Copy Etag header to OC-Etag for sabre calls

apps/files/appinfo/remote.php

@@ -65,6 +65,7 @@ $server->on('beforeMethod', function () use ($server, $objectTree) {
 			)
 		)
 	);
+	$server->addPlugin(new \OC\Connector\Sabre\CopyEtagHeaderPlugin());
 }, 30); // priority 30: after auth (10) and acl(20), before lock(50) and handling the request
 
 // And off we go!

lib/private/connector/sabre/copyetagheaderplugin.php

@@ -0,0 +1,46 @@
+<?php
+
+/**
+ * ownCloud
+ *
+ * @author Vincent Petry
+ * @copyright 2015 Vincent Petry <pvince81@owncloud.com>
+ *
+ * @license AGPL3
+ */
+
+namespace OC\Connector\Sabre;
+
+use \Sabre\HTTP\RequestInterface;
+use \Sabre\HTTP\ResponseInterface;
+
+/**
+ * Copies the "Etag" header to "OC-Etag" after any request.
+ * This is a workaround for setups that automatically strip
+ * or mangle Etag headers.
+ */
+class CopyEtagHeaderPlugin extends \Sabre\DAV\ServerPlugin {
+	/**
+	 * This initializes the plugin.
+	 *
+	 * @param \Sabre\DAV\Server $server Sabre server
+	 *
+	 * @return void
+	 */
+	public function initialize(\Sabre\DAV\Server $server) {
+		$server->on('afterMethod', array($this, 'afterMethod'));
+	}
+
+	/**
+	 * After method, copy the "Etag" header to "OC-Etag" header.
+	 *
+	 * @param RequestInterface $request request
+	 * @param ResponseInterface $response response
+	 */
+	public function afterMethod(RequestInterface $request, ResponseInterface $response) {
+		$eTag = $response->getHeader('Etag');
+		if (!empty($eTag)) {
+			$response->setHeader('OC-ETag', $eTag);
+		}
+	}
+}

tests/lib/connector/sabre/copyetagheaderplugintest.php

@@ -0,0 +1,43 @@
+<?php
+
+namespace Tests\Connector\Sabre;
+
+/**
+ * Copyright (c) 2015 Vincent Petry <pvince81@owncloud.com>
+ * This file is licensed under the Affero General Public License version 3 or
+ * later.
+ * See the COPYING-README file.
+ */
+class CopyEtagPluginTest extends \Test\TestCase {
+
+	/**
+	 * @var \OC\Connector\Sabre\CopyEtagHeaderPlugin
+	 */
+	private $plugin;
+
+	public function setUp() {
+		parent::setUp();
+		$this->server = new \Sabre\DAV\Server();
+		$this->plugin = new \OC\Connector\Sabre\CopyEtagHeaderPlugin($this->tree);
+		$this->plugin->initialize($this->server);
+	}
+
+	public function testCopyEtag() {
+		$request = new \Sabre\Http\Request();
+		$response = new \Sabre\Http\Response();
+		$response->setHeader('Etag', 'abcd');
+
+		$this->plugin->afterMethod($request, $response);
+
+		$this->assertEquals('abcd', $response->getHeader('OC-Etag'));
+	}
+
+	public function testNoopWhenEmpty() {
+		$request = new \Sabre\Http\Request();
+		$response = new \Sabre\Http\Response();
+
+		$this->plugin->afterMethod($request, $response);
+
+		$this->assertNull($response->getHeader('OC-Etag'));
+	}
+}