Ensure that first content image is not lazy-loaded in block themes either

src/wp-includes/block-template.php

@@ -241,7 +241,7 @@ function get_the_block_template_html() {
 	$content = wptexturize( $content );
 	$content = convert_smilies( $content );
 	$content = shortcode_unautop( $content );
-	$content = wp_filter_content_tags( $content );
+	$content = wp_filter_content_tags( $content, 'template' );
 	$content = do_shortcode( $content );
 	$content = str_replace( ']]>', ']]>', $content );
 

src/wp-includes/media.php

@@ -5444,25 +5444,40 @@ function wp_get_webp_info( $filename ) {
  *                     that the `loading` attribute should be skipped.
  */
 function wp_get_loading_attr_default( $context ) {
-	// Only elements with 'the_content' or 'the_post_thumbnail' context have special handling.
-	if ( 'the_content' !== $context && 'the_post_thumbnail' !== $context ) {
-		return 'lazy';
+	// Skip lazy-loading for the overall block template, as it is handled more granularly.
+	if ( 'template' === $context ) {
+		return false;
 	}
 
-	// Only elements within the main query loop have special handling.
-	if ( is_admin() || ! in_the_loop() || ! is_main_query() ) {
-		return 'lazy';
+	// Do not lazy-load images in the header block template part, as they are likely above the fold.
+	$header_area = WP_TEMPLATE_PART_AREA_HEADER;
+	if ( "template_part_{$header_area}" === $context ) {
+		return false;
 	}
 
-	// Increase the counter since this is a main query content element.
-	$content_media_count = wp_increase_content_media_count();
+	/*
+	 * The first elements in 'the_content' or 'the_post_thumbnail' should not be lazy-loaded,
+	 * as they are likely above the fold.
+	 */
+	if ( 'the_content' === $context || 'the_post_thumbnail' === $context ) {
+		// Only elements within the main query loop have special handling.
+		if ( is_admin() || ! in_the_loop() || ! is_main_query() ) {
+			return 'lazy';
+		}
 
-	// If the count so far is below the threshold, return `false` so that the `loading` attribute is omitted.
-	if ( $content_media_count <= wp_omit_loading_attr_threshold() ) {
-		return false;
+		// Increase the counter since this is a main query content element.
+		$content_media_count = wp_increase_content_media_count();
+
+		// If the count so far is below the threshold, return `false` so that the `loading` attribute is omitted.
+		if ( $content_media_count <= wp_omit_loading_attr_threshold() ) {
+			return false;
+		}
+
+		// For elements after the threshold, lazy-load them as usual.
+		return 'lazy';
 	}
 
-	// For elements after the threshold, lazy-load them as usual.
+	// Lazy-load by default for any unknown context.
 	return 'lazy';
 }
 

tests/phpunit/tests/media.php

@@ -3547,7 +3547,13 @@ public function data_attachment_permalinks_based_on_parent_status() {
 	}
 
 	/**
+	 * Tests that wp_get_loading_attr_default() returns the expected loading attribute value.
+	 *
 	 * @ticket 53675
+	 * @ticket 56930
+	 *
+	 * @covers ::wp_get_loading_attr_default
+	 *
 	 * @dataProvider data_wp_get_loading_attr_default
 	 *
 	 * @param string $context
@@ -3588,6 +3594,10 @@ public function test_wp_get_loading_attr_default( $context ) {
 			// Yes, for all subsequent elements.
 			$this->assertSame( 'lazy', wp_get_loading_attr_default( $context ) );
 		}
+
+		// Exceptions: In the following contexts, images shouldn't be lazy-loaded by default.
+		$this->assertFalse( wp_get_loading_attr_default( 'template' ), 'Images run through the overall block template filter should not be lazy-loaded.' );
+		$this->assertFalse( wp_get_loading_attr_default( 'template_part_' . WP_TEMPLATE_PART_AREA_HEADER ), 'Images in the footer block template part should not be lazy-loaded.' );
 	}
 
 	public function data_wp_get_loading_attr_default() {
@@ -3700,6 +3710,159 @@ function() {
 		$this->assertSame( 3, $omit_threshold );
 	}
 
+	/**
+	 * Tests that wp_filter_content_tags() does not add loading="lazy" to the first
+	 * image in the loop when using a block theme.
+	 *
+	 * @ticket 56930
+	 *
+	 * @covers ::wp_filter_content_tags
+	 * @covers ::wp_get_loading_attr_default
+	 */
+	public function test_wp_filter_content_tags_does_not_lazy_load_first_image_in_block_theme() {
+		global $_wp_current_template_content, $wp_query, $wp_the_query, $post;
+
+		// Do not add srcset, sizes, or decoding attributes as they are irrelevant for this test.
+		add_filter( 'wp_img_tag_add_srcset_and_sizes_attr', '__return_false' );
+		add_filter( 'wp_img_tag_add_decoding_attr', '__return_false' );
+
+		$img1      = get_image_tag( self::$large_id, '', '', '', 'large' );
+		$img2      = get_image_tag( self::$large_id, '', '', '', 'medium' );
+		$lazy_img2 = wp_img_tag_add_loading_attr( $img2, 'the_content' );
+
+		// Only the second image should be lazy-loaded.
+		$post_content     = $img1 . $img2;
+		$expected_content = wpautop( $img1 . $lazy_img2 );
+
+		// Update the post to test with so that it has the above post content.
+		wp_update_post(
+			array(
+				'ID'                    => self::$post_ids['publish'],
+				'post_content'          => $post_content,
+				'post_content_filtered' => $post_content,
+			)
+		);
+
+		$wp_query     = new WP_Query( array( 'p' => self::$post_ids['publish'] ) );
+		$wp_the_query = $wp_query;
+		$post         = get_post( self::$post_ids['publish'] );
+		$this->reset_content_media_count();
+		$this->reset_omit_loading_attr_filter();
+
+		$_wp_current_template_content = '<!-- wp:post-content /-->';
+
+		$html = get_the_block_template_html();
+		$this->assertSame( '<div class="wp-site-blocks"><div class="is-layout-flow entry-content wp-block-post-content">' . $expected_content . '</div></div>', $html );
+	}
+
+	/**
+	 * Tests that wp_filter_content_tags() does not add loading="lazy"
+	 * to the featured image when using a block theme.
+	 *
+	 * @ticket 56930
+	 *
+	 * @covers ::wp_filter_content_tags
+	 * @covers ::wp_get_loading_attr_default
+	 */
+	public function test_wp_filter_content_tags_does_not_lazy_load_first_featured_image_in_block_theme() {
+		global $_wp_current_template_content, $wp_query, $wp_the_query, $post;
+
+		// Do not add srcset, sizes, or decoding attributes as they are irrelevant for this test.
+		add_filter( 'wp_img_tag_add_srcset_and_sizes_attr', '__return_false' );
+		add_filter( 'wp_img_tag_add_decoding_attr', '__return_false' );
+		add_filter(
+			'wp_get_attachment_image_attributes',
+			function( $attr ) {
+				unset( $attr['srcset'], $attr['sizes'], $attr['decoding'] );
+				return $attr;
+			}
+		);
+
+		$content_img      = get_image_tag( self::$large_id, '', '', '', 'large' );
+		$lazy_content_img = wp_img_tag_add_loading_attr( $content_img, 'the_content' );
+
+		// The featured image should not be lazy-loaded as it is the first image.
+		$featured_image_id = self::$large_id;
+		update_post_meta( self::$post_ids['publish'], '_thumbnail_id', $featured_image_id );
+		$expected_featured_image = '<figure class="wp-block-post-featured-image">' . get_the_post_thumbnail( self::$post_ids['publish'], 'post-thumbnail', array( 'loading' => false ) ) . '</figure>';
+
+		// The post content image should be lazy-loaded since the featured image appears above.
+		$post_content     = $content_img;
+		$expected_content = wpautop( $lazy_content_img );
+
+		// Update the post to test with so that it has the above post content.
+		wp_update_post(
+			array(
+				'ID'                    => self::$post_ids['publish'],
+				'post_content'          => $post_content,
+				'post_content_filtered' => $post_content,
+			)
+		);
+
+		$wp_query     = new WP_Query( array( 'p' => self::$post_ids['publish'] ) );
+		$wp_the_query = $wp_query;
+		$post         = get_post( self::$post_ids['publish'] );
+		$this->reset_content_media_count();
+		$this->reset_omit_loading_attr_filter();
+
+		$_wp_current_template_content = '<!-- wp:post-featured-image /--> <!-- wp:post-content /-->';
+
+		$html = get_the_block_template_html();
+		$this->assertSame( '<div class="wp-site-blocks">' . $expected_featured_image . ' <div class="is-layout-flow entry-content wp-block-post-content">' . $expected_content . '</div></div>', $html );
+	}
+
+	/**
+	 * Tests that wp_filter_content_tags() does not add loading="lazy" to images
+	 * in a "Header" template part.
+	 *
+	 * @ticket 56930
+	 *
+	 * @covers ::wp_filter_content_tags
+	 * @covers ::wp_get_loading_attr_default
+	 */
+	public function test_wp_filter_content_tags_does_not_lazy_load_images_in_header() {
+		global $_wp_current_template_content;
+
+		// Do not add srcset, sizes, or decoding attributes as they are irrelevant for this test.
+		add_filter( 'wp_img_tag_add_srcset_and_sizes_attr', '__return_false' );
+		add_filter( 'wp_img_tag_add_decoding_attr', '__return_false' );
+
+		// Use a single image for each header and footer template parts.
+		$header_img = get_image_tag( self::$large_id, '', '', '', 'large' );
+		$footer_img = get_image_tag( self::$large_id, '', '', '', 'medium' );
+
+		// Create header and footer template parts.
+		$header_post_id = self::factory()->post->create(
+			array(
+				'post_type'    => 'wp_template_part',
+				'post_status'  => 'publish',
+				'post_name'    => 'header',
+				'post_content' => $header_img,
+			)
+		);
+		wp_set_post_terms( $header_post_id, WP_TEMPLATE_PART_AREA_HEADER, 'wp_template_part_area' );
+		wp_set_post_terms( $header_post_id, get_stylesheet(), 'wp_theme' );
+		$footer_post_id = self::factory()->post->create(
+			array(
+				'post_type'    => 'wp_template_part',
+				'post_status'  => 'publish',
+				'post_name'    => 'footer',
+				'post_content' => $footer_img,
+			)
+		);
+		wp_set_post_terms( $footer_post_id, WP_TEMPLATE_PART_AREA_FOOTER, 'wp_template_part_area' );
+		wp_set_post_terms( $footer_post_id, get_stylesheet(), 'wp_theme' );
+
+		$_wp_current_template_content = '<!-- wp:template-part {"slug":"header","theme":"' . get_stylesheet() . '","tagName":"header"} /--><!-- wp:template-part {"slug":"footer","theme":"' . get_stylesheet() . '","tagName":"footer"} /-->';
+
+		// Header image should not be lazy-loaded, footer image should be lazy-loaded.
+		$expected_template_content  = '<header class="wp-block-template-part">' . $header_img . '</header>';
+		$expected_template_content .= '<footer class="wp-block-template-part">' . wp_img_tag_add_loading_attr( $footer_img, 'force-lazy' ) . '</footer>';
+
+		$html = get_the_block_template_html();
+		$this->assertSame( '<div class="wp-site-blocks">' . $expected_template_content . '</div>', $html );
+	}
+
 	private function reset_content_media_count() {
 		// Get current value without increasing.
 		$content_media_count = wp_increase_content_media_count( 0 );