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Mojolicious::Plugin::AssetPack::Guides::Tutorial(3pm) User Contributed Perl Documentation Mojolicious::Plugin::AssetPack::Guides::Tutorial(3pm)


Mojolicious::Plugin::AssetPack::Guides::Tutorial - AssetPack tutorial


This guide will give detailed information about how to define assets and include them into your templates.

See "DESCRIPTION" in Mojolicious::Plugin::AssetPack for a short description of AssetPack.


Loading the plugin

The plugin needs to be installed an loaded before any assets can be defined:

  $app->plugin(AssetPack => \%args);

Details about %args can be found under "register" in Mojolicious::Plugin::AssetPack, but there is one mandatory argument worth noting: "pipes". "pipes" need to be a list of all the pipes you need to process your assets. Example:

  $app->plugin(AssetPack => {pipes => [qw(Sass Css Combine)]});

Loading the plugin with the list above will enable AssetPack to process Sass and Css files, minify them and combine them into a single asset in production.

Optional dependencies

AssetPack has only optional dependencies. The reason for that is that the dependencies should only be required while developing, and not for running the application. See <> for a complete list, but here are the current list:

  • CSS::Minifier::XS 0.09

    Used to minify CSS.

  • CSS::Sass 3.3.0

    Used to process and minify CSS.

  • Imager::File::PNG 0.90

    TODO: Used to generate CSS sprites.

  • JavaScript::Minifier::XS 0.11

    Used to minify JavaScript.


AssetPack does not do any heavy lifting itself: All the processing is left to the pipe objects.

  • Mojolicious::Plugin::AssetPack::Pipe::CoffeeScript

    Process CoffeeScript coffee files. Should be loaded before Mojolicious::Plugin::AssetPack::Pipe::JavaScript.

  • Mojolicious::Plugin::AssetPack::Pipe::Combine

    Combine multiple assets to one. Should be loaded last.

  • Mojolicious::Plugin::AssetPack::Pipe::Css

    Minify CSS.

  • Mojolicious::Plugin::AssetPack::Pipe::Favicon

    There is a special topic called "favicon.ico", combined with the Mojolicious::Plugin::AssetPack::Pipe::Favicon pipe which can be used to describe favicons, touch icons and tile icons.

  • Mojolicious::Plugin::AssetPack::Pipe::Fetch

    Will look for "url(...)" in CSS files and download the related assets.

  • Mojolicious::Plugin::AssetPack::Pipe::JavaScript

    Minify JavaScript.

  • Mojolicious::Plugin::AssetPack::Pipe::Jpeg

    Used to crush "jpeg" image files.

  • Mojolicious::Plugin::AssetPack::Pipe::Less

    Process Less CSS files. Should be loaded before Mojolicious::Plugin::AssetPack::Pipe::Css.

  • Mojolicious::Plugin::AssetPack::Pipe::Png

    Used to crush "png" image files.

  • Mojolicious::Plugin::AssetPack::Pipe::Riotjs

    Process <> tag files. Should be loaded before Mojolicious::Plugin::AssetPack::Pipe::JavaScript.

  • Mojolicious::Plugin::AssetPack::Pipe::Sass

    Process sass and scss files. Should be loaded before Mojolicious::Plugin::AssetPack::Pipe::Css.

Where to place source files

The source/input files that make up a virtual asset (topic) can come from either...

On disk

AssetPack will look for source files in the "assets" directory, relative to the application home. Unlike the "public" directory, this directory is not shared on the internet, but the generated assets will still be available thanks to a custom route.

Mojolicious::Plugin::AssetPack::Store is a sub class of Mojolicious::Static, allowing it to find files relative to "paths" in Mojolicious::Static. For example, to change asset search paths, you can do:

    $app->asset->store->paths(["/some/new/location", "/other/location"]);

DATA section

Mojolicious::Plugin::AssetPack::Store is a sub class of Mojolicious::Static, allowing it to look for files in DATA sections of "classes" in Mojolicious::Static.

The DATA section can also be used to lookup "@import" files. (Currently only supported by Mojolicious::Plugin::AssetPack::Pipe::Sass)


Any file starting with "http" or "https" will be downloaded from web using "ua" in Mojolicious::Plugin::AssetPack.

It will also parse recursively "@import" files and download those as well. (Currently only supported by Mojolicious::Plugin::AssetPack::Pipe::Sass)

Assets from web will be cached locally to prevent downloading new and untested assets on each application startup.

Current Mojolicious application

See "DYNAMIC ASSETS" in Mojolicious::Plugin::Assets::Guides::Cookbook.

Process assets

Assets should be defined when you application starts. This can either be done using a definition file or inside you application.

Defining assets in the application

Assets can be defined using the "process" in Mojolicious::Plugin::AssetPack method:

    "app.css" => (

In the example above we have defined a topic named "app.css" which later can be included in templates. The list of files following are the source files which will make up the final asset.

Defining assets in a definition file

Moving the definition to an external file can be useful for keeping the application code tidy. The definition file should be located in the assets directory, or optionally defined it in the "DATA" section. The default file is called "assetpack.def" and will be looked up if "process" in Mojolicious::Plugin::AssetPack is called without arguments. Example file:

  ! app.css
  < sass/bar.scss
  < sass/main.scss

Empty lines and lines starting with "#" will be skipped. Each line starting with "!" will be used to define a topic (virtual asset name), and "<" will define a source file. This means that the file above will result in (almost) the same as in the example above.

The idea of the line starting with "<<" is to download an external (remote) file for your convenience, which can be imported in your SASS/LESS files. The downloaded file is not included in the output asset. For example, you have "sass/main.scss" which depends on "materialize.scss" (remote file) and you need this "materialize.scss" file locally available to be imported in "sass/main.scss". If you want to include a remote file in your output asset, use '<' insteaf of '<<'.

It is also possible to add conditions:

  ! app.css
  < development.css [mode==development] [minify==0]
  < production.css  [mode!=development]

"development.css" will be processed if "mode" in Mojolicious is "development" and "minify" in Mojolicious::Plugin::AssetPack is "0". "production.css" will be processed if "mode" in Mojolicious is something else than "development". This is especially useful if you want to include a JavaScript with debug flags set while developing, but switch to a smaller version without debug in production.

Using assets

Any processed asset can be accessed by referring to a topic.


An asset can be included in a template using the "asset" in Mojolicious::Plugin::AssetPack helper:

    %= asset "app.css"
    %= asset "app.js"

The "asset" in Mojolicious::Plugin::AssetPack helper takes additional arguments which will be passed on directly to either the "javascript" in Mojolicious::Plugin::TagHelpers helper or "stylesheet" in Mojolicious::Plugin::TagHelpers helper. Example:

    %= asset "app.css", media => "print"

In production mode, the helper above will just result in one "link" tag. On the other hand, if you are in "development" mode, it will result in on "link" tag per source asset.

Asset objects

It is also possible to retrieve the processed asset objects. The example below will retrieve a Mojo::Collection object holding zero or more Mojolicious::Plugin::AssetPack::Asset objects:

  my $collection = $app->asset->processed("app.css");
  print $collection->map("checksum")->join(", ");

This can also be used to inline assets in a template:

  %= stylesheet sub { asset->processed('app.css')->map('content')->join }

Application mode

The application mode will define if the assets should be combined and minified. The "minify" in Mojolicious::Plugin::AssetPack attribute can also be set manually if you have special needs.


The assets will be processed, but not minified/combined if MOJO_MODE or "mode" in Mojolicious is set to "development". This is to make it easier to map JavaScript or CSS bugs to a specific file and line. "development" is the default mode while running morbo:

  $ morbo -w assets/ -w lib/ -w templates/ script/myapp

Any other mode

Any "production" mode will result in one combined and minified asset. This will save bandwidth and roundtrip time to the server.


Processed assets will be cached to disk when possible. The process step is run so if such a processed asset exists, the process step will not be run again. Again, the external tools (less, coffee, ...) and modules (JavaScript::Minifier::XS, CSS::Sass) will only be required while developing, but can be skipped when installing an already built application.

Assets without topics

One nifty feature is to use Mojolicious::Plugin::AssetPack for assets which do not have any pipe to process them. The reason why this comes in handy is to avoid cache issues, since changing the file on disk will generate a new URL.

These assets can also be defined directly in the templates, without having to be defined in the application startup process. Examples:

  # <img src="/asset/52e98718f0/foo.gif">
  %= asset "/image/foo.gif"
  # <img src="/asset/87652910af/baz.svg">
  %= asset "/image/baz.svg"
  # <link rel="icon" href="/asset/65428718f1/bar.ico">
  %= asset "/image/bar.ico"
  # <source src="/asset/87652718f0/baz.mp3" type="audio/mpeg">
  %= asset "/audio/baz.mp3"
  # <source src="/asset/52e87652f0/foo.mp4" type="video/mp4">
  %= asset "/video/foo.mp4"
  # <source src="/asset/52eaz7613a/bar.ogg" type="audio/ogg">
  %= asset "/audio/bar.ogg"
  # <source src="/asset/baf72618f1/foo.ogv" type="audio/ogv">
  %= asset "/video/foo.ogv"
  # <source src="/asset/92118711f0/bar.webm" type="audio/webm">
  %= asset "/video/bar.webm"


Mojolicious::Plugin::AssetPack, Mojolicious::Plugin::AssetPack::Guides::Developing and Mojolicious::Plugin::AssetPack::Guides::Cookbook.

2021-09-30 perl v5.32.1