1 files changed, 49 insertions, 0 deletions
diff --git a/resources/src/mediawiki/mediawiki.errorLogger.js b/resources/src/mediawiki/mediawiki.errorLogger.js
new file mode 100644
index 00000000..9f4f19dd
--- /dev/null
+++ b/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 ) );