From b92c1c58b3c14b578161de356d6afd861307bf1a Mon Sep 17 00:00:00 2001
From: Peter Wilson <peterwilsoncc@git.wordpress.org>
Date: Tue, 19 Jul 2016 02:34:42 +0000
Subject: [PATCH] Script Loader: Limit resource hinting to enqueued assets.

Externally hosted script and style dependencies trigger `dns-prefetch` hinting only when enqueued. This removed a bug in which hinting was added on registration.

Renames the function `wp_resource_hints_scripts_styles` to `wp_dependencies_unique_hosts` as the function provides the hosts, not the hinting.

Props swissspidy.
Fixes #37385.


git-svn-id: https://develop.svn.wordpress.org/trunk@38100 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/general-template.php          | 32 ++++++++-----------
 tests/phpunit/tests/general/resourceHints.php | 13 ++++++++
 2 files changed, 27 insertions(+), 18 deletions(-)

diff --git a/src/wp-includes/general-template.php b/src/wp-includes/general-template.php
index 2bcdb43801..ca48499ed3 100644
--- a/src/wp-includes/general-template.php
+++ b/src/wp-includes/general-template.php
@@ -2799,7 +2799,7 @@ function wp_site_icon() {
  */
 function wp_resource_hints() {
 	$hints = array(
-		'dns-prefetch' => wp_resource_hints_scripts_styles(),
+		'dns-prefetch' => wp_dependencies_unique_hosts(),
 		'preconnect'   => array( 's.w.org' ),
 		'prefetch'     => array(),
 		'prerender'    => array(),
@@ -2851,31 +2851,27 @@ function wp_resource_hints() {
 }
 
 /**
- * Adds dns-prefetch for all scripts and styles enqueued from external hosts.
+ * Returns a list of unique hosts of all enqueued scripts and styles.
  *
  * @since 4.6.0
+ *
+ * @return array A list of unique hosts of enqueued scripts and styles.
  */
-function wp_resource_hints_scripts_styles() {
+function wp_dependencies_unique_hosts() {
 	global $wp_scripts, $wp_styles;
 
 	$unique_hosts = array();
 
-	if ( is_object( $wp_scripts ) && ! empty( $wp_scripts->registered ) ) {
-		foreach ( $wp_scripts->registered as $registered_script ) {
-			$parsed = wp_parse_url( $registered_script->src );
+	foreach ( array( $wp_scripts, $wp_styles ) as $dependencies ) {
+		if ( $dependencies instanceof WP_Dependencies && ! empty( $dependencies->queue ) ) {
+			foreach ( $dependencies->queue as $handle ) {
+				/* @var _WP_Dependency $dependency */
+				$dependency = $dependencies->registered[ $handle ];
+				$parsed     = wp_parse_url( $dependency->src );
 
-			if ( ! empty( $parsed['host'] ) && ! in_array( $parsed['host'], $unique_hosts ) && $parsed['host'] !== $_SERVER['SERVER_NAME'] ) {
-				$unique_hosts[] = $parsed['host'];
-			}
-		}
-	}
-
-	if ( is_object( $wp_styles ) && ! empty( $wp_styles->registered ) ) {
-		foreach ( $wp_styles->registered as $registered_style ) {
-			$parsed = wp_parse_url( $registered_style->src );
-
-			if ( ! empty( $parsed['host'] ) && ! in_array( $parsed['host'], $unique_hosts ) && $parsed['host'] !== $_SERVER['SERVER_NAME'] ) {
-				$unique_hosts[] = $parsed['host'];
+				if ( ! empty( $parsed['host'] ) && ! in_array( $parsed['host'], $unique_hosts ) && $parsed['host'] !== $_SERVER['SERVER_NAME'] ) {
+					$unique_hosts[] = $parsed['host'];
+				}
 			}
 		}
 	}
diff --git a/tests/phpunit/tests/general/resourceHints.php b/tests/phpunit/tests/general/resourceHints.php
index 7041a6130e..95958e7f6b 100644
--- a/tests/phpunit/tests/general/resourceHints.php
+++ b/tests/phpunit/tests/general/resourceHints.php
@@ -150,4 +150,17 @@ class Tests_WP_Resource_Hints extends WP_UnitTestCase {
 		$this->assertEquals( $expected, $actual );
 	}
 
+	function test_dns_prefetch_scripts_does_not_included_registered_only() {
+		$expected = "<link rel='preconnect' href='http://s.w.org'>\n";
+		$unexpected = "<link rel='dns-prefetch' href='//wordpress.org'>\n";
+
+		wp_register_script( 'jquery-elsewhere', 'https://wordpress.org/wp-includes/js/jquery/jquery.js' );
+
+		$actual = get_echo( 'wp_resource_hints' );
+
+		wp_deregister_script( 'jquery-elsewhere' );
+
+		$this->assertEquals( $expected, $actual );
+		$this->assertNotContains( $unexpected, $actual );
+	}
 }