned value will be used as source code.

(Default processing options are explained in the grunt.template.process documentation)

Type: String

Default: Empty string

This string will be prepended to the beginning of the concatenated output. It is processed using grunt.template.process, using the default options.

(Default processing options are explained in the grunt.template.process documentation)

Type: Boolean|Object

Default: false

Strip JavaScript banner comments from source files.

• false - No comments are stripped.
• true - /* ... */ block comments are stripped, but NOT /*! ... */ comments.
• options object:
  • By default, behaves as if true were specified.
  • block - If true, all block comments are stripped.
  • line - If true, any contiguous leading // line comments are stripped.

Type: String|Array

Default: Directory of input file.

Specifies directories to scan for @import directives when parsing. The default value is the directory of the specified source files. In other words, the paths option allows you to specify paths for your @import statements in the less task as an alternative to specifying a path on every @import statement that appears throughout your LESS files. So instead of doing this:

@import "path/to/less/files/mixins.less";

you can do this:

@import "mixins.less";

Type: String

Default: ""

A path to add on to the start of every url resource.

Type: Boolean

Default: false

Compress output by removing some whitespaces.

Type: Boolean

Default: false

Compress output using clean-css.

Type: Boolean

Default: true

Enforce the css output is compatible with Internet Explorer 8.

For example, the data-uri function encodes a file in base64 encoding and embeds it into the generated CSS files as a data-URI. Because Internet Explorer 8 limits data-uris to 32KB, the ieCompat option prevents less from exceeding this.

Type: Integer

Default: null

Set the parser's optimization level. The lower the number, the less nodes it will create in the tree. This could matter for debugging, or if you want to access the individual nodes in the tree.

Type: Boolean

Default: false

Force evaluation of imports.

Type: Boolean

Default: false

When enabled, math is required to be in parenthesis.

Type: Boolean

Default: false

When enabled, less will validate the units used (e.g. 4px/2px = 2, not 2px and 4em/2px throws an error).

Type: Boolean

Default: false

Read @import'ed files synchronously from disk.

Type: String

Default: false

Configures -sass-debug-info support.

Accepts following values: comments, mediaquery, all.

Type: Boolean

Default: false

Rewrite urls to be relative. false: do not modify urls.

Type: Object

Default: none

Define custom functions to be available within your LESS stylesheets. The function's name must be lowercase and return a primitive type (not an object or array). In the function definition, the first argument is the less object, and subsequent arguments are from the less function call. Values passed to the function are not simple primitive types, rather types defined within less. See the LESS documentation for more information on the available types.

Choices: false|'min'|'gzip'

Default: false

Either do not report anything, report only minification result, or report minification and gzip results. This is useful to see exactly how well Less is performing, but using 'gzip' can add 5-10x runtime task execution.

Example ouput using 'gzip':

Original: 198444 bytes.
Minified: 101615 bytes.
Gzipped:  20084 bytes.

Type: Boolean

Default: false

Enable source maps.

Type: String

Default: none

Write the source map to a separate file with the given filename.

Type: String

Default: none

Override the default url that points to the sourcemap from the compiled css file.

Type: String

Default: none

Sets the base path for the less file paths in the source map.

Type: String

Default: none

Adds this path onto the less file paths in the source map.

Type: Boolean

Default: false

Puts the less files into the map instead of referencing them.

Type: String

Default: less (current release)

Specify the directory containing the version of Less.js to use for compiling. You may specify a version at the task level or a different version for each target.

less: {
  options: {
    version: 'vendor/less'
  },
  styles: {
    files: {
      'css/style.css': ['src/style.less']
    }
  }
}

Useful for testing new features included in a beta or alpha release, or for comparing the compiled results from different versions of Less.js.

Basic config for compiling LESS to CSS.

less: {
  development: {
    options: {
      paths: ["assets/css"]
    },
    files: {
      "path/to/result.css": "path/to/source.less"
    }
  },
  production: {
    options: {
      paths: ["assets/css"],
      compress: true
    },
    files: {
      "path/to/result.css": "path/to/source.less"
    }
  }
}

A .lessrc file must contain valid JSON and look something like this:

{
  "compress": true,
  "metadata": "src/*.{json,yml}",
  "paths": ["vendor/bootstrap/less"]
}

A .lessrc.yml must contain valid YAML and look something like this:

compress: true
paths:
- vendor/bootstrap/less

Prepend @import statements to src files using any of the new @import directives released after Less.js v1.5.0.

Options are:

• reference: use a less file but do not output it
• inline: include the source file in the output but do not process as less
• less: treat the file as a less file, no matter what the file extension
• css: treat the file as a css file, no matter what the file extension

less: {
  options: {
    paths: 'vendor/bootstrap/less',
    imports: {
      reference: ['variables.less', 'mixins.less'],
      inline: ['normalize.css'],
      less: ['normalize.css'],
      css: ['foo.css', 'bar.css']
    }
  },
  files: {}
}

Use import directives to compile each Bootstrap's LESS components separately.

Using the imports: {} option and the "files array format" enables us to compile each Bootstrap LESS component without having to add @import "variables.less"; and @import "mixins.less"; to every file.

less: {
  options: {
    paths: 'vendor/bootstrap/less',
    imports: {
      reference: ['variables.less', 'mixins.less'],
    }
  },
  components: {
    files: [
      { expand: true, cwd: 'vendor/bootstrap/less', src: '*.less', dest: 'assets/css/', ext: '.css' }
    ]
  }
}

Use the metadata option to pass context to Lo-Dash templates before compiling. For example, let's say you have a config like this:

less: {
  options: {
    metadata: 'src/*.{json,yml}'
  },
  styles: {
    files: {
      'css/style.css': ['src/style.less']
    }
  }
}

and a data file, palette.yml, with some variables defined:

## palette.yml
info:    '#000'
warning: '#111'
danger:  '#222'
success: '#333'

Then in our LESS file:

// Use as values to variables
@palette-info:    <%= palette.info %>;
@palette-warning: <%= palette.warning %>;

.swatch-info {
  background: @palette-info;
}
.swatch-warning {
  background: @palette-warning;
}

// or directly as variables
.swatch-danger {
  background: <%= palette.danger %>;
}
.swatch-success {
  background: <%= palette.success %>;
}

• 2014-01-01   v0.7.0   Update to use the Less.js v1.6.0 API for banner, globalVars and modifyVars.
• 2013-12-18   v0.6.0   Adds globalVars and modifyVars options. See readme and Gruntfile for examples. Support sourceMapURL Support outputSourceFiles Support sourceMapFilename, sourceMapBasepath and sourceMapRootpath Upgrade to LESS 1.5 Support strictUnits option Support sourceMap option Add customFunctions option for defining custom functions within LESS Output the source file name on error yuicompress option now cleancss (Less changed underlying dependency)
• 2013-07-30   v0.5.0   Completely refactored the plugin based on grunt-contrib-less. Add examples for all features to Gruntfile. Removed the concat feature. You can now use .lessrc or .lessrc.yml for externalizing task options. New stripBanners option
• 2013-06-13   v0.4.7   Cleaned up a lot of the Gruntfile. Examples are more clear. New import option for prepending import statements to LESS files before compiling. New banner option for adding banners to generated CSS files.
• 2013-03-17   v0.3.0   New option to specify the version of less.js to use for compiling to CSS.
• 2013-03-14   v0.2.3   New options from Less.js 1.4.0
• 2013-02-27   v0.1.0   First commit.

This project is a fork of the popular grunt-contrib-less by Tyler Kellen. Please use that plugin if you require something stable and dependable.

This fork is maintained by:

Jon Schlinkert

• github/jonschlinkert
• twitter/jonschlinkert

Brian Woodward

• github/doowb
• twitter/doowb

Copyright (c) 2014 Jon Schlinkert, contributors. Released under the MIT license

This file was generated by grunt-readme on Wednesday, January 1, 2014.