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Asset compilers and processors

The asset building process consists of multiple steps. At it's simplest, only the directives are processed and dependencies are included into the build files. The build process can do much more though, like compiling less files with lessjs or compressing js files with uglifyjs.

Each build follows these fives steps that can be customized for your environment.

  1. Preprocess
  2. Compile
  3. Postprocess
  4. Compress
  5. Save to filesystem

1. Preprocess

The first step is where dependencies are managed. Gears looks for directives within assets and includes them within the asset file. As explained elsewhere, directives are simple comments in the header of script or css files. For example:

/*
 *= require jquery
 *= require underscore
 *= require backbone
*/

It's not common to change the preprocess step, but if you wish to do so, this can be done by modifying the :setting:`GEARS_PREPROCESSORS` setting.

2. Compile

The second step compiles source files like CoffeeScript, Stylus, or Less into javascript and css. Compilers are defined in the :setting:`GEARS_COMPILERS` setting.

Various compilers are just a pip install away. You can browse plugins that are available at the Gears repositories github page. If you find a compiler not supported, it's easy to create a plugin of your own.

3. Postprocess

The third step is where files are postprocessed. By default, Django Gears runs the gears.processors.HexdigestPathsProcessor for css files. This processor replaces url declarations in the css with fingerprinted versions. Note, this processor only works if all paths in url declarations refer to local files.

The post processors can be modified with the :setting:`GEARS_POSTPROCESSORS` setting.

4. Compress

The fourth step is where tools like SlimIt, UglifyJS, or clean-css are run. These produce minified files and minimize bandwidth requirements.

For users of Python 2.X, Gears has built-in support for SlimIt and cssmin.

Other compilers are just a pip install away. You can browse plugins that are available at the Gears repositories github page.

5. Save to filesystem

The fifth step is where processed files are saved to the file system. The destination directory is controlled by the :setting:`GEARS_ROOT` setting.

Unless :setting:`GEARS_FINGERPRINTING` is set to false, the asset will be fingerprinted and added to the .manifest.json file.

During this step, the file can optionally be gzipped. This is controlled by the :setting:`GEARS_GZIP` setting.