From e04d6c318695a06f2cdd43f4e7785bd2eec123ca Mon Sep 17 00:00:00 2001
From: Timo Tijhof <krinklemail@gmail.com>
Date: Sun, 25 Aug 2019 17:24:55 +0100
Subject: [PATCH] resourceloader: Compile documentElement.className server-side

Reduces output by not needlessly performing a change client-side
for which we already know the result server-side.

Bug: T231168
Change-Id: I4b8749f976d04d24f85236ddd641c7a4c7f6c23a
---
 includes/OutputPage.php                             |  7 ++++---
 .../resourceloader/ResourceLoaderClientHtml.php     | 13 ++++++++-----
 .../resourceloader/ResourceLoaderClientHtmlTest.php |  8 ++++----
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/includes/OutputPage.php b/includes/OutputPage.php
index 3f2dcf7f4b..d63d376b62 100644
--- a/includes/OutputPage.php
+++ b/includes/OutputPage.php
@@ -3027,10 +3027,11 @@ class OutputPage extends ContextSource {
 		$sitedir = MediaWikiServices::getInstance()->getContentLanguage()->getDir();
 
 		$pieces = [];
-		$pieces[] = Html::htmlHeader( Sanitizer::mergeAttributes(
+		$htmlAttribs = Sanitizer::mergeAttributes(
 			$this->getRlClient()->getDocumentAttributes(),
 			$sk->getHtmlElementAttributes()
-		) );
+		);
+		$pieces[] = Html::htmlHeader( $htmlAttribs );
 		$pieces[] = Html::openElement( 'head' );
 
 		if ( $this->getHTMLTitle() == '' ) {
@@ -3050,7 +3051,7 @@ class OutputPage extends ContextSource {
 		}
 
 		$pieces[] = Html::element( 'title', null, $this->getHTMLTitle() );
-		$pieces[] = $this->getRlClient()->getHeadHtml();
+		$pieces[] = $this->getRlClient()->getHeadHtml( $htmlAttribs['class'] ?? null );
 		$pieces[] = $this->buildExemptModules();
 		$pieces = array_merge( $pieces, array_values( $this->getHeadLinksArray() ) );
 		$pieces = array_merge( $pieces, array_values( $this->mHeadItems ) );
diff --git a/includes/resourceloader/ResourceLoaderClientHtml.php b/includes/resourceloader/ResourceLoaderClientHtml.php
index e17b393a57..151b5fd502 100644
--- a/includes/resourceloader/ResourceLoaderClientHtml.php
+++ b/includes/resourceloader/ResourceLoaderClientHtml.php
@@ -240,19 +240,22 @@ class ResourceLoaderClientHtml {
 	 * - Inline scripts can't be asynchronous.
 	 * - For styles, earlier is better.
 	 *
+	 * @param string|null $nojsClass Class name that caller uses on HTML document element
 	 * @return string|WrappedStringList HTML
 	 */
-	public function getHeadHtml() {
+	public function getHeadHtml( $nojsClass = null ) {
 		$nonce = $this->options['nonce'];
 		$data = $this->getData();
 		$chunks = [];
 
 		// Change "client-nojs" class to client-js. This allows easy toggling of UI components.
 		// This must happen synchronously on every page view to avoid flashes of wrong content.
-		// See also #getDocumentAttributes() and /resources/src/startup.js.
-		$script = <<<'JAVASCRIPT'
-document.documentElement.className = document.documentElement.className
-	.replace( /(^|\s)client-nojs(\s|$)/, "$1client-js$2" );
+		// See also startup/startup.js.
+		$nojsClass = $nojsClass ?? $this->getDocumentAttributes()['class'];
+		$jsClass = preg_replace( '/(^|\s)client-nojs(\s|$)/', '$1client-js$2', $nojsClass );
+		$jsClassJson = ResourceLoader::encodeJsonForScript( $jsClass );
+		$script = <<<JAVASCRIPT
+document.documentElement.className = {$jsClassJson};
 JAVASCRIPT;
 
 		// Inline script: Declare mw.config variables for this page.
diff --git a/tests/phpunit/includes/resourceloader/ResourceLoaderClientHtmlTest.php b/tests/phpunit/includes/resourceloader/ResourceLoaderClientHtmlTest.php
index e1ee3248cc..4152cdf664 100644
--- a/tests/phpunit/includes/resourceloader/ResourceLoaderClientHtmlTest.php
+++ b/tests/phpunit/includes/resourceloader/ResourceLoaderClientHtmlTest.php
@@ -108,7 +108,7 @@ Deprecation message.' ]
 
 		// phpcs:disable Generic.Files.LineLength
 		$expected = '<script>'
-			. 'document.documentElement.className=document.documentElement.className.replace(/(^|\s)client-nojs(\s|$)/,"$1client-js$2");'
+			. 'document.documentElement.className="client-js";'
 			. 'RLCONF={"key":"value"};'
 			. 'RLSTATE={"test.exempt":"ready","test.private":"loading","test.styles.pure":"ready","test.styles.private":"ready","test.styles.deprecated":"ready"};'
 			. 'RLPAGEMODULES=["test"];'
@@ -135,7 +135,7 @@ Deprecation message.' ]
 		);
 
 		// phpcs:disable Generic.Files.LineLength
-		$expected = '<script>document.documentElement.className=document.documentElement.className.replace(/(^|\s)client-nojs(\s|$)/,"$1client-js$2");</script>' . "\n"
+		$expected = '<script>document.documentElement.className="client-js";</script>' . "\n"
 			. '<script async="" src="/w/load.php?lang=nl&amp;modules=startup&amp;only=scripts&amp;raw=1&amp;target=example"></script>';
 		// phpcs:enable
 
@@ -152,7 +152,7 @@ Deprecation message.' ]
 		);
 
 		// phpcs:disable Generic.Files.LineLength
-		$expected = '<script>document.documentElement.className=document.documentElement.className.replace(/(^|\s)client-nojs(\s|$)/,"$1client-js$2");</script>' . "\n"
+		$expected = '<script>document.documentElement.className="client-js";</script>' . "\n"
 			. '<script async="" src="/w/load.php?lang=nl&amp;modules=startup&amp;only=scripts&amp;raw=1&amp;safemode=1"></script>';
 		// phpcs:enable
 
@@ -169,7 +169,7 @@ Deprecation message.' ]
 		);
 
 		// phpcs:disable Generic.Files.LineLength
-		$expected = '<script>document.documentElement.className=document.documentElement.className.replace(/(^|\s)client-nojs(\s|$)/,"$1client-js$2");</script>' . "\n"
+		$expected = '<script>document.documentElement.className="client-js";</script>' . "\n"
 			. '<script async="" src="/w/load.php?lang=nl&amp;modules=startup&amp;only=scripts&amp;raw=1"></script>';
 		// phpcs:enable
 
-- 
2.20.1