Adapt tree-shaker to keep CSS that is targeted by toggles

includes/sanitizers/class-amp-core-theme-sanitizer.php

@@ -977,11 +977,9 @@ static function() use ( $args ) {
 				<?php endif; ?>
 
 				<?php if ( 'twentytwenty' === get_template() ) : ?>
-					.cover-modal,
-					.active {
+					.cover-modal {
 						display: inherit;
 					}
-				}
 				<?php elseif ( 'twentyseventeen' === get_template() ) : ?>
 					/* Show the button*/
 					.no-js .menu-toggle {

includes/sanitizers/class-amp-style-sanitizer.php

@@ -456,8 +456,30 @@ private function get_used_class_names() {
 			$classes .= ' ' . $class_attribute->nodeValue;
 		}
 
-		// Find all [class] attributes and capture the contents of any single- or double-quoted strings.
+		// Find all [class] attributes and capture the contents of any single- or double-quoted strings,
+		// as well as <amp-state> content that might be used.
 		foreach ( $this->xpath->query( '//*/@' . AMP_DOM_Utils::AMP_BIND_DATA_ATTR_PREFIX . 'class' ) as $bound_class_attribute ) {
+			if ( preg_match_all( '/([a-zA-Z0-9_]+?)\[\s*([\'"])([^\2]*?)\2\s*\]/', $bound_class_attribute->nodeValue, $matches ) ) {
+				$amp_states = $matches[1];
+				$properties = $matches[3];
+
+				foreach ( $amp_states as $index => $amp_state ) {
+					$state_element = $this->xpath->query( "//amp-state[@id = '{$amp_state}' ]/script" )->item( 0 );
+
+					if ( ! $state_element ) {
+						continue;
+					}
+
+					$state_data = json_decode( $state_element->textContent, true );
+
+					if ( isset( $state_data[ $properties[ $index ] ] ) ) {
+						$classes .= ' ' . $state_data[ $properties[ $index ] ];
+					}
+				}
+
+				continue;
+			}
+
 			if ( preg_match_all( '/([\'"])([^\1]*?)\1/', $bound_class_attribute->nodeValue, $matches ) ) {
 				$classes .= ' ' . implode( ' ', $matches[2] );
 			}