Client side error reporting for Minerva+MobileFrontend

This adds a client side error logger that will store errors
in EventLogging. We will use it to get a sense of the number
of errors inside mobile.

To enable make use of the new configuration variable
wgMinervaErrorLogSamplingRate = 1

Notes:
* the optional `meta` field will not be utilised by the generic
error handler.
* URI length is not trimmed for title. We will consider whether we need
to make any adjustments to the schema values during roll out.
** For stack trace, we limit the length by removing errorUrl (which is logged
separately)

Testing:
Add throw new Error('asasasa'); anywhere in your code and make
sure the code executes. It should trigger an Error event provided
that configuration has been updated.

Bug: T202026
Change-Id: I07f01b4c025b2e5e4cbf88ec05e7c536442c62cc

README.md

@@ -36,6 +36,17 @@ for the page.
 Controls whether site notices should be shown.
 See <https://www.mediawiki.org/wiki/Manual:$wgSiteNotice>.
 
+
+#### $wgMinervaErrorLogSamplingRate
+* Type: `Integer`
+* Default: `0`
+
+Whether to log client side errors to EventLogging. If 0, error logging is disabled.
+If 0.5, 50% of all client side errors will be logged to the EventLogging client.
+If 1, all errors will be logged to the EventLogging client, thus when enabling this
+care should be taken that your setup is bug free in order to not overwhelm the EventLogging
+server.
+
 #### $wgMinervaApplyKnownTemplateHacks
 
 * Type: `Boolean`

includes/MinervaHooks.php

@@ -190,7 +190,11 @@ class MinervaHooks {
 	 * @return bool
 	 */
 	public static function onResourceLoaderGetConfigVars( &$vars ) {
+		$config = MediaWikiServices::getInstance()->getConfigFactory()
+			->makeConfig( 'minerva' );
+
 		$vars += [
+			'wgMinervaErrorLogSamplingRate' => $config->get( 'MinervaErrorLogSamplingRate' ),
 			'wgMinervaReadOnly' => wfReadOnly()
 		];
 

resources/skins.minerva.scripts/errorLogging.js

@@ -0,0 +1,59 @@
+( function ( M, requestIdleCallback, track, config, trackSubscribe, user, experiments ) {
+	requestIdleCallback( function () {
+		/**
+		 * Handle an error and log it if necessary
+		 * @param {string} errorMessage to be logged
+		 * @param {number} [lineNumber] of error
+		 * @param {number} [columnNumber] of error
+		 * @param {string} [errorUrl] to be logged
+		 */
+		function handleError( errorMessage, lineNumber, columnNumber, errorUrl ) {
+			var errorSamplingRate = config.get( 'wgMinervaErrorLogSamplingRate', 0 ),
+				sessionToken = user.sessionId(),
+				EVENT_CLIENT_ERROR_LOG = 'wikimedia.event.WebClientError',
+				page = M.getCurrentPage(),
+				util = M.require( 'mobile.startup/util' ),
+				errorExperiment = {
+					name: 'WebClientError',
+					enabled: errorSamplingRate > 0,
+					buckets: {
+						on: errorSamplingRate,
+						off: 1 - errorSamplingRate
+					}
+				},
+				isErrorLoggingEnabled = experiments.getBucket( errorExperiment, sessionToken ) === 'on',
+				DEFAULT_ERROR_DATA = {
+					sessionToken: sessionToken,
+					skin: config.get( 'skin' ),
+					wgVersion: config.get( 'wgVersion' ),
+					mobileMode: config.get( 'wgMFMode', 'desktop' ),
+					isAnon: user.isAnon(),
+					revision: page.getRevisionId()
+				};
+
+			if ( isErrorLoggingEnabled ) {
+				track( EVENT_CLIENT_ERROR_LOG,
+					util.extend( {
+						userUrl: window.location.href,
+						errorUrl: errorUrl,
+						errorMessage: errorMessage,
+						// Due to concerns for the length of the stack trace and going over the limit for URI length
+						// this is currently set to empty string.
+						errorStackTrace: '',
+						errorLineNumber: lineNumber || 0,
+						errorColumnNumber: columnNumber || 0
+					}, DEFAULT_ERROR_DATA )
+				);
+			}
+		}
+		// track RL exceptions
+		trackSubscribe( 'resourceloader.exception', function ( topic, data ) {
+			var err = data.exception;
+			handleError( err.message, err.lineNumber, err.columnNumber );
+		} );
+		// setup the global error handler
+		trackSubscribe( 'global.error', function ( topic, error ) {
+			handleError( error.errorMessage, error.lineNumber, error.columnNumber, error.url );
+		} );
+	} );
+}( mw.mobileFrontend, mw.requestIdleCallback, mw.track, mw.config, mw.trackSubscribe, mw.user, mw.experiments ) );

skin.json

@@ -22,6 +22,7 @@
 		}
 	},
 	"config": {
+		"MinervaErrorLogSamplingRate": 0,
 		"MinervaDownloadNamespaces": [ 0 ],
 		"MinervaEnableSiteNotice": false,
 		"MinervaCustomLogos": [],
@@ -152,7 +153,8 @@
 		}
 	},
 	"EventLoggingSchemas": {
-		"PageIssues": 18326688
+		"PageIssues": 18326688,
+		"WebClientError": 18340282
 	},
 	"ResourceModules": {
 		"skins.minerva.base.reset": {
@@ -430,6 +432,7 @@
 				"resources/skins.minerva.scripts/PageIssuesOverlay.js",
 				"resources/skins.minerva.scripts/pageIssues.js",
 				"resources/skins.minerva.scripts/init.js",
+				"resources/skins.minerva.scripts/errorLogging.js",
 				"resources/skins.minerva.scripts/initLogging.js",
 				"resources/skins.minerva.scripts/mobileRedirect.js",
 				"resources/skins.minerva.scripts/search.js",