Add extra.plugin-optional to auto-disable plugins in non-interactive mode (#11316)

doc/articles/plugins.md

@@ -332,6 +332,20 @@ in your composer.json to hint to Composer that the plugin should be activated as
 as possible to prevent any bad side-effects from Composer assuming packages are installed
 in another location than they actually are.
 
+### plugin-optional
+
+Because Composer plugins can be used to perform actions which are necessary for installing
+a working application, like modifying which path files get stored in, skipping required
+plugins unintentionally can result in broken applications. So, in non-interactive mode,
+Composer will fail if a new plugin is not listed in ["allow-plugins"](../06-config.md#allow-plugins)
+to force users to decide if they want to execute the plugin, to avoid silent failures.
+
+As of Composer 2.5.3, you can use the setting `{"extra": {"plugin-optional": true}}` on
+your plugin, to tell Composer that skipping the plugin has no catastrophic consequences,
+and it can safely be disabled in non-interactive mode if it is not yet listed in
+"allow-plugins". The next interactive run of Composer will still prompt users to choose if
+they want to enable or disable the plugin.
+
 ## Plugin Autoloading
 
 Due to plugins being loaded by Composer at runtime, and to ensure that plugins which

src/Composer/Plugin/PluginManager.php

@@ -198,7 +198,8 @@ class PluginManager
             }
         }
 
-        if (!$this->isPluginAllowed($package->getName(), $isGlobalPlugin)) {
+        $extra = $package->getExtra();
+        if (!$this->isPluginAllowed($package->getName(), $isGlobalPlugin, isset($extra['plugin-optional']) && true === $extra['plugin-optional'])) {
             $this->io->writeError('Skipped loading "'.$package->getName() . '" '.($isGlobalPlugin ? '(installed globally) ' : '').'as it is not in config.allow-plugins', true, IOInterface::DEBUG);
 
             return;
@@ -394,10 +395,13 @@ class PluginManager
 
         if ($sourcePackage === null) {
             trigger_error('Calling PluginManager::addPlugin without $sourcePackage is deprecated, if you are using this please get in touch with us to explain the use case', E_USER_DEPRECATED);
-        } elseif (!$this->isPluginAllowed($sourcePackage->getName(), $isGlobalPlugin)) {
+        } else {
+            $extra = $sourcePackage->getExtra();
+            if (!$this->isPluginAllowed($sourcePackage->getName(), $isGlobalPlugin, isset($extra['plugin-optional']) && true === $extra['plugin-optional'])) {
                 $this->io->writeError('Skipped loading "'.get_class($plugin).' from '.$sourcePackage->getName() . '" '.($isGlobalPlugin ? '(installed globally) ' : '').' as it is not in config.allow-plugins', true, IOInterface::DEBUG);
                 return;
             }
+        }
 
         $details = array();
         if ($sourcePackage) {
@@ -693,9 +697,10 @@ class PluginManager
      *
      * @param string $package
      * @param bool $isGlobalPlugin
+     * @param bool $optional
      * @return bool
      */
-    public function isPluginAllowed($package, $isGlobalPlugin)
+    public function isPluginAllowed($package, $isGlobalPlugin, $optional = false)
     {
         if ($isGlobalPlugin) {
             $rules = &$this->allowGlobalPluginRules;
@@ -763,6 +768,8 @@ class PluginManager
                         break;
                 }
             }
+        } elseif ($optional) {
+            return false;
         }
 
         throw new PluginBlockedException(