General: Remove support for IE conditional comments.

Remove the ability to enqueue scripts and styles wrapped in IE conditional comment tags. Conditional comment support was removed from IE in version 10 in 2012, and no core supported browser renders them in any way. IE9 has global usage approaching zero. WordPress dropped support for IE10 and below in version 4.8.

Patch adds a deprecation notice if the conditional data argument is added. Scripts and styles are not printed, and neither are their dependencies if they are not required by other non-conditional scripts. Conditional dependencies are removed from core enqueues. 

Props jonsurrell, joedolson, shailu25, siliconforks, dmsnell, sabernhardt, rollybueno.
Fixes #63821.

git-svn-id: https://develop.svn.wordpress.org/trunk@60948 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/js/_enqueues/vendor/json2.js

@@ -289,6 +289,13 @@ public function add_data( $handle, $key, $value ) {
 		if ( ! isset( $this->registered[ $handle ] ) ) {
 			return false;
 		}
+		if ( 'conditional' === $key && '_required-conditional-dependency_' !== $value ) {
+			_deprecated_argument(
+				'WP_Dependencies->add_data()',
+				'6.9.0',
+				__( 'IE conditional comments are ignored by all supported browsers.' )
+			);
+		}
 
 		return $this->registered[ $handle ]->add_data( $key, $value );
 	}

src/wp-includes/class-wp-dependencies.php

@@ -292,6 +292,9 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		$obj = $this->registered[ $handle ];
+		if ( $obj->extra['conditional'] ?? false ) {
+			return false;
+		}
 
 		if ( null === $obj->ver ) {
 			$ver = '';
@@ -303,12 +306,9 @@ public function do_item( $handle, $group = false ) {
 			$ver = $ver ? $ver . '&' . $this->args[ $handle ] : $this->args[ $handle ];
 		}
 
-		$src                   = $obj->src;
-		$strategy              = $this->get_eligible_loading_strategy( $handle );
-		$intended_strategy     = (string) $this->get_data( $handle, 'strategy' );
-		$ie_conditional_prefix = '';
-		$ie_conditional_suffix = '';
-		$conditional           = isset( $obj->extra['conditional'] ) ? $obj->extra['conditional'] : '';
+		$src               = $obj->src;
+		$strategy          = $this->get_eligible_loading_strategy( $handle );
+		$intended_strategy = (string) $this->get_data( $handle, 'strategy' );
 
 		if ( ! $this->is_delayed_strategy( $intended_strategy ) ) {
 			$intended_strategy = '';
@@ -333,16 +333,11 @@ public function do_item( $handle, $group = false ) {
 			return false;
 		}
 
-		if ( $conditional ) {
-			$ie_conditional_prefix = "<!--[if {$conditional}]>\n";
-			$ie_conditional_suffix = "<![endif]-->\n";
-		}
-
 		$before_script = $this->get_inline_script_tag( $handle, 'before' );
 		$after_script  = $this->get_inline_script_tag( $handle, 'after' );
 
 		if ( $before_script || $after_script ) {
-			$inline_script_tag = $ie_conditional_prefix . $before_script . $after_script . $ie_conditional_suffix;
+			$inline_script_tag = $before_script . $after_script;
 		} else {
 			$inline_script_tag = '';
 		}
@@ -378,7 +373,7 @@ public function do_item( $handle, $group = false ) {
 				// Have to print the so-far concatenated scripts right away to maintain the right order.
 				_print_scripts();
 				$this->reset();
-			} elseif ( $this->in_default_dir( $filtered_src ) && ! $conditional ) {
+			} elseif ( $this->in_default_dir( $filtered_src ) ) {
 				$this->print_code     .= $this->print_extra_script( $handle, false );
 				$this->concat         .= "$handle,";
 				$this->concat_version .= "$handle$ver";
@@ -389,18 +384,8 @@ public function do_item( $handle, $group = false ) {
 			}
 		}
 
-		$has_conditional_data = $conditional && $this->get_data( $handle, 'data' );
-
-		if ( $has_conditional_data ) {
-			echo $ie_conditional_prefix;
-		}
-
 		$this->print_extra_script( $handle );
 
-		if ( $has_conditional_data ) {
-			echo $ie_conditional_suffix;
-		}
-
 		// A single item may alias a set of items, by having dependencies, but no source.
 		if ( ! $src ) {
 			if ( $inline_script_tag ) {
@@ -453,13 +438,14 @@ public function do_item( $handle, $group = false ) {
 		if ( is_string( $actual_fetchpriority ) && 'auto' !== $actual_fetchpriority ) {
 			$attr['fetchpriority'] = $actual_fetchpriority;
 		}
+
 		if ( $original_fetchpriority !== $actual_fetchpriority ) {
 			$attr['data-wp-fetchpriority'] = $original_fetchpriority;
 		}
 
-		$tag  = $translations . $ie_conditional_prefix . $before_script;
+		$tag  = $translations . $before_script;
 		$tag .= wp_get_script_tag( $attr );
-		$tag .= $after_script . $ie_conditional_suffix;
+		$tag .= $after_script;
 
 		/**
 		 * Filters the HTML script tag of an enqueued script.
@@ -851,6 +837,11 @@ public function add_data( $handle, $key, $value ) {
 			return false;
 		}
 
+		if ( 'conditional' === $key ) {
+			// If a dependency is declared by a conditional script, remove it.
+			$this->registered[ $handle ]->deps = array();
+		}
+
 		if ( 'strategy' === $key ) {
 			if ( ! empty( $value ) && ! $this->is_delayed_strategy( $value ) ) {
 				_doing_it_wrong(

src/wp-includes/class-wp-scripts.php

@@ -154,7 +154,10 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		$obj = $this->registered[ $handle ];
+		if ( $obj->extra['conditional'] ?? false ) {
 
+			return false;
+		}
 		if ( null === $obj->ver ) {
 			$ver = '';
 		} else {
@@ -165,16 +168,7 @@ public function do_item( $handle, $group = false ) {
 			$ver = $ver ? $ver . '&' . $this->args[ $handle ] : $this->args[ $handle ];
 		}
 
-		$src                   = $obj->src;
-		$ie_conditional_prefix = '';
-		$ie_conditional_suffix = '';
-		$conditional           = isset( $obj->extra['conditional'] ) ? $obj->extra['conditional'] : '';
-
-		if ( $conditional ) {
-			$ie_conditional_prefix = "<!--[if {$conditional}]>\n";
-			$ie_conditional_suffix = "<![endif]-->\n";
-		}
-
+		$src          = $obj->src;
 		$inline_style = $this->print_inline_style( $handle, false );
 
 		if ( $inline_style ) {
@@ -189,7 +183,7 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		if ( $this->do_concat ) {
-			if ( $this->in_default_dir( $src ) && ! $conditional && ! isset( $obj->extra['alt'] ) ) {
+			if ( $this->in_default_dir( $src ) && ! isset( $obj->extra['alt'] ) ) {
 				$this->concat         .= "$handle,";
 				$this->concat_version .= "$handle$ver";
 
@@ -279,17 +273,13 @@ public function do_item( $handle, $group = false ) {
 		}
 
 		if ( $this->do_concat ) {
-			$this->print_html .= $ie_conditional_prefix;
 			$this->print_html .= $tag;
 			if ( $inline_style_tag ) {
 				$this->print_html .= $inline_style_tag;
 			}
-			$this->print_html .= $ie_conditional_suffix;
 		} else {
-			echo $ie_conditional_prefix;
 			echo $tag;
 			$this->print_inline_style( $handle );
-			echo $ie_conditional_suffix;
 		}
 
 		return true;
@@ -373,6 +363,28 @@ public function print_inline_style( $handle, $display = true ) {
 		return true;
 	}
 
+	/**
+	 * Overrides the add_data method from WP_Dependencies, to allow unsetting dependencies for conditional styles.
+	 *
+	 * @since 6.9.0
+	 *
+	 * @param string $handle Name of the item. Should be unique.
+	 * @param string $key    The data key.
+	 * @param mixed  $value  The data value.
+	 * @return bool True on success, false on failure.
+	 */
+	public function add_data( $handle, $key, $value ) {
+		if ( ! isset( $this->registered[ $handle ] ) ) {
+			return false;
+		}
+
+		if ( 'conditional' === $key ) {
+			$this->registered[ $handle ]->deps = array();
+		}
+
+		return parent::add_data( $handle, $key, $value );
+	}
+
 	/**
 	 * Determines style dependencies.
 	 *

src/wp-includes/class-wp-styles.php

@@ -1,19 +1 @@
-.dashicons-no {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAQAAAAngNWGAAAAcElEQVR4AdXRVxmEMBAGwJMQCUhAIhKQECmRsFJwMFfp7HfP/E8pk0173CuKpt/0R+WaBaaZqogLagBMuh+DdoKbyRCwqZ/SnM0R5oQuZ2UHS8Z6k23qPxZCTrV5UlHMi8bsfHVXP7K/GXZHaTO7S54CWLdHlN2YIwAAAABJRU5ErkJggg==);
-}
-
-.dashicons-admin-comments {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAATUlEQVR4AWMYWqCpvUcAiA8A8X9iMFStAD4DG0AKScQNVDZw1MBRAwvIMLCA5jmFlCD4AMQGlOTtBgoNwzQQ3TCKDaTcMMxYN2AYVgAAYPKsEBxN0PIAAAAASUVORK5CYII=);
-}
-
-.wp-embed-comments a:hover .dashicons-admin-comments {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAATElEQVR4AWMYYqB4lQAQHwDi/8RgqFoBfAY2gBSSiBuobOCogaMGFpBhYAEdcwrhIPgAxAaU5O0GCg3DNBDdMIoNpNwwzFg3YBhWAABG71qAFYcFqgAAAABJRU5ErkJggg==);
-}
-
-.dashicons-share {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAc0lEQVR4AWMYfqCpvccAiBcA8X8gfgDEBZQaeAFkGBoOoMR1/7HgDeQa2ECZgQiDHID4AMwAor0MCmBoQP+HBnwAskFQdgBRkQJViGk7wiAHUr21AYdhDTA1dDOQHl6mPFLokmwoT9j0z3qUFw70L77oDwAiuzCIub1XpQAAAABJRU5ErkJggg==);
-}
-
-.wp-embed-share-dialog-open:hover .dashicons-share {
-	background-image: url(data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABQAAAAUCAYAAACNiR0NAAAAc0lEQVR4AWMYhqB4lQEQLwDi/0D8AIgLKDXwAsgwNBxAiev+Y8EbyDWwgTIDEQY5APEBmAFEexkUwNCA/g8N+ABkg6DsAKIiBaoQ03aEQQ6kemsDDsMaYEroZiA9vEx5pNAl2VCesOmf9SgvHOhffNEfAAAMqPR5IEZH5wAAAABJRU5ErkJggg==);
-}
+/* Deprecated in WordPress 6.9 */

src/wp-includes/css/wp-embed-template-ie.css

@@ -1056,7 +1056,6 @@ function wp_embed_excerpt_attachment( $content ) {
  * @since 4.4.0
  */
 function enqueue_embed_scripts() {
-	wp_enqueue_style( 'wp-embed-template-ie' );
 
 	/**
 	 * Fires when scripts and styles are enqueued for the embed iframe.

src/wp-includes/embed.php

@@ -435,9 +435,10 @@ function wp_script_is( $handle, $status = 'enqueued' ) {
  * Works only if the script has already been registered.
  *
  * Possible values for $key and $value:
- * 'conditional' string Comments for IE 6, lte IE 7, etc.
+ * 'strategy' string 'defer' or 'async'.
  *
  * @since 4.2.0
+ * @since 6.9.0 Updated possible values to remove reference to 'conditional' and add 'strategy'.
  *
  * @see WP_Dependencies::add_data()
  *

src/wp-includes/functions.wp-scripts.php

@@ -220,7 +220,6 @@ function wp_style_is( $handle, $status = 'enqueued' ) {
  * Works only if the stylesheet has already been registered.
  *
  * Possible values for $key and $value:
- * 'conditional' string      Comments for IE 6, lte IE 7 etc.
  * 'rtl'         bool|string To declare an RTL stylesheet.
  * 'suffix'      string      Optional suffix, used in combination with RTL.
  * 'alt'         bool        For rel="alternate stylesheet".
@@ -233,10 +232,12 @@ function wp_style_is( $handle, $status = 'enqueued' ) {
  * @since 3.6.0
  * @since 5.8.0 Added 'path' as an official value for $key.
  *              See {@see wp_maybe_inline_styles()}.
+ * @since 6.9.0 'conditional' value changed. If the 'conditional' parameter is present
+ *              the stylesheet will be ignored.
  *
  * @param string $handle Name of the stylesheet.
  * @param string $key    Name of data point for which we're storing a value.
- *                       Accepts 'conditional', 'rtl' and 'suffix', 'alt', 'title' and 'path'.
+ *                       Accepts 'rtl' and 'suffix', 'alt', 'title' and 'path'.
  * @param mixed  $value  String containing the CSS data to be added.
  * @return bool True on success, false on failure.
  */

src/wp-includes/functions.wp-styles.php

@@ -1043,7 +1043,7 @@ function wp_default_scripts( $scripts ) {
 	$scripts->add( 'plupload-handlers', "/wp-includes/js/plupload/handlers$suffix.js", array( 'clipboard', 'jquery', 'plupload', 'underscore', 'wp-a11y', 'wp-i18n' ) );
 	did_action( 'init' ) && $scripts->localize( 'plupload-handlers', 'pluploadL10n', $uploader_l10n );
 
-	$scripts->add( 'wp-plupload', "/wp-includes/js/plupload/wp-plupload$suffix.js", array( 'plupload', 'jquery', 'json2', 'media-models' ), false, 1 );
+	$scripts->add( 'wp-plupload', "/wp-includes/js/plupload/wp-plupload$suffix.js", array( 'plupload', 'jquery', 'media-models' ), false, 1 );
 	did_action( 'init' ) && $scripts->localize( 'wp-plupload', 'pluploadL10n', $uploader_l10n );
 
 	$scripts->add( 'comment-reply', "/wp-includes/js/comment-reply$suffix.js", array(), false, 1 );
@@ -1052,8 +1052,9 @@ function wp_default_scripts( $scripts ) {
 		$scripts->add_data( 'comment-reply', 'fetchpriority', 'low' ); // In Chrome this is automatically low due to the async strategy, but in Firefox and Safari the priority is normal/medium.
 	}
 
+	// Not used in core, obsolete. Registered for backward compatibility.
 	$scripts->add( 'json2', "/wp-includes/js/json2$suffix.js", array(), '2015-05-03' );
-	did_action( 'init' ) && $scripts->add_data( 'json2', 'conditional', 'lt IE 8' );
+	did_action( 'init' ) && $scripts->add_data( 'json2', 'conditional', '_required-conditional-dependency_' );
 
 	$scripts->add( 'underscore', "/wp-includes/js/underscore$dev_suffix.js", array(), '1.13.7', 1 );
 	$scripts->add( 'backbone', "/wp-includes/js/backbone$dev_suffix.js", array( 'underscore', 'jquery' ), '1.6.0', 1 );
@@ -1284,7 +1285,7 @@ function wp_default_scripts( $scripts ) {
 	// JS-only version of hoverintent (no dependencies).
 	$scripts->add( 'hoverintent-js', '/wp-includes/js/hoverintent-js.min.js', array(), '2.2.1', 1 );
 
-	$scripts->add( 'customize-base', "/wp-includes/js/customize-base$suffix.js", array( 'jquery', 'json2', 'underscore' ), false, 1 );
+	$scripts->add( 'customize-base', "/wp-includes/js/customize-base$suffix.js", array( 'jquery', 'underscore' ), false, 1 );
 	$scripts->add( 'customize-loader', "/wp-includes/js/customize-loader$suffix.js", array( 'customize-base' ), false, 1 );
 	$scripts->add( 'customize-preview', "/wp-includes/js/customize-preview$suffix.js", array( 'wp-a11y', 'customize-base' ), false, 1 );
 	$scripts->add( 'customize-models', '/wp-includes/js/customize-models.js', array( 'underscore', 'backbone' ), false, 1 );
@@ -1504,7 +1505,7 @@ function wp_default_scripts( $scripts ) {
 		$scripts->add( 'media', "/wp-admin/js/media$suffix.js", array( 'jquery', 'clipboard', 'wp-i18n', 'wp-a11y' ), false, 1 );
 		$scripts->set_translations( 'media' );
 
-		$scripts->add( 'image-edit', "/wp-admin/js/image-edit$suffix.js", array( 'jquery', 'jquery-ui-core', 'json2', 'imgareaselect', 'wp-a11y' ), false, 1 );
+		$scripts->add( 'image-edit', "/wp-admin/js/image-edit$suffix.js", array( 'jquery', 'jquery-ui-core', 'imgareaselect', 'wp-a11y' ), false, 1 );
 		$scripts->set_translations( 'image-edit' );
 
 		$scripts->add( 'set-post-thumbnail', "/wp-admin/js/set-post-thumbnail$suffix.js", array( 'jquery' ), false, 1 );
@@ -1514,7 +1515,7 @@ function wp_default_scripts( $scripts ) {
 		 * Navigation Menus: Adding underscore as a dependency to utilize _.debounce
 		 * see https://core.trac.wordpress.org/ticket/42321
 		 */
-		$scripts->add( 'nav-menu', "/wp-admin/js/nav-menu$suffix.js", array( 'jquery-ui-sortable', 'jquery-ui-draggable', 'jquery-ui-droppable', 'wp-lists', 'postbox', 'json2', 'underscore' ) );
+		$scripts->add( 'nav-menu', "/wp-admin/js/nav-menu$suffix.js", array( 'jquery-ui-sortable', 'jquery-ui-draggable', 'jquery-ui-droppable', 'wp-lists', 'postbox', 'underscore' ) );
 		$scripts->set_translations( 'nav-menu' );
 
 		$scripts->add( 'custom-header', '/wp-admin/js/custom-header.js', array( 'jquery-masonry' ), false, 1 );
@@ -1646,9 +1647,7 @@ function wp_default_styles( $styles ) {
 	$styles->add( 'media-views', "/wp-includes/css/media-views$suffix.css", array( 'buttons', 'dashicons', 'wp-mediaelement' ) );
 	$styles->add( 'wp-pointer', "/wp-includes/css/wp-pointer$suffix.css", array( 'dashicons' ) );
 	$styles->add( 'customize-preview', "/wp-includes/css/customize-preview$suffix.css", array( 'dashicons' ) );
-	$styles->add( 'wp-embed-template-ie', "/wp-includes/css/wp-embed-template-ie$suffix.css" );
 	$styles->add( 'wp-empty-template-alert', "/wp-includes/css/wp-empty-template-alert$suffix.css" );
-	$styles->add_data( 'wp-embed-template-ie', 'conditional', 'lte IE 8' );
 
 	// External libraries and friends.
 	$styles->add( 'imgareaselect', '/wp-includes/js/imgareaselect/imgareaselect.css', array(), '0.9.8' );
@@ -1664,6 +1663,8 @@ function wp_default_styles( $styles ) {
 	$styles->add( 'jcrop', '/wp-includes/js/jcrop/jquery.Jcrop.min.css', array(), '0.9.15' );
 	$styles->add( 'colors-fresh', false, array( 'wp-admin', 'buttons' ) ); // Old handle.
 	$styles->add( 'open-sans', $open_sans_font_url ); // No longer used in core as of 4.6.
+	$styles->add( 'wp-embed-template-ie', false );
+	$styles->add_data( 'wp-embed-template-ie', 'conditional', '_required-conditional-dependency_' );
 
 	// Noto Serif is no longer used by core, but may be relied upon by themes and plugins.
 	$fonts_url = '';