Add PSR-4 autoload paths for app plugins.

This change avoids having to update the app's composer.json to add
autoload paths for app plugins under the "plugins" folder.

Author: ADmad

src/Plugin.php

@@ -42,9 +42,55 @@ public static function getSubscribedEvents()
     {
         return [
             'post-autoload-dump' => 'postAutoloadDump',
+            'pre-autoload-dump' => 'preAutoloadDump',
         ];
     }
 
+    /**
+     * Add PSR-4 autoload paths for app plugins.
+     *
+     * @param \Composer\Script\Event $event
+     * @return void
+     */
+    public function preAutoloadDump(Event $event): void
+    {
+        $package = $event->getComposer()->getPackage();
+        $autoload = $package->getAutoload();
+        $devAutoload = $package->getDevAutoload();
+
+        $extra = $package->getExtra();
+        if (empty($extra['plugin-paths'])) {
+            $extra['plugin-paths'] = ['plugins'];
+        }
+
+        $root = dirname(realpath($event->getComposer()->getConfig()->get('vendor-dir')));
+        foreach ($extra['plugin-paths'] as $pluginsPath) {
+            foreach (new DirectoryIterator($root . '/' . $pluginsPath) as $fileInfo) {
+                if (!$fileInfo->isDir() || $fileInfo->isDot()) {
+                    continue;
+                }
+
+                $folderName = $fileInfo->getFilename();
+                if ($folderName[0] === '.') {
+                    continue;
+                }
+
+                $pluginNamespace = $folderName . '\\';
+                $pluginTestNamespace = $folderName . '\\Test\\';
+                $path = $pluginsPath . '/' . $folderName . '/';
+                if (!isset($autoload['psr-4'][$pluginNamespace])) {
+                    $autoload['psr-4'][$pluginNamespace] = $path . 'src';
+                }
+                if (!isset($devAutoload['psr-4'][$pluginTestNamespace])) {
+                    $devAutoload['psr-4'][$pluginTestNamespace] = $path . 'tests';
+                }
+            }
+        }
+
+        $package->setAutoload($autoload);
+        $package->setDevAutoload($devAutoload);
+    }
+
     /**
      * Called whenever composer (re)generates the autoloader.
      *

tests/TestCase/PluginTest.php

@@ -8,7 +8,9 @@
 use Composer\Config;
 use Composer\IO\IOInterface;
 use Composer\Package\Package;
+use Composer\Package\RootPackage;
 use Composer\Repository\RepositoryManager;
+use Composer\Script\Event;
 use Composer\Util\HttpDownloader;
 use PHPUnit\Framework\TestCase;
 
@@ -67,7 +69,9 @@ public function setUp(): void
         $this->composer = new Composer();
         $config = new Config();
         $config->merge([
-            'vendor-dir' => $this->path . '/vendor',
+            'config' => [
+                'vendor-dir' => $this->path . '/vendor',
+            ],
         ]);
 
         $this->composer->setConfig($config);
@@ -109,6 +113,7 @@ public function testGetSubscribedEvents()
     {
         $expected = [
             'post-autoload-dump' => 'postAutoloadDump',
+            'pre-autoload-dump' => 'preAutoloadDump',
         ];
 
         $this->assertSame($expected, $this->plugin->getSubscribedEvents());
@@ -120,6 +125,54 @@ public function testGetConfigFilePath()
         $this->assertFileExists(dirname($path));
     }
 
+    public function testPreAutoloadDump()
+    {
+        $package = new RootPackage('App', '1.0.0', '1.0.0');
+        $package->setExtra([
+            'plugin-paths' => [
+                'app_plugins',
+                'plugins',
+            ],
+        ]);
+        $package->setAutoload([
+            'psr-4' => [
+                'Foo\\' => 'xyz/Foo/src',
+            ],
+        ]);
+        $package->setDevAutoload([
+            'psr-4' => [
+                'Foo\Test\\' => 'xyz/Foo/tests',
+            ],
+        ]);
+        $this->composer->setPackage($package);
+
+        $event = new Event('', $this->composer, $this->io);
+
+        $this->plugin->preAutoloadDump($event);
+
+        $expected = [
+            'psr-4' => [
+                'Foo\\' => 'xyz/Foo/src',
+                'Fee\\' => 'plugins/Fee/src',
+                'Fum\\' => 'plugins/Fum/src',
+                'Foe\\' => 'plugins/Foe/src',
+                'Bar\\' => 'app_plugins/Bar/src',
+            ],
+        ];
+        $this->assertEquals($expected, $package->getAutoload());
+
+        $expected = [
+            'psr-4' => [
+                'Foo\Test\\' => 'xyz/Foo/tests',
+                'Fee\Test\\' => 'plugins/Fee/tests',
+                'Fum\Test\\' => 'plugins/Fum/tests',
+                'Foe\Test\\' => 'plugins/Foe/tests',
+                'Bar\Test\\' => 'app_plugins/Bar/tests',
+            ],
+        ];
+        $this->assertEquals($expected, $package->getDevAutoload());
+    }
+
     public function testGetPrimaryNamespace()
     {
         $autoload = [