[WIP] Issue 1135 create project in existing directory

src/Composer/Downloader/VcsDownloader.php

@@ -55,7 +55,11 @@ public function download(PackageInterface $package, $path)
         }
 
         $this->io->write("  - Installing <info>" . $package->getName() . "</info> (<comment>" . VersionParser::formatVersion($package) . "</comment>)");
-        $this->filesystem->removeDirectory($path);
+
+        if (!$this->filesystem->directoryIsEmpty($path, array('composer.json'))) {
+            $this->filesystem->removeDirectory($path);
+        }
+
         $this->doDownload($package, $path);
         $this->io->write('');
     }
@@ -135,9 +139,10 @@ public function remove(PackageInterface $package, $path)
     /**
      * Prompt the user to check if changes should be stashed/removed or the operation aborted
      *
-     * @param  string            $path
-     * @param  bool              $stash if true (update) the changes can be stashed and reapplied after an update,
-     *                                  if false (remove) the changes should be assumed to be lost if the operation is not aborted
+     * @param string $path
+     * @param Boolean $update    if true (update) the changes can be stashed and reapplied after an update,
+     *                           if false (remove) the changes should be assumed to be lost if the operation is not aborted
+     *
      * @throws \RuntimeException in case the operation must be aborted
      */
     protected function cleanChanges($path, $update)

src/Composer/Installer/ProjectInstaller.php

@@ -15,6 +15,7 @@
 use Composer\Package\PackageInterface;
 use Composer\Downloader\DownloadManager;
 use Composer\Repository\InstalledRepositoryInterface;
+use Composer\Util\Filesystem;
 
 /**
  * Project Installer is used to install a single package into a directory as
@@ -58,13 +59,16 @@ public function isInstalled(InstalledRepositoryInterface $repo, PackageInterface
     public function install(InstalledRepositoryInterface $repo, PackageInterface $package)
     {
         $installPath = $this->installPath;
-        if (file_exists($installPath)) {
-            throw new \InvalidArgumentException("Project directory $installPath already exists.");
-        }
-        if (!file_exists(dirname($installPath))) {
-            throw new \InvalidArgumentException("Project root " . dirname($installPath) . " does not exist.");
+        $fs = new FileSystem();
+
+        if ($fs->directoryExists($installPath)) {
+            if (!$fs->directoryIsEmpty($installPath, array('composer.json'))) {
+                throw new \InvalidArgumentException("Project directory \"$installPath\" must be empty.");
+            }
+        } else {
+            mkdir($installPath, 0777, true);
         }
-        mkdir($installPath, 0777);
+
         $this->downloadManager->download($package, $installPath);
     }
 

src/Composer/Util/Filesystem.php

@@ -74,6 +74,33 @@ public function ensureDirectoryExists($directory)
         }
     }
 
+    public function directoryExists($dir)
+    {
+        return is_dir($dir);
+    }
+
+    /**
+     * @param string $dir
+     * @param array $excluding
+     * @return bool
+     * @throws \RuntimeException
+     */
+    public function directoryIsEmpty($dir, $excluding = array())
+    {
+        if (!$this->directoryExists($dir)) {
+            throw new \RuntimeException("Directory \"$dir\" does not exist");
+        }
+
+        $excludeList = array('.', '..');
+        if (!empty($excluding)) {
+           $excludeList = array_merge($excludeList, $excluding);
+        }
+
+        $dirContent = array_diff(scandir($dir), $excludeList);
+
+        return empty($dirContent);
+    }
+
     public function rename($source, $target)
     {
         if (true === @rename($source, $target)) {

tests/Composer/Test/Fixtures/projectTestDirectory/composer.json

@@ -0,0 +1,3 @@
+{
+    "name": "vendor/package-name-sample"
+}

tests/Composer/Test/Util/FilesystemTest.php

@@ -93,4 +93,37 @@ public function providePathCouples()
             array('C:/Temp', 'c:\Temp\test', "test"),
         );
     }
+
+    public function testDirectoryExists()
+    {
+        $fs = new Filesystem();
+        $directory1 = '/does/not/exist';
+        $directory2 = __DIR__;
+
+        $this->assertFalse($fs->directoryExists($directory1));
+        $this->assertTrue($fs->directoryExists($directory2));
+    }
+
+    /**
+     * @expectedException \RuntimeException
+     */
+    public function testDirectoryIsEmptyRuntimeException()
+    {
+        $fs = new Filesystem();
+        $dir = '/does/not/exist';
+
+        $fs->directoryIsEmpty($dir);
+    }
+
+    public function testDirectoryIsEmpty()
+    {
+        $fs = new Filesystem();
+        $dir = __DIR__;
+        $project = __DIR__.'/../Fixtures/projectTestDirectory';
+
+        $this->assertFalse($fs->directoryIsEmpty($dir));
+        $this->assertTrue($fs->directoryIsEmpty($project, array('composer.json')));
+        $this->assertFalse($fs->directoryIsEmpty($project));
+
+    }
 }