Implement text placeholder extraction in compile()

Parse funky comments (</%name>) to extract text placeholders. Store
each placeholder's offsets (start position and length) and context.
Repeated placeholders are captured as multiple offset entries.

Author: sirreal

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

@@ -48,13 +48,69 @@ public function get_placeholders(): array {
 	/**
 	 * Compiles the template to extract placeholder metadata.
 	 *
+	 * Parses the template once and caches placeholder positions, lengths,
+	 * and contexts. If a placeholder appears in both text and attribute
+	 * contexts, the attribute context takes precedence (more restrictive).
+	 *
 	 * @since 7.0.0
 	 */
 	private function compile(): void {
 		if ( null !== $this->compiled ) {
 			return;
 		}
+
 		$this->compiled = array();
+
+		$processor = new class( $this->template_string ) extends WP_HTML_Tag_Processor {
+			public function get_html(): string {
+				return $this->html;
+			}
+
+			public function get_bookmark( string $name ) {
+				return $this->bookmarks[ $name ] ?? null;
+			}
+
+			public function get_tag_attributes(): array {
+				return $this->attributes;
+			}
+		};
+
+		while ( $processor->next_token() ) {
+			switch ( $processor->get_token_type() ) {
+				case '#funky-comment':
+					$processor->set_bookmark( 'placeholder' );
+					$mark = $processor->get_bookmark( 'placeholder' );
+					if ( null === $mark ) {
+						break;
+					}
+
+					$start  = $mark->start;
+					$length = $mark->length;
+					$html   = $processor->get_html();
+
+					// Must be at least `</%x>` (5 chars) and start with `</%`
+					if ( $length < 5 || '%' !== $html[ $start + 2 ] ) {
+						break;
+					}
+
+					$placeholder = trim( substr( $html, $start + 3, $length - 4 ), " \t\n\r\f" );
+
+					// Valid placeholders match `/[a-z0-9_-]+/i`
+					if ( strlen( $placeholder ) !== strspn( $placeholder, 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_-' ) ) {
+						break;
+					}
+
+					if ( ! isset( $this->compiled[ $placeholder ] ) ) {
+						$this->compiled[ $placeholder ] = array(
+							'offsets' => array(),
+							'context' => 'text',
+						);
+					}
+
+					$this->compiled[ $placeholder ]['offsets'][] = array( $start, $length );
+					break;
+			}
+		}
 	}
 
 	private function __construct( string $template_string, array $replacements ) {

tests/phpunit/tests/html-api/wpHtmlTemplate.php

@@ -772,4 +772,41 @@ public function test_get_placeholders_returns_metadata() {
 		$this->assertSame( 'attribute', $placeholders['class']['context'] );
 		$this->assertSame( 'text', $placeholders['content']['context'] );
 	}
+
+	/**
+	 * Verifies text placeholders are extracted with correct offsets.
+	 *
+	 * @ticket 60229
+	 *
+	 * @covers ::get_placeholders
+	 */
+	public function test_extracts_text_placeholders_with_offsets() {
+		$template = T::from( '<p></%name></p>' );
+
+		$placeholders = $template->get_placeholders();
+
+		$this->assertArrayHasKey( 'name', $placeholders );
+		$this->assertSame( 'text', $placeholders['name']['context'] );
+		$this->assertCount( 1, $placeholders['name']['offsets'] );
+		// <p> is 3 chars, so </%name> starts at offset 3
+		$this->assertSame( 3, $placeholders['name']['offsets'][0][0] );
+		// </%name> is 8 chars
+		$this->assertSame( 8, $placeholders['name']['offsets'][0][1] );
+	}
+
+	/**
+	 * Verifies repeated text placeholders are captured.
+	 *
+	 * @ticket 60229
+	 *
+	 * @covers ::get_placeholders
+	 */
+	public function test_extracts_repeated_text_placeholders() {
+		$template = T::from( '<p></%name> and </%name></p>' );
+
+		$placeholders = $template->get_placeholders();
+
+		$this->assertArrayHasKey( 'name', $placeholders );
+		$this->assertCount( 2, $placeholders['name']['offsets'] );
+	}
 }