Handle omission of classic-theme-styles

Author: westonruter

src/wp-includes/script-loader.php

@@ -3907,13 +3907,14 @@ public function remove() {
 				$inserted_after            = $printed_core_block_styles;
 				$printed_core_block_styles = '';
 
-				if ( ! $processor->has_bookmark( 'last_style_at_enqueued_block_assets' ) ) {
-					// TODO: There is no coverage for this.
-					$inserted_after .= $printed_other_block_styles;
-					$inserted_after .= $printed_global_styles;
-
+				if ( ! $processor->has_bookmark( 'classic_theme_styles' ) ) {
+					$inserted_after            .= "\n" . $printed_other_block_styles;
 					$printed_other_block_styles = '';
-					$printed_global_styles      = '';
+
+					if ( ! $processor->has_bookmark( 'last_style_at_enqueued_block_assets' ) ) {
+						$inserted_after       .= "\n" . $printed_global_styles;
+						$printed_global_styles = '';
+					}
 				}
 
 				if ( '' !== $inserted_after ) {
@@ -3923,8 +3924,14 @@ public function remove() {
 
 			if ( '' !== $printed_global_styles && $processor->has_bookmark( 'last_style_at_enqueued_block_assets' ) ) {
 				$processor->seek( 'last_style_at_enqueued_block_assets' );
+
 				$processor->insert_after( "\n" . $printed_global_styles );
 				$printed_global_styles = '';
+
+				if ( ! $processor->has_bookmark( 'classic_theme_styles' ) ) {
+					$processor->insert_after( "\n" . $printed_other_block_styles );
+					$printed_other_block_styles = '';
+				}
 			}
 
 			if ( '' !== $printed_other_block_styles && $processor->has_bookmark( 'classic_theme_styles' ) ) {

tests/phpunit/tests/template.php

@@ -1549,6 +1549,39 @@ public function data_wp_hoist_late_printed_styles(): array {
 					'BODY' => array(),
 				),
 			),
+			'classic_theme_styles_omitted'                => array(
+				'set_up'            => static function () {
+					// Note that wp_enqueue_scripts is used instead of enqueue_block_assets because it runs again at the former action.
+					add_action(
+						'wp_enqueue_scripts',
+						static function () {
+							wp_dequeue_style( 'classic-theme-styles' );
+						},
+						100
+					);
+				},
+				'inline_size_limit' => PHP_INT_MAX,
+				'expected_styles'   => array(
+					'HEAD' => array(
+						'wp-img-auto-sizes-contain-inline-css',
+						'early-css',
+						'early-inline-css',
+						'wp-emoji-styles-inline-css',
+						'wp-block-library-inline-css',
+						'wp-block-separator-inline-css',
+						'third-party-test-block-css',
+						'custom-block-styles-css',
+						'global-styles-inline-css',
+						'normal-css',
+						'normal-inline-css',
+						'wp-custom-css',
+						'late-css',
+						'late-inline-css',
+						'core-block-supports-inline-css',
+					),
+					'BODY' => array(),
+				),
+			),
 			'standard_classic_theme_config_extra_block_library_inline_style' => array(
 				'set_up'            => static function () {
 					add_action(