Revert "Avoid loading plugins that do not match the current plugin api even during installation"

This reverts commit 21f5933e01.

Commit 21f5933e breaks fresh installations of cakephp applications, or
any project where a dependency uses a different composer plugin
installer than the upstream project.

Closes auraphp/Aura.Intl#20

src/Composer/Plugin/PluginManager.php

@@ -106,26 +106,6 @@ class PluginManager
             return;
         }
 
-        $requiresComposer = null;
-        foreach ($package->getRequires() as $link) { /** @var Link $link */
-            if ('composer-plugin-api' === $link->getTarget()) {
-                $requiresComposer = $link->getConstraint();
-                break;
-            }
-        }
-
-        if (!$requiresComposer) {
-            throw new \RuntimeException("Plugin ".$package->getName()." is missing a require statement for a version of the composer-plugin-api package.");
-        }
-
-        $currentPluginApiVersion = $this->getPluginApiVersion();
-        $currentPluginApiConstraint = new Constraint('==', $this->versionParser->normalize($currentPluginApiVersion));
-
-        if (!$requiresComposer->matches($currentPluginApiConstraint)) {
-            $this->io->writeError('<warning>The "' . $package->getName() . '" plugin was skipped because it requires a Plugin API version ("' . $requiresComposer->getPrettyString() . '") that does not match your Composer installation ("' . $currentPluginApiVersion . '"). You may need to run composer update with the "--no-plugins" option.</warning>');
-            return;
-        }
-
         $oldInstallerPlugin = ($package->getType() === 'composer-installer');
 
         if (in_array($package->getName(), $this->registeredPlugins)) {
@@ -229,7 +209,28 @@ class PluginManager
                 continue;
             }
             if ('composer-plugin' === $package->getType()) {
+                $requiresComposer = null;
+                foreach ($package->getRequires() as $link) { /** @var Link $link */
+                    if ('composer-plugin-api' === $link->getTarget()) {
+                        $requiresComposer = $link->getConstraint();
+                        break;
+                    }
+                }
+
+                if (!$requiresComposer) {
+                    throw new \RuntimeException("Plugin ".$package->getName()." is missing a require statement for a version of the composer-plugin-api package.");
+                }
+
+                $currentPluginApiVersion = $this->getPluginApiVersion();
+                $currentPluginApiConstraint = new Constraint('==', $this->versionParser->normalize($currentPluginApiVersion));
+
+                if (!$requiresComposer->matches($currentPluginApiConstraint)) {
+                    $this->io->writeError('<warning>The "' . $package->getName() . '" plugin was skipped because it requires a Plugin API version ("' . $requiresComposer->getPrettyString() . '") that does not match your Composer installation ("' . $currentPluginApiVersion . '"). You may need to run composer update with the "--no-plugins" option.</warning>');
+                    continue;
+                }
+
                 $this->registerPackage($package);
+
             // Backward compatibility
             } elseif ('composer-installer' === $package->getType()) {
                 $this->registerPackage($package);