From ed174730d3c2bca27290ece3b88a8f97fa976be9 Mon Sep 17 00:00:00 2001
From: Joe McGill <joemcgill@git.wordpress.org>
Date: Tue, 11 Jul 2023 13:56:55 +0000
Subject: [PATCH] Media: Optimize images created in shortcodes.

This fixes an issue where images dynamically created during shortcode rendering (e.g., shortcode image galleries), were not getting image optimizations like `loading="lazy"` or `fetchpriority="hight"` applied. Note that even after this commit, shortcodes are processed after the main content images, which can affect the order in which optimizations are applied in content areas.

Follow-up to [56037].

Props spacedmonkey, flixos90, thekt12, swissspidy, joemcgill.
Fixes #58681.


git-svn-id: https://develop.svn.wordpress.org/trunk@56214 602fd350-edb4-49c9-b593-d223f7449a82
---
 src/wp-includes/media.php      |   5 +-
 src/wp-includes/shortcodes.php |  28 ++++++++
 tests/phpunit/tests/media.php  | 120 ++++++++++++++++++++++++++++++++-
 3 files changed, 149 insertions(+), 4 deletions(-)

diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 1dc610f550..b706cd9897 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -5725,9 +5725,10 @@ function wp_get_loading_optimization_attributes( $tag_name, $attr, $context ) {
 
 	/*
 	 * The first elements in 'the_content' or 'the_post_thumbnail' should not be lazy-loaded,
-	 * as they are likely above the fold.
+	 * as they are likely above the fold. Shortcodes are processed after content images, so if
+	 * thresholds haven't already been met, apply the same logic to those as well.
 	 */
-	if ( 'the_content' === $context || 'the_post_thumbnail' === $context ) {
+	if ( 'the_content' === $context || 'the_post_thumbnail' === $context || 'do_shortcode' === $context ) {
 		// Only elements within the main query loop have special handling.
 		if ( is_admin() || ! in_the_loop() || ! is_main_query() ) {
 			$loading_attrs['loading'] = 'lazy';
diff --git a/src/wp-includes/shortcodes.php b/src/wp-includes/shortcodes.php
index ea55f3373a..4d23521f44 100644
--- a/src/wp-includes/shortcodes.php
+++ b/src/wp-includes/shortcodes.php
@@ -221,6 +221,14 @@ function do_shortcode( $content, $ignore_html = false ) {
 		return $content;
 	}
 
+	// Ensure this context is only added once if shortcodes are nested.
+	$has_filter = has_filter( 'wp_get_attachment_image_context', '_filter_do_shortcode_context' );
+	$filter_added = false;
+
+	if ( ! $has_filter ) {
+		$filter_added = add_filter( 'wp_get_attachment_image_context', '_filter_do_shortcode_context' );
+	}
+
 	$content = do_shortcodes_in_html_tags( $content, $ignore_html, $tagnames );
 
 	$pattern = get_shortcode_regex( $tagnames );
@@ -229,9 +237,29 @@ function do_shortcode( $content, $ignore_html = false ) {
 	// Always restore square braces so we don't break things like <!--[if IE ]>.
 	$content = unescape_invalid_shortcodes( $content );
 
+	// Only remove the filter if it was added in this scope.
+	if ( $filter_added ) {
+		remove_filter( 'wp_get_attachment_image_context', '_filter_do_shortcode_context' );
+	}
+
 	return $content;
 }
 
+/**
+ * Filter the `wp_get_attachment_image_context` hook during shortcode rendering.
+ *
+ * When wp_get_attachment_image() is called during shortcode rendering, we need to make clear
+ * that the context is a shortcode and not part of the theme's template rendering logic.
+ *
+ * @since 6.3.0
+ * @access private
+ *
+ * @return string The filtered context value for wp_get_attachment_images when doing shortcodes.
+ */
+function _filter_do_shortcode_context() {
+	return 'do_shortcode';
+}
+
 /**
  * Retrieves the shortcode regular expression for searching.
  *
diff --git a/tests/phpunit/tests/media.php b/tests/phpunit/tests/media.php
index 30d8a5f343..f59eb78a95 100644
--- a/tests/phpunit/tests/media.php
+++ b/tests/phpunit/tests/media.php
@@ -78,8 +78,8 @@ CAP;
 	/**
 	 * Ensures that the static content media count, fetchpriority element flag and related filter are reset between tests.
 	 */
-	public function set_up() {
-		parent::set_up();
+	public function tear_down() {
+		parent::tear_down();
 
 		$this->reset_content_media_count();
 		$this->reset_omit_loading_attr_filter();
@@ -5005,6 +5005,122 @@ EOF;
 		);
 	}
 
+	/**
+	 * @ticket 58681
+	 *
+	 * @dataProvider data_wp_get_loading_optimization_attributes_in_shortcodes
+	 */
+	public function test_wp_get_loading_optimization_attributes_in_shortcodes( $setup, $expected, $message ) {
+		$attr = $this->get_width_height_for_high_priority();
+		$setup();
+
+		// The first image processed in a shortcode should have fetchpriority set to high.
+		$this->assertSame(
+			$expected,
+			wp_get_loading_optimization_attributes( 'img', $attr, 'do_shortcode' ),
+			$message
+		);
+	}
+
+	public function data_wp_get_loading_optimization_attributes_in_shortcodes() {
+		return array(
+			'main_shortcode_image_should_have_fetchpriority_high'  => array(
+				'setup'    => function () {
+					global $wp_query;
+
+					// Set WP_Query to be in the loop and the main query.
+					$wp_query->in_the_loop = true;
+					$this->set_main_query( $wp_query );
+				},
+				'expected' => array(
+					'fetchpriority' => 'high',
+				),
+				'message'  => 'Fetch priority not applied to during shortcode rendering.',
+			),
+			'main_shortcode_image_after_threshold_is_loading_lazy' => array(
+				'setup'    => function () {
+					global $wp_query;
+
+					// Set WP_Query to be in the loop and the main query.
+					$wp_query->in_the_loop = true;
+					$this->set_main_query( $wp_query );
+
+					// Set internal flags so lazy should be applied.
+					wp_high_priority_element_flag( false );
+					wp_increase_content_media_count( 3 );
+				},
+				'expected' => array(
+					'loading' => 'lazy',
+				),
+				'message'  => 'Lazy-loading not applied to during shortcode rendering.',
+			),
+			'shortcode_image_outside_of_the_loop_are_loaded_lazy'  => array(
+				'setup'    => function () {
+					// Avoid setting up the WP_Query object for the loop.
+					return;
+				},
+				'expected' => array(
+					'loading' => 'lazy',
+				),
+				'message'  => 'Lazy-loading not applied to shortcodes outside the loop.',
+			),
+		);
+	}
+
+	/**
+	 * @ticket 58681
+	 */
+	public function test_content_rendering_with_shortcodes() {
+		// The gallery shortcode will dynamically create image markup that should be optimized.
+		$content = "[gallery ids='" . self::$large_id . "' size='large']";
+		$actual  = apply_filters( 'the_content', $content );
+
+		$this->assertStringContainsString(
+			// Since the main query and loop isn't set, this should be lazily loaded.
+			'loading="lazy"',
+			$actual,
+			'Could not confirm shortcodes get optimizations applied.'
+		);
+	}
+
+	/**
+	 * @ticket 58681
+	 */
+	public function test_content_rendering_with_shortcodes_nested() {
+		global $wp_query;
+
+		// Set WP_Query to be in the loop and the main query.
+		$wp_query->in_the_loop = true;
+		$this->set_main_query( $wp_query );
+
+		add_shortcode(
+			'div',
+			function ( $atts, $content = null ) {
+				$parsed_atts = shortcode_atts(
+					array(
+						'class' => '',
+					),
+					$atts
+				);
+
+				$class = ! empty( $parsed_atts['class'] ) ? sprintf( ' class="%s"', $parsed_atts['class'] ) : null;
+
+				return sprintf( '<div %s>%s</div>', $class, do_shortcode( $content ) );
+			}
+		);
+
+		// The gallery shortcode will dynamically create image markup that should be optimized.
+		$content = "[div][gallery ids='" . self::$large_id . "' size='large'][div]";
+		$actual  = apply_filters( 'the_content', $content );
+
+		$this->assertStringContainsString(
+			// Since this is in the loop, it should have a high fetchpriority.
+			'fetchpriority="high"',
+			$actual,
+			'Could not confirm shortcodes get optimizations applied.'
+		);
+	}
+
 	/**
 	 * @ticket 58235
 	 *