HTML API: Add support for IN SELECT IN TABLE parsing.

As part of work to add more spec support to the HTML API, this patch adds
support for the IN SELECT IN TABLE insertion mode. This small section of the
spec handles rules for the `<select>` element and its children when found
inside of a `<table>`.

Developed in #7044
Discussed in https://core.trac.wordpress.org/ticket/61576

Props: dmsnell, jonsurrell.
See #61576.


git-svn-id: https://develop.svn.wordpress.org/trunk@58841 602fd350-edb4-49c9-b593-d223f7449a82

Author: dmsnell

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

@@ -3771,7 +3771,7 @@ private function step_in_select(): bool {
 	 * This internal function performs the 'in select in table' insertion mode
 	 * logic for the generalized WP_HTML_Processor::step() function.
 	 *
-	 * @since 6.7.0 Stub implementation.
+	 * @since 6.7.0
 	 *
 	 * @throws WP_HTML_Unsupported_Exception When encountering unsupported HTML input.
 	 *
@@ -3781,7 +3781,52 @@ private function step_in_select(): bool {
 	 * @return bool Whether an element was found.
 	 */
 	private function step_in_select_in_table(): bool {
-		$this->bail( 'No support for parsing in the ' . WP_HTML_Processor_State::INSERTION_MODE_IN_SELECT_IN_TABLE . ' state.' );
+		$token_name = $this->get_token_name();
+		$token_type = $this->get_token_type();
+		$op_sigil   = '#tag' === $token_type ? ( parent::is_tag_closer() ? '-' : '+' ) : '';
+		$op         = "{$op_sigil}{$token_name}";
+
+		switch ( $op ) {
+			/*
+			 * > A start tag whose tag name is one of: "caption", "table", "tbody", "tfoot", "thead", "tr", "td", "th"
+			 */
+			case '+CAPTION':
+			case '+TABLE':
+			case '+TBODY':
+			case '+TFOOT':
+			case '+THEAD':
+			case '+TR':
+			case '+TD':
+			case '+TH':
+				// @todo Indicate a parse error once it's possible.
+				$this->state->stack_of_open_elements->pop_until( 'SELECT' );
+				$this->reset_insertion_mode();
+				return $this->step( self::REPROCESS_CURRENT_NODE );
+
+			/*
+			 * > An end tag whose tag name is one of: "caption", "table", "tbody", "tfoot", "thead", "tr", "td", "th"
+			 */
+			case '-CAPTION':
+			case '-TABLE':
+			case '-TBODY':
+			case '-TFOOT':
+			case '-THEAD':
+			case '-TR':
+			case '-TD':
+			case '-TH':
+				// @todo Indicate a parse error once it's possible.
+				if ( ! $this->state->stack_of_open_elements->has_element_in_table_scope( $token_name ) ) {
+					return $this->step();
+				}
+				$this->state->stack_of_open_elements->pop_until( 'SELECT' );
+				$this->reset_insertion_mode();
+				return $this->step( self::REPROCESS_CURRENT_NODE );
+		}
+
+		/*
+		 * > Anything else
+		 */
+		return $this->step_in_select();
 	}
 
 	/**