Plugin's "Update Now" not working - Installed in folder with random suffix

Question

When I click on "Update now" the plugin gets installed, but I'm getting the following error:

The plugin "test/test.php" has been deactivated due to an error: Plugin file does not exist.

Also, I can see on the file structure the plugin has been installed using a random suffix (test-wmAX6O) instead of just using test for the folder name.

I'm returning the following on check_for_plugin_update:

$plugin_info = array(
    'slug'        => 'test',
    'id'          => 'test/test.php',
    'plugin'      => 'test/test.php',
    'new_version' => $remote_version->version,
    'url'         => $remote_version->info_url,
    'package'     => $remote_version->download_url,
    'requires_php'  => '',
    'compatibility' => new stdClass(),
);

$checked_data->response['test/test.php'] = (object) $plugin_info;

return $checked_data;

Which gets called in the main file test/test.php in the constructor:

public function __construct() {
         ....
    $this->force_plugin_update_check();

    add_action( 'pre_set_site_transient_update_plugins',  array($this, 'check_for_plugin_update') );
}

function force_plugin_update_check(){
  delete_site_transient('update_plugins');
  wp_update_plugins();  // Force a fresh update check
}

The plugin's main file test/test.php also contains the following header comments:

<?php
/**
* Plugin Name: Test
* Plugin URI: https://test.io
* Description: A brief description of the plugin.
* Text Domain: test
* Version: 1.1.1
* Author: XXXX
* Author URI: https://test.io

* License: GPL2
* @package test
**/

Am I missing something?

It looks like there's a problem with the "slug" but I can't see why.

I can't find any good documentation on pre_set_site_transient_update_plugins anywhere on WordPress, so I'm a bit lost here.

Answer 1

I tried the hook update_plugins_{$hostname} following the fresher informations I found in the link quoted by Tom J Nowell :
https://make.wordpress.org/core/2021/06/29/introducing-update-uri-plugin-header-in-wordpress-5-8/

here is a example of plugin with self managed update. it's a base for update by the Updates page and the Plugins page and this example can be complete to manage more details, e.g. in the plugin information page. then don't hesitate to edit to complete.

<?php
/*
Plugin Name: MY_PLUGIN
Version: 128
Plugin URI: https://my_domain.com/my_plugin
Update URI: https://my_domain.com/my_plugin
*/

if (!function_exists("add_action")) {
    echo "plugin";
    exit();
}

// the part "my_domain.com" in the hook is the domain of the url in the header "Update URI"
add_filter("update_plugins_my_domain.com", function ($update, $plugin_data, $plugin_file, $locales) {
    
    // if you manage more plugins on the same domain,
    //     test here if it's the current plugin
    
    
    if (TRUE) { // if there is a new version for this plugin
        $update = [
            "slug" => "MY_PLUGIN",
            "version" => 137, // new version
            "package" => "https://my_domain.com/plugins-updates/my_plugin-v137.zip",
        ];
    }
    
    
    return $update;
    
}, 10, 4);


// filter to manage the information page of the plugin
add_filter("plugins_api", function ($res, $action, $args) {
    
    if (    ("plugin_information" === $action)
        &&  ("MY_PLUGIN" === $args->slug)
    ) {
        
        $res = (object) [
            "slug" => $args->slug,
            "name" => "Name of the plugin",
            "sections" => [
                "description" => "<strong>plugin information</strong>",
                "changelog" => "<ul><li>details of the change log</li></ul>",
            ],
            "banners" => [
                "low" => "https://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/8_Poultry.jpg/1024px-8_Poultry.jpg",
            ],
            "download_link" => ".", // just any single character is enough
            // to enable update button on information page
        ];
        
    }
    
    
    return $res;
    
}, 10, 3);