Multipass Compilation

Roots stands alone among static site compilers in its ability to handle multipass compilation, meaning that a single file can be compiled multiple times to determine the output. While not a common use-case for most builds, multipass compilation can be a very powerful tool for some advanced setups.

To compile a file for multiple languages, you can just add another extension. For example, if you wanted a file to be compiled in ejs then jade, you could call the file example.jade.ejs, and as long as both compilers are installed, it will work.

If you want to use a CSS preprocessor like stylus in conjunction with postcss, you need to perform an additional step. First you need add the extension .css to your master.styl like so: master.css.styl. Then adjust your

css_pipeline(files: 'assets/css/*.styl', postcss:true),


  use: [lost()]

Note that postcss and lost need to be installed, or roots will throw an error your way. In the following section we take a look at how exactly roots treats the file extensions we just added.

File Extension Logic

Roots abides by a set of rules when processing and outputting file extensions. If you are confused about why a certain file has a certain extension after being compiled, this is probably the section you are looking for.

First, if a file has no extensions that are compiled at all, it is copied exactly to the output folder without being changed. The only time extensions are modified is when one or more of a file's extensions match to an installed and supported compiler. Roots uses accord for all compilation under the hood, and you can see the list of supported languages there.

If you have an extension that maps to an accord-supported compiler and that package has been installed through your package.json file, the file will be compiled. If the first extension after the filename is compiled, that compiler's output target will be the sole output extension for the file every time. For example, will always output example.html, since jade is the first extension and .html is jade's output target. If you think about it, this makes sense, since the foo and bar extensions need to compile into a format that jade would be able to parse without error.

If the first extension after the filename is not compiled, it will take that extension no matter what. For example, if you had a file called, it would compiled to example.html every time, regardless of any compiled or non-compiled extensions following it. So the overall lesson to learn here is that the first extension is the only one that matters when determining the output extension.

It's worth noting that for roots, there's no such thing as dots in filenames. Since roots parses multiple extensions, if you put a dot in a filename, it's treated as an extension. Dots should not be in filenames anyway, but that's a separate debate. So for example if for some very strange reason, you had a file called, it would output example.min, because .min is the first extension, and is not compiled. If this example concerns you, take note of two things. First, coffeescript doesn't output minified code, so having .min in the filename would technically be incorrect. You can always minify the file and modify the extension through a roots extension intended for concatenating and minifiying files. Second, if you have a whatever.min.js file in your project, it will output correctly because neither min or js are compiled, so the file and its extensions will just be copied.

Finally, if you have a .jade file in your project for example, but have not installed the jade package through your package.json file, it will be treated as a static file and copied with the .jade extension intact.