Simpler fix

Author: sirreal

src/wp-includes/html-api/class-wp-html-processor.php

@@ -1358,25 +1358,7 @@ public function serialize_token(): string {
 				break;
 
 			case '#text':
-				$text = $this->get_modifiable_text();
-				if ( WP_HTML_Tag_Processor::TEXT_IS_WHITESPACE === $this->text_node_classification ) {
-					$parent_node_name = $this->state->stack_of_open_elements->at( $this->state->stack_of_open_elements->count() - 1 )?->node_name;
-					if ( 'PRE' === $parent_node_name || 'LISTING' === $parent_node_name ) {
-						/*
-						 * DO NOT DO THIS
-						 * This case is exceptional and we must peek at processor internals.
-						 */
-						$newline_was_erased = Closure::bind(
-							fn () => $this->skip_newline_at === $this->token_starts_at,
-							$this,
-							WP_HTML_Tag_Processor::class
-						)();
-						if ( $newline_was_erased ) {
-							$text = "\n{$text}";
-						}
-					}
-				}
-				$html .= htmlspecialchars( $text, ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML5, 'UTF-8' );
+				$html .= htmlspecialchars( $this->get_modifiable_text(), ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML5, 'UTF-8' );
 				break;
 
 			// Unlike the `<>` which is interpreted as plaintext, this is ignored entirely.
@@ -1430,6 +1412,10 @@ public function serialize_token(): string {
 
 		$html .= '>';
 
+		if ( $tag_name === 'TEXTAREA' || $tag_name === 'PRE' || $tag_name === 'LISTING' ) {
+			$html .= "\n";
+		}
+
 		// Flush out self-contained elements.
 		if ( $in_html && in_array( $tag_name, array( 'IFRAME', 'NOEMBED', 'NOFRAMES', 'SCRIPT', 'STYLE', 'TEXTAREA', 'TITLE', 'XMP' ), true ) ) {
 			$text = $this->get_modifiable_text();
@@ -1445,19 +1431,6 @@ public function serialize_token(): string {
 				case 'STYLE':
 					break;
 
-				/*
-				 * Textarea elements ignore a leading newline. It is not present in `get_modifiable_text()`
-				 * because the HTML parser doesn't include it in the text node.
-				 * Serialization can always add a leading newline because it will be ignored by an
-				 * HTML parser.
-				 * This is especially important in case the text starts with a sequence of newlines.
-				 * If normalization removes a single leading newline, it would cause the
-				 * _significant_ following newline to be ignore by any later processing
-				 * or a browser.
-				 */
-				case 'TEXTAREA':
-					$text = "\n{$text}";
-					// Intentional fallthrough, TEXTAREA should have default handling.
 				default:
 					$text = htmlspecialchars( $text, ENT_QUOTES | ENT_SUBSTITUTE | ENT_HTML5, 'UTF-8' );
 			}