Merge pull request #316 from WordPress/fix/288-featured-image-in-webp

Replace the featured image with WebP version when available

modules/images/webp-uploads/load.php

@@ -502,3 +502,19 @@ function webp_uploads_img_tag_update_mime_type( $image, $context, $attachment_id
 
 	return $image;
 }
+
+/**
+ * Updates the references of the featured image to the a new image format if available, in the same way it
+ * occurs in the_content of a post.
+ *
+ * @since n.e.x.t
+ *
+ * @param string $html          The current HTML markup of the featured image.
+ * @param int    $post_id       The current post ID where the featured image is requested.
+ * @param int    $attachment_id The ID of the attachment image.
+ * @return string The updated HTML markup.
+ */
+function webp_uploads_update_featured_image( $html, $post_id, $attachment_id ) {
+	return webp_uploads_img_tag_update_mime_type( $html, 'post_thumbnail_html', $attachment_id );
+}
+add_filter( 'post_thumbnail_html', 'webp_uploads_update_featured_image', 10, 3 );

tests/modules/images/webp-uploads/load-tests.php

@@ -662,4 +662,21 @@ function( $data, $attachment_id ) {
 		$this->assertNotContains( 'image/invalid', $mime_types );
 		$this->assertSame( array( 'image/jpeg', 'image/webp' ), $mime_types );
 	}
+
+	/**
+	 * Replace the featured image to WebP when requesting the featured image
+	 *
+	 * @test
+	 */
+	public function it_should_replace_the_featured_image_to_web_p_when_requesting_the_featured_image() {
+		$attachment_id = $this->factory->attachment->create_upload_object( TESTS_PLUGIN_DIR . '/tests/testdata/modules/images/paint.jpeg' );
+		$post_id       = $this->factory()->post->create();
+		set_post_thumbnail( $post_id, $attachment_id );
+
+		$featured_image = get_the_post_thumbnail( $post_id );
+
+		$this->assertTrue( has_post_thumbnail( $post_id ) );
+		$this->assertStringContainsString( '.webp', $featured_image );
+		$this->assertStringNotContainsString( '.jpeg', $featured_image );
+	}
 }