OutputPage: Move hardcoded default modules to Skin::getDefaultModules

These modules should not be hardcoded in OutputPage::output() which
makes them impossible to override and also very hard to retrieve
through the API for action=parse. Move these instead to Skin which
is where all other default module loading happens already.

Moving these modules is in preparation for customising ApiParse
to support "really" returning all would-be loaded modules on a page
when setting 'useskin', which is also needed for Live Preview
and in theory for ajax navigation and other scenarios where there
is a delay between the "initial" page rendering, and a later re-render
which may not have all all the necessary modules.

Bug: T130632
Change-Id: Ic4afccf0cd0d428d7fbc36d4e747415af3ab49f5

includes/OutputPage.php

@@ -2405,26 +2405,10 @@ public function output( $return = false ) {
 			}
 
 			$sk = $this->getSkin();
-			// add skin specific modules
-			$modules = $sk->getDefaultModules();
-
-			// Enforce various default modules for all pages and all skins
-			$coreModules = [
-				// Keep this list as small as possible
-				'site',
-				'mediawiki.page.startup',
-				'mediawiki.user',
-			];
-
-			// Support for high-density display images if enabled
-			if ( $config->get( 'ResponsiveImages' ) ) {
-				$coreModules[] = 'mediawiki.hidpi';
-			}
-
-			$this->addModules( $coreModules );
-			foreach ( $modules as $group ) {
+			foreach ( $sk->getDefaultModules() as $group ) {
 				$this->addModules( $group );
 			}
+
 			MWDebug::addModules( $this );
 
 			// Avoid PHP 7.1 warning of passing $this by reference

includes/skins/Skin.php

@@ -158,8 +158,17 @@ public function getDefaultModules() {
 		global $wgUseAjax, $wgEnableAPI, $wgEnableWriteAPI;
 
 		$out = $this->getOutput();
+		$config = $this->getConfig();
 		$user = $out->getUser();
 		$modules = [
+			// modules not specific to any specific skin or page
+			'core' => [
+				// Enforce various default modules for all pages and all skins
+				// Keep this list as small as possible
+				'site',
+				'mediawiki.page.startup',
+				'mediawiki.user',
+			],
 			// modules that enhance the page content in some way
 			'content' => [
 				'mediawiki.page.ready',
@@ -172,6 +181,11 @@ public function getDefaultModules() {
 			'user' => [],
 		];
 
+		// Support for high-density display images if enabled
+		if ( $config->get( 'ResponsiveImages' ) ) {
+			$modules['core'][] = 'mediawiki.hidpi';
+		}
+
 		// Preload jquery.tablesorter for mediawiki.page.ready
 		if ( strpos( $out->getHTML(), 'sortable' ) !== false ) {
 			$modules['content'][] = 'jquery.tablesorter';