Disable app that bricks the server after enabling

If an app is getting enabled in the web UI, an ajax call is now made to
make sure the server still works. If it doesn't, it sends an emergency
app disabling call to disable the breaking app.

lib/base.php

@@ -823,12 +823,28 @@ class OC {
 			exit();
 		}
 
-		$request = \OC::$server->getRequest()->getPathInfo();
+		$request = \OC::$server->getRequest();
-		if (substr($request, -3) !== '.js') { // we need these files during the upgrade
+		$requestPath = $request->getPathInfo();
+		if (substr($requestPath, -3) !== '.js') { // we need these files during the upgrade
 			self::checkMaintenanceMode();
 			self::checkUpgrade();
 		}
 
+		// emergency app disabling
+		if ($requestPath === '/disableapp'
+			&& $request->getMethod() === 'POST'
+			&& ((string)$request->getParam('appid')) !== ''
+		) {
+			\OCP\JSON::callCheck();
+			\OCP\JSON::checkAdminUser();
+			$appId = (string)$request->getParam('appid');
+			$appId = \OC_App::cleanAppId($appId);
+
+			\OC_App::disable($appId);
+			\OC_JSON::success();
+			exit();
+		}
+
 		// Always load authentication apps
 		OC_App::loadApps(['authentication']);
 

settings/js/apps.js

@@ -212,7 +212,19 @@ OC.Settings.Apps = OC.Settings.Apps || {
 		return app.types && app.types.indexOf(type) !== -1;
 	},
 
+	/**
+	 * Checks the server health.
+	 *
+	 * If the promise fails, the server is broken.
+	 *
+	 * @return {Promise} promise
+	 */
+	_checkServerHealth: function() {
+		return $.get(OC.generateUrl('apps/files'));
+	},
+
 	enableApp:function(appId, active, element, groups) {
+		var self = this;
 		OC.Settings.Apps.hideErrorMessage(appId);
 		groups = groups || [];
 		var appItem = $('div#app-'+appId+'');
@@ -242,6 +254,8 @@ OC.Settings.Apps = OC.Settings.Apps || {
 				}
 			},'json');
 		} else {
+			// TODO: display message to admin to not refresh the page!
+			// TODO: lock UI to prevent further operations
 			$.post(OC.filePath('settings','ajax','enableapp.php'),{appid: appId, groups: groups},function(result) {
 				if(!result || result.status !== 'success') {
 					if (result.data && result.data.message) {
@@ -254,6 +268,7 @@ OC.Settings.Apps = OC.Settings.Apps || {
 					element.val(t('settings','Enable'));
 					appItem.addClass('appwarning');
 				} else {
+					self._checkServerHealth().done(function() {
 						if (result.data.update_required) {
 							OC.Settings.Apps.showReloadMessage();
 
@@ -283,6 +298,25 @@ OC.Settings.Apps = OC.Settings.Apps || {
 								appItem.data('groups', '');
 							}
 						}
+					}).fail(function() {
+						// server borked, emergency disable app
+						$.post(OC.webroot + '/index.php/disableapp', {appid: appId}, function() {
+							OC.Settings.Apps.showErrorMessage(
+								appId,
+								t('settings', 'Error: this app cannot be enabled because it makes the server unstable')
+							);
+							appItem.data('errormsg', t('settings', 'Error while enabling app'));
+							element.val(t('settings','Enable'));
+							appItem.addClass('appwarning');
+						}).fail(function() {
+							OC.Settings.Apps.showErrorMessage(
+								appId,
+								t('settings', 'Error: could not disable broken app')
+							);
+							appItem.data('errormsg', t('settings', 'Error while disabling broken app'));
+							element.val(t('settings','Enable'));
+						});
+					});
 				}
 			},'json')
 				.fail(function() {