3rd party dependency conflict in developing Wordpress Plugin

Question

I am developing a plugin that used composer.. meaning it has a vendor folder inside the plugin folder which includes Guzzle HTTP dependency

On wordpress site we installed this plugin, there is an existing plugin that has Guzzle HTTP

Now when we activate this plugin i am getting an error something like this:

Fatal error: Cannot redeclare GuzzleHttp\uri_template() (previously declared in /nas/content/staging/project/wp-content/plugins/my-plugin/vendor/guzzlehttp/guzzle/src/functions.php:17) in /nas/content/staging/project/wp-content/plugins/other-plugin/includes/lib/aws-sdk/GuzzleHttp/functions.php on line 31

I tried installing Plugins Load Order to force the 'other-plugin' to load first before 'my-plugin' currently the error is happening on the other-plugin's resources. this way, The error will yield in our autoload and we can catch that.

unfortunately.. Plugins Load Order did not work..

any ideas how to solve this?

Answer 1

Welcome to WordPress hell. We have 2018 and WordPress still does not have any dependency management and still didn't notice Composer existence.

WordPress ecosystem simply relies on assumption, that functions/classes names of plugins/themes should be unique. Obviously distributing popular 3rd-part Composer libraries with your plugin/theme is asking for trouble - it is easy to get names collision when other plugin is doing the same. There is no good way out of this situation.

If you want a bulletproof solution for standalone plugins, you should prefix namespaces of every package in your vendor directory with plugin prefix, for example myplygin\vendor. Then GuzzleHttp\Client becomes myplugin\vendors\GuzzleHttp\Client, so there is no risk of name collisions. This will require some work to write script for this (or you may use some existing solutions, like humbug/php-scoper), and you may get many duplicated dependencies (10 plugins may bring the same library 10 times, but with different namespaces), but this is the cost of integrating modern tools and patterns into outdated software.

If you're writing this plugin for yourself and you're controlling final installation, you may try to use Composer for installing WordPress and its plugins. You still may need to fix 3rd-party plugins (via forking) if they're have bundled some composer library, but in the long run it should simplify many things and you may avoid duplicating libraries for every plugin.

Answer 2

By design, PHP and Composer assume that you develop and distribute your code in a controlled environment. However, when you publish plugins on WordPress or modules on Joomla, you distribute the code on systems where you don't have control over what other authors install. This situation can result in name collisions such as Cannot redeclare GuzzleHttp\uri_template()....

To prepare your code for multi-vendor setups, you must prefix the PHP code to avoid name collisions or version collisions (the same library with a different version is loaded first). For instance, Guzzle is a well-known and widely used library, so if you publish a plugin including it, you must prefix it before distribution.

At first glance, you may think that prefixing only the namespaces would get the job done. But other named elements such as global functions and traits must also be prefixed to avoid all possible error types.

To prefix PHP code, there are tools or services to execute the task:

• humbug/php-scoper. Prefixes all PHP namespaces in a file/directory to isolate the code bundled in PHARs.
• Interfacelab/namespacer. Namespacer allows you to rename the namespace of any composer packages. It works by adding a namespace prefix to all of the namespaces. Namespacer also prefixes the package names. It then generates a folder called "lib" that you can safely include in your WordPress plugin.
• coenjacobs/mozart. Developers tool for WordPress plugins: Wraps all your projects dependencies in your own namespace. This prevents conflicts with other plugins that load the same dependencies but in different versions.
• PHP-Prefixer. It's an automated online service powered by a complex rule-based system to apply prefixes to Composer dependencies. In the composer.json, you just define the prefix to apply without worrying about the nitty-gritty details.

Disclaimer: I'm the lead PHP-Prefixer developer.

Answer 3

This is not suggested but use it if you must

function this_plugin_last() {
    $wp_path_to_this_file = preg_replace('/(.*)plugins\/(.*)$/', WP_PLUGIN_DIR."/$2", __FILE__);
    $this_plugin = plugin_basename(trim($wp_path_to_this_file));
    $active_plugins = get_option('active_plugins');
    $this_plugin_key = array_search($this_plugin, $active_plugins);
        array_splice($active_plugins, $this_plugin_key, 1);
        array_push($active_plugins, $this_plugin);
        update_option('active_plugins', $active_plugins);
}
add_action("activated_plugin", "this_plugin_last");