created Appcontroller to make it easiert to debug

build/controllers/AppController.php

+<?php
+/**
+ * @link http://www.yiiframework.com/
+ * @copyright Copyright (c) 2008 Yii Software LLC
+ * @license http://www.yiiframework.com/license/
+ */
+
+namespace yii\build\controllers;
+
+use Yii;
+use yii\base\InvalidParamException;
+use yii\console\Controller;
+use yii\helpers\Console;
+use yii\helpers\FileHelper;
+
+/**
+ * AppController will link the yii2 dev installation to the containted applications vendor dirs
+ * to help working on yii using the application to test it.
+ *
+ * @author Carsten Brandt <mail@cebe.cc>
+ * @since 2.0
+ */
+class AppController extends Controller
+{
+    public $defaultAction = 'link';
+
+    /**
+     * This command runs the following shell commands in the dev repo root:
+     *
+     * - Run `composer update`
+     * - `rm -rf apps/basic/vendor/yiisoft/yii2`
+     * - `rm -rf apps/basic/vendor/yiisoft/yii2-*`
+     *
+     * And replaces them with symbolic links to the extensions and framework path in the dev repo.
+     * @param string $app the application name `basic` or `advanced`.
+     */
+    public function actionLink($app)
+    {
+        // root of the dev repo
+        $base = dirname(dirname(__DIR__));
+        $appDir = "$base/apps/$app";
+
+        // cleanup
+        if (is_link($link = "$appDir/vendor/yiisoft/yii2")) {
+            $this->stdout("Removing symlink $link.\n");
+            unlink($link);
+        }
+        $extensions = $this->findDirs("$appDir/vendor/yiisoft");
+        foreach($extensions as $ext) {
+            if (is_link($link = "$appDir/vendor/yiisoft/yii2-$ext")) {
+                $this->stdout("Removing symlink $link.\n");
+                unlink($link);
+            }
+        }
+
+        // composer update
+        chdir($appDir);
+        passthru('composer update --prefer-dist');
+
+        // link directories
+        if (is_dir($link = "$appDir/vendor/yiisoft/yii2")) {
+            $this->stdout("Removing dir $link.\n");
+            FileHelper::removeDirectory($link);
+            $this->stdout("Creating symlink for $link.\n");
+            symlink("$base/framework", $link);
+        }
+        $extensions = $this->findDirs("$appDir/vendor/yiisoft");
+        foreach($extensions as $ext) {
+            if (is_dir($link = "$appDir/vendor/yiisoft/yii2-$ext")) {
+                $this->stdout("Removing dir $link.\n");
+                FileHelper::removeDirectory($link);
+                $this->stdout("Creating symlink for $link.\n");
+                symlink("$base/extensions/$ext", $link);
+            }
+        }
+
+        $this->stdout("done.\n");
+    }
+
+    protected function findDirs($dir)
+    {
+        $list = [];
+        $handle = @opendir($dir);
+        if ($handle === false) {
+            return [];
+        }
+        while (($file = readdir($handle)) !== false) {
+            if ($file === '.' || $file === '..') {
+                continue;
+            }
+            $path = $dir . DIRECTORY_SEPARATOR . $file;
+            if (is_dir($path) && preg_match('/^yii2-(.*)$/', $file, $matches)) {
+                $list[] = $matches[1];
+            }
+        }
+        closedir($handle);
+
+        foreach($list as $i => $e) {
+            if ($e == 'composer') { // skip composer to not break composer update
+                unset($list[$i]);
+            }
+        }
+
+        return $list;
+    }
+}