Only intercept exceptions of type "NotFoundException" instead of any Exception

The sharing backend may throw another exception for example when the activity app encounters a problem. Previously this just triggered a 404 error page and the exception got not logged at all. With this change such exceptions get not intercepted and regularly handled as exceptions so that we have meaningful log data. Also the user will be shown a window informing him that an error happened.

Helps to debug cases such as https://github.com/owncloud/core/issues/19465

apps/files_sharing/lib/controllers/sharecontroller.php

 use OCP\User;
 use OCP\Util;
 use OCA\Files_Sharing\Activity;
+use \OCP\Files\NotFoundException;
 
 /**
  * Class ShareController
 	 * @param string $token
 	 * @param string $path
 	 * @return TemplateResponse|RedirectResponse
+	 * @throws NotFoundException
 	 */
 	public function showShare($token, $path = '') {
 		\OC_User::setIncognitoMode(true);
 			$getPath = Filesystem::normalizePath($path);
 			$originalSharePath .= $path;
 		} else {
-			throw new OCP\Files\NotFoundException();
+			throw new NotFoundException();
 		}
 
 		$file = basename($originalSharePath);
 	/**
 	 * @param string $token
 	 * @return string Resolved file path of the token
-	 * @throws \Exception In case share could not get properly resolved
+	 * @throws NotFoundException In case share could not get properly resolved
 	 */
 	private function getPath($token) {
 		$linkItem = Share::getShareByToken($token, false);
 			$rootLinkItem = Share::resolveReShare($linkItem);
 			if (isset($rootLinkItem['uid_owner'])) {
 				if(!$this->userManager->userExists($rootLinkItem['uid_owner'])) {
-					throw new \Exception('Owner of the share does not exist anymore');
+					throw new NotFoundException('Owner of the share does not exist anymore');
 				}
 				OC_Util::tearDownFS();
 				OC_Util::setupFS($rootLinkItem['uid_owner']);
 			}
 		}
 
-		throw new \Exception('No file found belonging to file.');
+		throw new NotFoundException('No file found belonging to file.');
 	}
 }

apps/files_sharing/lib/middleware/sharingcheckmiddleware.php

 use OCP\AppFramework\Http\NotFoundResponse;
 use OCP\AppFramework\Middleware;
 use OCP\AppFramework\Http\TemplateResponse;
+use OCP\Files\NotFoundException;
 use OCP\IConfig;
 
 /**
 
 	/**
 	 * Check if sharing is enabled before the controllers is executed
+	 *
+	 * @param \OCP\AppFramework\Controller $controller
+	 * @param string $methodName
+	 * @throws NotFoundException
 	 */
 	public function beforeController($controller, $methodName) {
 		if(!$this->isSharingEnabled()) {
-			throw new \Exception('Sharing is disabled.');
+			throw new NotFoundException('Sharing is disabled.');
 		}
 	}
 
 	/**
-	 * Return 404 page in case of an exception
+	 * Return 404 page in case of a not found exception
+	 *
 	 * @param \OCP\AppFramework\Controller $controller
 	 * @param string $methodName
 	 * @param \Exception $exception
-	 * @return TemplateResponse
+	 * @return NotFoundResponse
+	 * @throws \Exception
 	 */
-	public function afterException($controller, $methodName, \Exception $exception){
-		return new NotFoundResponse();
+	public function afterException($controller, $methodName, \Exception $exception) {
+		if(is_a($exception, '\OCP\Files\NotFoundException')) {
+			return new NotFoundResponse();
+		}
+
+		throw $exception;
 	}
 
 	/**

apps/files_sharing/tests/middleware/sharingcheckmiddleware.php

  */
 
 namespace OCA\Files_Sharing\Middleware;
-
+use OCP\AppFramework\Http\NotFoundResponse;
+use OCP\Files\NotFoundException;
 
 /**
  * @package OCA\Files_Sharing\Middleware\SharingCheckMiddleware
 	private $appManager;
 	/** @var SharingCheckMiddleware */
 	private $sharingCheckMiddleware;
+	/** @var \OCP\AppFramework\Controller */
+	private $controllerMock;
 
 	protected function setUp() {
 		$this->config = $this->getMockBuilder('\OCP\IConfig')
 			->disableOriginalConstructor()->getMock();
 		$this->appManager = $this->getMockBuilder('\OCP\App\IAppManager')
 			->disableOriginalConstructor()->getMock();
+		$this->controllerMock = $this->getMockBuilder('\OCP\AppFramework\Controller')
+			->disableOriginalConstructor()->getMock();
 
 		$this->sharingCheckMiddleware = new SharingCheckMiddleware('files_sharing', $this->config, $this->appManager);
 	}
 		$this->assertFalse(self::invokePrivate($this->sharingCheckMiddleware, 'isSharingEnabled'));
 	}
 
+	public function testBeforeControllerWithSharingEnabled() {
+		$this->appManager
+			->expects($this->once())
+			->method('isEnabledForUser')
+			->with('files_sharing')
+			->will($this->returnValue(true));
+
+		$this->config
+			->expects($this->at(0))
+			->method('getAppValue')
+			->with('core', 'shareapi_enabled', 'yes')
+			->will($this->returnValue('yes'));
+
+		$this->config
+			->expects($this->at(1))
+			->method('getAppValue')
+			->with('core', 'shareapi_allow_links', 'yes')
+			->will($this->returnValue('yes'));
+
+		$this->sharingCheckMiddleware->beforeController($this->controllerMock, 'myMethod');
+	}
+
+	/**
+	 * @expectedException \OCP\Files\NotFoundException
+	 * @expectedExceptionMessage Sharing is disabled.
+	 */
+	public function testBeforeControllerWithSharingDisabled() {
+		$this->appManager
+			->expects($this->once())
+			->method('isEnabledForUser')
+			->with('files_sharing')
+			->will($this->returnValue(false));
+
+		$this->sharingCheckMiddleware->beforeController($this->controllerMock, 'myMethod');
+	}
+
+	/**
+	 * @expectedException \Exception
+	 * @expectedExceptionMessage My Exception message
+	 */
+	public function testAfterExceptionWithRegularException() {
+		$this->sharingCheckMiddleware->afterException($this->controllerMock, 'myMethod', new \Exception('My Exception message'));
+	}
+
+	public function testAfterExceptionWithNotFoundException() {
+		$this->assertEquals(new NotFoundResponse(), $this->sharingCheckMiddleware->afterException($this->controllerMock, 'myMethod', new NotFoundException('My Exception message')));
+	}
+
 }