Prepare ULS for EventLogging

This change introduces a new configuration variable, $wgULSEventLogging. When
set to true, ULS will register an EventLogging schema module for
<http://meta.wikimedia.org/wiki/Schema:UniversalLanguageSelector>,
making it possible to log events using `mw.uls.logEvent`. When false, the
schema module is not loaded, and `mw.uls.logEvent` is a no-op.

Change-Id: I7139e67cc2f830a6b4b3c8ff1fc72dfcdec9a699

UniversalLanguageSelector.php

@@ -116,6 +116,13 @@ $wgULSIMEEnabled = true;
  */
 $wgULSPosition = 'personal';
 
+/**
+ * Whether to use EventLogging. The EventLogging extension must be installed
+ * if this option is enabled.
+ * @since 2013.06
+ */
+$wgULSEventLogging = false;
+
 $dir = __DIR__;
 
 // Internationalization
@@ -139,11 +146,12 @@ $wgHooks['UserGetLanguageObject'][] = 'UniversalLanguageSelectorHooks::getLangua
 $wgHooks['SkinTemplateOutputPageBeforeExec'][] =
 	'UniversalLanguageSelectorHooks::onSkinTemplateOutputPageBeforeExec';
 
+
 $wgDefaultUserOptions['uls-preferences'] = '';
 $wgHooks['GetPreferences'][] = 'UniversalLanguageSelectorHooks::onGetPreferences';
 
 $wgExtensionFunctions[] = function() {
-	global $wgHooks, $wgULSGeoService;
+	global $wgHooks, $wgResourceModules, $wgULSEventLogging, $wgULSGeoService;
 
 	if ( $wgULSGeoService === true ) {
 		$wgHooks['BeforePageDisplay'][] = function( &$out ) {
@@ -153,6 +161,24 @@ $wgExtensionFunctions[] = function() {
 		};
 	}
 
+	// If EventLogging integration is enabled, first ensure that the
+	// EventLogging extension is present, then declare schema module.
+	// If it is not present, emit a warning and disable logging.
+	if ( $wgULSEventLogging ) {
+		if ( class_exists( 'ResourceLoaderSchemaModule' ) ) {
+			/// @see https://meta.wikimedia.org/wiki/Schema:UniversalLanguageSelector
+			$wgResourceModules['schema.UniversalLanguageSelector'] = array(
+				'class'  => 'ResourceLoaderSchemaModule',
+				'schema' => 'UniversalLanguageSelector',
+				'revision' => 5573536,
+			);
+		} else {
+			wfWarn( 'UniversalLanguageSelector is configured to use EventLogging, but '
+					. 'the extension is is not available. Disabling wgULSEventLogging.' );
+			$wgULSEventLogging = false;
+		}
+	}
+
 	return true;
 };