Report uncaught errors via mw.track

Adds a global error handler that sends errors to mw.track as
an errorLogging.windowOnerror event.

Bug: T88874
Change-Id: Ic091c9f93c59bda47bda2cfd609c64cd1d014b39

.jshintrc

@@ -22,6 +22,7 @@
 		"mediaWiki": true,
 		"JSON": true,
 		"jQuery": false,
-		"QUnit": false
+		"QUnit": false,
+		"sinon": false
 	}
 }

maintenance/jsduck/categories.json

@@ -14,7 +14,8 @@
 					"mw.html.Cdata",
 					"mw.html.Raw",
 					"mw.hook",
-					"mw.template"
+					"mw.template",
+					"mw.errorLogger"
 				]
 			},
 			{

maintenance/jsduck/eg-iframe.html

@@ -41,6 +41,7 @@
 	</script>
 	<script src="modules/lib/jquery/jquery.js"></script>
 	<script src="modules/src/mediawiki/mediawiki.js"></script>
+	<script src="modules/src/mediawiki/mediawiki.errorLogger.js"></script>
 	<script src="modules/src/mediawiki/mediawiki.startUp.js"></script>
 	<style>
 		.mw-jsduck-log {

resources/Resources.php

@@ -775,6 +775,7 @@ return array(
 		// Keep maintenance/jsduck/eg-iframe.html in sync
 		'scripts' => array(
 			'resources/src/mediawiki/mediawiki.js',
+			'resources/src/mediawiki/mediawiki.errorLogger.js',
 			'resources/src/mediawiki/mediawiki.startUp.js',
 		),
 		'debugScripts' => 'resources/src/mediawiki/mediawiki.log.js',

resources/src/mediawiki/mediawiki.errorLogger.js

@@ -0,0 +1,49 @@
+/**
+ * Try to catch errors in modules which don't do their own error handling.
+ * @class mw.errorLogger
+ * @singleton
+ */
+( function ( mw ) {
+	'use strict';
+
+	mw.errorLogger = {
+		/**
+		 * Fired via mw.track when an error is not handled by local code and is caught by the
+		 * window.onerror handler.
+		 *
+		 * @event global_error
+		 * @param {string} errorMessage Error errorMessage.
+		 * @param {string} url URL where error was raised.
+		 * @param {number} lineNumber Line number where error was raised.
+		 * @param {number} [columnNumber] Line number where error was raised. Not all browsers
+		 *   support this.
+		 * @param {Error|Mixed} [errorObject] The error object. Typically an instance of Error, but anything
+		 *   (even a primitive value) passed to a throw clause will end up here.
+		 */
+
+		/**
+		 * Install a window.onerror handler that will report via mw.track, while preserving
+		 * any previous handler.
+		 * @param {Object} window
+		 */
+		installGlobalHandler: function ( window ) {
+			// We will preserve the return value of the previous handler. window.onerror works the
+			// opposite way than normal event handlers (returning true will prevent the default
+			// action, returning false will let the browser handle the error normally, by e.g.
+			// logging to the console), so our fallback old handler needs to return false.
+			var oldHandler = window.onerror || function () { return false; };
+
+			/**
+			 * Dumb window.onerror handler which forwards the errors via mw.track.
+			 * @fires global_error
+			 */
+			window.onerror = function ( errorMessage, url, lineNumber, columnNumber, errorObject ) {
+				mw.track( 'global.error', { errorMessage: errorMessage, url: url,
+					lineNumber: lineNumber, columnNumber: columnNumber, errorObject: errorObject } );
+				return oldHandler.apply( this, arguments );
+			};
+		}
+	};
+
+	mw.errorLogger.installGlobalHandler( window );
+}( mediaWiki ) );

tests/qunit/QUnitTestResources.php

@@ -62,6 +62,7 @@ return array(
 			'tests/qunit/suites/resources/jquery/jquery.tablesorter.parsers.test.js',
 			'tests/qunit/suites/resources/jquery/jquery.textSelection.test.js',
 			'tests/qunit/data/mediawiki.jqueryMsg.data.js',
+			'tests/qunit/suites/resources/mediawiki/mediawiki.errorLogger.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.jqueryMsg.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.jscompat.test.js',
 			'tests/qunit/suites/resources/mediawiki/mediawiki.test.js',

tests/qunit/suites/resources/mediawiki/mediawiki.errorLogger.test.js

@@ -0,0 +1,42 @@
+( function ( $, mw ) {
+	QUnit.module( 'mediawiki.errorLogger', QUnit.newMwEnvironment() );
+
+	QUnit.test( 'installGlobalHandler', 7, function ( assert ) {
+		var w = {},
+			errorMessage = 'Foo',
+			errorUrl = 'http://example.com',
+			errorLine = '123',
+			errorColumn = '45',
+			errorObject = new Error( 'Foo'),
+			oldHandler = this.sandbox.stub();
+
+		this.sandbox.stub( mw, 'track' );
+
+		mw.errorLogger.installGlobalHandler( w );
+
+		assert.ok( w.onerror, 'Global handler has been installed' );
+		assert.strictEqual( w.onerror( errorMessage, errorUrl, errorLine ), false,
+			'Global handler returns false when there is no previous handler' );
+		sinon.assert.calledWithExactly( mw.track, 'global.error',
+			sinon.match( { errorMessage: errorMessage, url: errorUrl, lineNumber: errorLine } ) );
+
+		mw.track.reset();
+		w.onerror( errorMessage, errorUrl, errorLine, errorColumn, errorObject );
+		sinon.assert.calledWithExactly( mw.track, 'global.error',
+			sinon.match( { errorMessage: errorMessage, url: errorUrl, lineNumber: errorLine,
+			columnNumber: errorColumn, errorObject: errorObject } ) );
+
+		w = { onerror: oldHandler };
+
+		mw.errorLogger.installGlobalHandler( w );
+		w.onerror( errorMessage, errorUrl, errorLine );
+		sinon.assert.calledWithExactly( oldHandler, errorMessage, errorUrl, errorLine );
+
+		oldHandler.returns( false );
+		assert.strictEqual( w.onerror( errorMessage, errorUrl, errorLine ), false,
+			'Global handler preserves false return from previous handler' );
+		oldHandler.returns( true );
+		assert.strictEqual( w.onerror( errorMessage, errorUrl, errorLine ), true,
+			'Global handler preserves true return from previous handler' );
+	} );
+}( jQuery, mediaWiki ) );