Asset Rev

A Twig extension for Craft CMS that helps you cache-bust your assets using configurable strategies.

Why?

In order to speed up the load time of your pages, you can set a far-future expires header on your images, stylesheets and scripts. However, when you update those assets you'll need to update their file names to force the browser to download the updated version.

Using a manifest file is the recommended approach - you can read up on why using query strings isn't ideal here.

Strategies

This plugin allows you to configure multiple cache-busting strategies for your asset filenames. The plugin comes with three strategies out of the box:

Manifest File

css/main.css will be replaced with the corresponding hashed filename as defined within your assets manifest .json file.

If the contents of your manifest file are...

{
    "css/main.css": "css/main.a9961d38.css",
    "js/main.js": "js/main.786087f5.js"
}

then rev('css/main.css') will expand to css/main.a9961d38.css.

Query String

Append a query string to your file, based on the time it was last modified. For example: rev('css/main.css') will expand to something like css/main.css?1473534554.

Passthrough

Returns the original filename, without modification. This is useful if all other cache-busting strategies fail.

Strategy Pipeline

Pipelines allow you to attempt multiple cache-busting strategies in sequence. If one strategy fails, the plugin can proceed to try and cache-bust the asset filename using the next strategy in the pipeline.

The default pipeline is manifest|querystring|passthrough and will:

1. Attempt to use the ManifestFileStrategy. If it can’t, because the manifest file doesn’t exist, it will throw a ContinueException that defers cache-busting to the next strategy in the pipeline…
2. Attempt to use the QueryStringStrategy. If it can’t, because it can’t find the asset file, it will throw another ContinueException that defers cache-busting to the final default strategy…
3. Returns the original filename using the closure-based pass-through strategy.

Need to provide your own cache-busting logic? Simply create your own implementation of the Strategy class or define a Closure in the configuration file.

Installation

Install via the Plugin Store within your Craft 3 installation or using Composer: composer require clubstudioltd/craft-asset-rev

Configuration

The plugin comes with a config.php file that defines some sensible defaults.

If you want to set your own values you should create a assetrev.php file in your Craft config directory. The contents of this file will get merged with the plugin defaults, so you only need to specify values for the settings you want to override.

Strategies

strategies is where you define the strategies you'd like to try to rev your asset filename. You can provide the name of a class that implements StrategyContact or a custom closure. The defaults should cater to most requirements.

Pipeline

pipeline allows you to set the order of the configured strategies you'd like to try when revving your asset file names. The default of: manifest|querystring|passthrough should be adequate for most use-cases.

Manifest Path

manifestPath is where Craft should look for your manifest file. Non-absolute paths will be relative to the base path of your Craft installation (whatever CRAFT_BASE_PATH is set to).

Assets Base Path

assetsBasePath is the the base path to your assets. Again, this is relative to your craft base directory, unless you supply an absolute directory path.

Asset Url Prefix

assetUrlPrefix will be prepended to the output of rev().

Note: You can use any environment variables that you may have set in your general.php config file in any of these configuration values.

An Example Config File

<?php
return array(
    '*' => array(
        'strategies' => [
            'manifest' => \club\assetrev\utilities\strategies\ManifestFileStrategy::class,
            'querystring' => \club\assetrev\utilities\strategies\QueryStringStrategy::class,
            'passthrough' => function ($filename, $config) {
                return $filename;
            },
        ],
        'pipeline' => 'manifest|querystring|passthrough',
        'manifestPath' => 'resources/assets/assets.json',
        'assetsBasePath' => '../public/build/',
        'assetUrlPrefix' => '{baseUrl}',
    ),
);

Usage

Once activated and configured you can use the rev() function in your templates.

<link rel="stylesheet" href="{{ rev('css/main.css') }}">

Custom Strategies

Need to provide your own cache-busting logic? Create your own Strategy class or simply use a Closure.

Example Strategy Class

<?php

namespace your\namespace;

use club\assetrev\utilities\Strategy;
use club\assetrev\exceptions\ContinueException;

class QueryStringStrategy extends Strategy
{
    public function rev($filename)
    {
        // add your logic to manipulate $filename here...
        return $filename;
    }
}

Example Closure

Your method will have access to the asset filename and the plugin configuration array.

function ($filename, $config) {
    // add your logic to manipulate $filename here...
    return $filename;
}