Assets Bundling

Hugo version 0.43 bundled a very VERY POWERFUL feature: the assets processing function. This function allows you bundle any css or js into a single bundle css or js file, alongside with fingerprint integrity checking, all directly from Hugo itself!

That is a +2 for Hugo.

Shifting To Assets Directory

As of current status, you can only use assets processing function against assets directory.

The default is ./assets. For your local site, you can configure it using the assetDir keyword.

For theme modules however, you do not have a choice but to use the default ./assets directory.

Opinion

After testing the function out in my Bissetii theme module, I agree with the development team that those assets should stay inside the assets directory. They are not static files but are as internal resources files to build for one. Hence, I would not recommend you to alter assetDir location unless otherwise absolute necessary.

Compressing Assets

There are 3 stages for compressing an assets:

forming the list
compress the resources
link the process asset

Forming the list

This is quite straightforward, all you need to do is form an assets list using slice function. Example:

{{- $assets := slice -}}

{{- $assets = $assets | append ( resources.Get "css/main.css" ) -}}

{{- $assets = $assets | append ( resources.Get "css/navbars/sidebar_from_left_with_opacity.css" ) -}}

{{- $assets = $assets | append ( resources.Get "css/footers/simple.css" ) -}}

{{- $assets = $assets | append ( resources.Get "css/typography.css" ) -}}

Remember to place all the files inside ./assets/css accordingly. Also, keep in mind that resources.Get know the differences between css and js. Hence, you can't simply mix them up.

Compress the Resources

Next is to compress the resources. It's a one-liner:

{{- $css := $assets | resources.Concat "myBundledCSSName.css" | resources.Minify | resources.Fingerprint "sha512" -}}

This generates the final output and save under $css (for javascript, you can use $js). If you notice, the list gathered previously are passed into 3 stages processing:

resources.Concat - bundle all the assets together into 1 file and name it according to the given name.
resources.Minify - minify the bundled asset file by stripping off necessary whitespace.
resources.Fingerprint - add a file integrity check with the minified bundled asset file.

Link it

Now that you have the asset, you can use it. Depending on your asset type, a typical linking would be:

<link rel="stylesheet"

      href="{{- $css.Permalink -}}"

      integrity="{{- $css.Data.Integrity -}}" />

Javascript

{{- if eq $mode "async" -}}

<script async type="text/javascript"

        src="{{ $js.Permalink }}"

        integrity="{{ $js.Data.Integrity }}"></script>

{{- else -}}

<script defer type="text/javascript"

        src="{{ $js.Permalink }}"

        integrity="{{ $js.Data.Integrity }}"></script>

{{- end -}}

Optionally: Inline into HTML

To inline into HTML, you simply do:

<style type="text/css">

{{ $css.Content | safeCSS }}

</style>

Javascript

<script type="text/javascript">

{{ $js.Content | safeJS }}

</script>