From 9ea68bc533a5c50eca14d2ba4c86ad958bbbdb38 Mon Sep 17 00:00:00 2001
From: Pascal Birchler <pascal.birchler@gmail.com>
Date: Fri, 15 Jan 2016 10:23:25 +0000
Subject: [PATCH] Script Loader: Add `Etag: $wp_version` header in
 `load-scripts.php` and `load-styles.php`.

This improves performance since browsers won't re-download the scripts and styles when there was no change in `$wp_version`.

Props sergej.mueller, dd32, swissspidy.
Fixes #28722.
Built from https://develop.svn.wordpress.org/trunk@36312


git-svn-id: http://core.svn.wordpress.org/trunk@36279 1a063a9b-81f0-0310-95a4-ce76da25c4cd
---
 wp-admin/load-scripts.php | 10 ++++++++++
 wp-admin/load-styles.php  | 10 ++++++++++
 wp-includes/version.php   |  2 +-
 3 files changed, 21 insertions(+), 1 deletion(-)

diff --git a/wp-admin/load-scripts.php b/wp-admin/load-scripts.php
index 4c7d40ed61..011ae3c890 100644
--- a/wp-admin/load-scripts.php
+++ b/wp-admin/load-scripts.php
@@ -33,6 +33,15 @@ $out = '';
 $wp_scripts = new WP_Scripts();
 wp_default_scripts($wp_scripts);
 
+if ( isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) && stripslashes( $_SERVER['HTTP_IF_NONE_MATCH'] ) === $wp_version ) {
+	$protocol = $_SERVER['SERVER_PROTOCOL'];
+	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ) ) ) {
+		$protocol = 'HTTP/1.0';
+	}
+	header( "$protocol 304 Not Modified" );
+	exit();
+}
+
 foreach ( $load as $handle ) {
 	if ( !array_key_exists($handle, $wp_scripts->registered) )
 		continue;
@@ -41,6 +50,7 @@ foreach ( $load as $handle ) {
 	$out .= get_file($path) . "\n";
 }
 
+header("Etag: $wp_version");
 header('Content-Type: application/javascript; charset=UTF-8');
 header('Expires: ' . gmdate( "D, d M Y H:i:s", time() + $expires_offset ) . ' GMT');
 header("Cache-Control: public, max-age=$expires_offset");
diff --git a/wp-admin/load-styles.php b/wp-admin/load-styles.php
index 2563e6f6db..7d7d4045bd 100644
--- a/wp-admin/load-styles.php
+++ b/wp-admin/load-styles.php
@@ -30,6 +30,15 @@ $out = '';
 $wp_styles = new WP_Styles();
 wp_default_styles($wp_styles);
 
+if ( isset( $_SERVER['HTTP_IF_NONE_MATCH'] ) && stripslashes( $_SERVER['HTTP_IF_NONE_MATCH'] ) === $wp_version ) {
+	$protocol = $_SERVER['SERVER_PROTOCOL'];
+	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ) ) ) {
+		$protocol = 'HTTP/1.0';
+	}
+	header( "$protocol 304 Not Modified" );
+	exit();
+}
+
 foreach ( $load as $handle ) {
 	if ( !array_key_exists($handle, $wp_styles->registered) )
 		continue;
@@ -54,6 +63,7 @@ foreach ( $load as $handle ) {
 	}
 }
 
+header("Etag: $wp_version");
 header('Content-Type: text/css; charset=UTF-8');
 header('Expires: ' . gmdate( "D, d M Y H:i:s", time() + $expires_offset ) . ' GMT');
 header("Cache-Control: public, max-age=$expires_offset");
diff --git a/wp-includes/version.php b/wp-includes/version.php
index c4cedb0429..0422d06dfe 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.5-alpha-36311';
+$wp_version = '4.5-alpha-36312';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.