How prevent STDOUT of Plugin_Upgrader->upgrade(...)?

Question

🖥️ Code

function my_custom_endpoint(WP_REST_Request $request)
{
  $plugin_file = $request->get_param("plugin_file");

  if(!class_exists('Plugin_Upgrader'))
  {
    require_once ABSPATH . 'wp-admin/includes/class-wp-upgrader.php';
  }

  ob_start();
  $upgrader = new Plugin_Upgrader();
  $result = $upgrader->upgrade($plugin_file);
  $logs = ob_get_clean();

  // I m testing here if the upgrade is successfull before return the response

  return rest_ensure_response(array("logs" => $logs));
}

⛔ The issue

I create a custom WordPress REST endpoint to update some plugin from another website.

The method Plugin_Upgrader::upgrade write a lot of strings in STDOUT, I wanna catch in $logs but when I try buffering it with ob_start I still get it in my http response.

<divclass="wrap">
<h1></h1>
<p>downloading_package</p>
<p>L’authenticitéde<spanclass="code">complianz-gdpr.6.5.4.zip</span>
n’apaspuêtrevérifiéecaraucunesignaturen’aététrouvée.</p>
<p>unpack_package</p>
<p>Installationdeladernièreversion&#8230;</p>
<p>remove_old</p>
<p>process_success</p>
</div>
<b>Warning</b>: Cannotmodifyheaderinformation-headersalreadysentby(outputstartedatC: \xampp\htdocs\oust\wp-includes\functions.php: 5349)in<b>C: \xampp\htdocs\oust\wp-includes\rest-api\class-wp-rest-server.php</b>online<b>1769</b><br/>
{
  'logs' => false
}

🇫🇷 French Logs Sorry

PHP ob_get_clean: If output buffering isn't active then false is returned.

This return seems to be the cause of all my problems, but I don't understand why buffering is deactivate after $upgrader->upgrade($plugin_file) call (I tried replace it with simple echo and the buffering work)..

🙆‍♂️ Expected

{
  "logs": "<divclass="wrap"><h1></h1><p>downloading_package</p><p>L’authenticitéde<spanclass="code">complianz-gdpr.6.5.4.zip</span>n’apaspuêtrevérifiéecaraucunesignaturen’aététrouvée.</p><p>unpack_package</p><p>Installationdeladernièreversion&#8230;</p><p>remove_old</p><p>process_success</p></div>"
}

Thanks in advance for your time and suggestions ❤️

Answer 1

✨ Explanation and Solution

Updating the plugin to prevent standard output couldn't be easier. No need to create a custom skin, WordPress already provides one for this case:

Automatic_Upgrader_Skin

Description: This skin is designed to be used when no output is intended, all output is captured and stored for the caller to process and log/email/discard.

After digging a lot I found that after every plugin update the next action is called 'upgrader_process_complete', array('Language_Pack_Upgrader', 'async_upgrade'). This action is called to update other parts such as the language packs.

This action create new instance of Language_Pack_Upgrader with a new custom Language_Pack_Upgrader_Skin which also generates data in the standard output.

But if the WP_Upgrader who call it use and Automatic_Upgrader_Skin the Language_Pack_Upgrader will reuse it.

We therefore only need the following few lines to prevent standard output during an update:

$skin = new Automatic_Upgrader_Skin();
$plugin_upgrader = new Plugin_Upgrader($skin);
$result = $plugin_upgrader->upgrade($name);

📍 Why ob_start and ob_get_clean doesn't work

Skins generated by the "upgrader_process_complete" action call the skin->feekback() method, which in turn calls show_message().

This contains the following lines, which broke my first implementation.

wp_ob_end_flush_all();
flush();