HTML API: Parse doctypes and set full parser quirks mode correctly

phpcs.xml.dist

@@ -262,6 +262,7 @@
 	     in the parsing, and distance the code from its standard. -->
 	<rule ref="Generic.PHP.DiscourageGoto.Found">
 		<exclude-pattern>/wp-includes/html-api/class-wp-html-processor\.php</exclude-pattern>
+		<exclude-pattern>/wp-includes/html-api/class-wp-html-tag-processor\.php</exclude-pattern>
 	</rule>
 
 	<!-- Exclude sample config from modernization to prevent breaking CI workflows based on WP-CLI scaffold.

src/wp-includes/html-api/class-wp-html-doctype-info.php

@@ -0,0 +1,269 @@
+<?php
+/**
+ * HTML API: WP_HTML_Doctype_Info class
+ *
+ * @package WordPress
+ * @subpackage HTML-API
+ * @since 6.7.0
+ */
+
+/**
+ * Core class used by the HTML API processor to represent a DOCTYPE declaration.
+ *
+ * @since 6.7.0
+ */
+class WP_HTML_Doctype_Info {
+	/**
+	 * The name of the DOCTYPE.
+	 *
+	 * @var string|null
+	 */
+	private $name;
+
+	/**
+	 * The public identifier of the DOCTYPE.
+	 *
+	 * @var string|null
+	 */
+	private $public_identifier;
+
+	/**
+	 * The system identifier of the DOCTYPE.
+	 *
+	 * @var string|null
+	 */
+	private $system_identifier;
+
+	/**
+	 * Whether the DOCTYPE token force-quirks flag is set.
+	 *
+	 * @var bool
+	 */
+	private $force_quirks_flag;
+
+	/**
+	 * Constructor.
+	 *
+	 * The arguments to this constructor correspond to the "DOCTYPE token" as defined in the
+	 * HTML specification.
+	 *
+	 * > DOCTYPE tokens have a name, a public identifier, a system identifier,
+	 * > and a force-quirks flag.
+	 *
+	 * @see https://html.spec.whatwg.org/multipage/parsing.html#tokenization
+	 *
+	 * @since 6.7.0
+	 *
+	 * @param string|null $name              The name of the DOCTYPE.
+	 * @param string|null $public_identifier The public identifier of the DOCTYPE.
+	 * @param string|null $system_identifier The system identifier of the DOCTYPE.
+	 * @param bool        $force_quirks_flag Whether the DOCTYPE token force-quirks flag is set.
+	 */
+	public function __construct(
+		?string $name,
+		?string $public_identifier,
+		?string $system_identifier,
+		bool $force_quirks_flag
+	) {
+		$this->name              = $name;
+		$this->public_identifier = $public_identifier;
+		$this->system_identifier = $system_identifier;
+		$this->force_quirks_flag = $force_quirks_flag;
+	}
+
+	/**
+	 * Gets the name of the DOCTYPE.
+	 *
+	 * @since 6.7.0
+	 *
+	 * @return string The name of the DOCTYPE.
+	 */
+	public function get_name(): string {
+		return $this->name ?? '';
+	}
+
+	/**
+	 * Gets the public identifier of the DOCTYPE.
+	 *
+	 * @since 6.7.0
+	 *
+	 * @return string The public identifier of the DOCTYPE.
+	 */
+	public function get_public_identifier(): string {
+		return $this->public_identifier ?? '';
+	}
+
+	/**
+	 * Gets the system identifier of the DOCTYPE.
+	 *
+	 * @since 6.7.0
+	 *
+	 * @return string The system identifier of the DOCTYPE.
+	 */
+	public function get_system_identifier(): string {
+		return $this->system_identifier ?? '';
+	}
+
+	/**
+	 * Determines the resulting document compatibility mode for this DOCTYPE.
+	 *
+	 * When a DOCTYPE appears in the appropriate place in a document, its contents determine
+	 * the compatibility mode of the document. This implements an algorithm described in the
+	 * HTML standard for handling a DOCTYPE token in the "initial" insertion mode.
+	 *
+	 * @see https://html.spec.whatwg.org/multipage/parsing.html#the-initial-insertion-mode
+	 *
+	 * @since 6.7.0
+	 *
+	 * @return string A string indicating the resulting quirks mode. One of "quirks",
+	 *                "limited-quirks", or "no-quirks".
+	 */
+	public function get_compatibility_mode(): string {
+		/*
+		 * > A system identifier whose value is the empty string is not considered missing for the
+		 * > purposes of the conditions above.
+		 */
+		$system_identifier_is_missing = null === $this->system_identifier;
+
+		/*
+		 * > The system identifier and public identifier strings must be compared to the values
+		 * > given in the lists above in an ASCII case-insensitive manner. A system identifier whose
+		 * > value is the empty string is not considered missing for the purposes of the conditions above.
+		 */
+		$public_identifier = null === $this->public_identifier ? '' : strtolower( $this->public_identifier );
+		$system_identifier = null === $this->system_identifier ? '' : strtolower( $this->system_identifier );
+
+		/*
+		 * > [If] the DOCTYPE token matches one of the conditions in the following list, then set
+		 * > the Document to quirks mode:
+		 */
+
+		// > The force-quirks flag is set to on.
+		if ( $this->force_quirks_flag ) {
+			return 'quirks';
+		}
+
+		// > The name is not "html".
+		if ( 'html' !== $this->name ) {
+			return 'quirks';
+		}
+
+		// > The public identifier is set to…
+		if (
+			'-//w3o//dtd w3 html strict 3.0//en//' === $public_identifier ||
+			'-/w3c/dtd html 4.0 transitional/en' === $public_identifier ||
+			'html' === $public_identifier
+		) {
+			return 'quirks';
+		}
+
+		// > The system identifier is set to…
+		if ( 'http://www.ibm.com/data/dtd/v11/ibmxhtml1-transitional.dtd' === $system_identifier ) {
+			return 'quirks';
+		}
+
+		/*
+		 * All of the following conditions depend on matching the public identifier.
+		 * If the public identifier is falsy, none of the following conditions will match.
+		 */
+		if ( '' === $public_identifier ) {
+			return 'no-quirks';
+		}
+
+		// > The public identifier starts with…
+		if (
+			str_starts_with( $public_identifier, '+//silmaril//dtd html pro v0r11 19970101//' ) ||
+			str_starts_with( $public_identifier, '-//as//dtd html 3.0 aswedit + extensions//' ) ||
+			str_starts_with( $public_identifier, '-//advasoft ltd//dtd html 3.0 aswedit + extensions//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.0 level 1//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.0 level 2//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.0 strict level 1//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.0 strict level 2//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.0 strict//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.0//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 2.1e//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 3.0//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 3.2 final//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 3.2//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html 3//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html level 0//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html level 1//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html level 2//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html level 3//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html strict level 0//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html strict level 1//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html strict level 2//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html strict level 3//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html strict//' ) ||
+			str_starts_with( $public_identifier, '-//ietf//dtd html//' ) ||
+			str_starts_with( $public_identifier, '-//metrius//dtd metrius presentational//' ) ||
+			str_starts_with( $public_identifier, '-//microsoft//dtd internet explorer 2.0 html strict//' ) ||
+			str_starts_with( $public_identifier, '-//microsoft//dtd internet explorer 2.0 html//' ) ||
+			str_starts_with( $public_identifier, '-//microsoft//dtd internet explorer 2.0 tables//' ) ||
+			str_starts_with( $public_identifier, '-//microsoft//dtd internet explorer 3.0 html strict//' ) ||
+			str_starts_with( $public_identifier, '-//microsoft//dtd internet explorer 3.0 html//' ) ||
+			str_starts_with( $public_identifier, '-//microsoft//dtd internet explorer 3.0 tables//' ) ||
+			str_starts_with( $public_identifier, '-//netscape comm. corp.//dtd html//' ) ||
+			str_starts_with( $public_identifier, '-//netscape comm. corp.//dtd strict html//' ) ||
+			str_starts_with( $public_identifier, "-//o'reilly and associates//dtd html 2.0//" ) ||
+			str_starts_with( $public_identifier, "-//o'reilly and associates//dtd html extended 1.0//" ) ||
+			str_starts_with( $public_identifier, "-//o'reilly and associates//dtd html extended relaxed 1.0//" ) ||
+			str_starts_with( $public_identifier, '-//sq//dtd html 2.0 hotmetal + extensions//' ) ||
+			str_starts_with( $public_identifier, '-//softquad software//dtd hotmetal pro 6.0::19990601::extensions to html 4.0//' ) ||
+			str_starts_with( $public_identifier, '-//softquad//dtd hotmetal pro 4.0::19971010::extensions to html 4.0//' ) ||
+			str_starts_with( $public_identifier, '-//spyglass//dtd html 2.0 extended//' ) ||
+			str_starts_with( $public_identifier, '-//sun microsystems corp.//dtd hotjava html//' ) ||
+			str_starts_with( $public_identifier, '-//sun microsystems corp.//dtd hotjava strict html//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 3 1995-03-24//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 3.2 draft//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 3.2 final//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 3.2//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 3.2s draft//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 4.0 frameset//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html 4.0 transitional//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html experimental 19960712//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd html experimental 970421//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd w3 html//' ) ||
+			str_starts_with( $public_identifier, '-//w3o//dtd w3 html 3.0//' ) ||
+			str_starts_with( $public_identifier, '-//webtechs//dtd mozilla html 2.0//' ) ||
+			str_starts_with( $public_identifier, '-//webtechs//dtd mozilla html//' )
+		) {
+			return 'quirks';
+		}
+
+		// > The system identifier is missing and the public identifier starts with…
+		if (
+			$system_identifier_is_missing && (
+				str_starts_with( $public_identifier, '-//w3c//dtd html 4.01 frameset//' ) ||
+				str_starts_with( $public_identifier, '-//w3c//dtd html 4.01 transitional//' )
+			)
+		) {
+			return 'quirks';
+		}
+
+		/*
+		 * > Otherwise, [if] the DOCTYPE token matches one of the conditions in
+		 * > the following list, then set the Document to limited-quirks mode.
+		 */
+
+		// > The public identifier starts with…
+		if (
+			str_starts_with( $public_identifier, '-//w3c//dtd xhtml 1.0 frameset//' ) ||
+			str_starts_with( $public_identifier, '-//w3c//dtd xhtml 1.0 transitional//' )
+		) {
+			return 'limited-quirks';
+		}
+
+		// > The system identifier is not missing and the public identifier starts with…
+		if (
+			! $system_identifier_is_missing && (
+				str_starts_with( $public_identifier, '-//w3c//dtd html 4.01 frameset//' ) ||
+				str_starts_with( $public_identifier, '-//w3c//dtd html 4.01 transitional//' )
+			)
+		) {
+			return 'limited-quirks';
+		}
+
+		return 'no-quirks';
+	}
+}

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

@@ -459,6 +459,24 @@ private function bail( string $message ) {
 		throw $this->unsupported_exception;
 	}
 
+	/**
+	 * Sets the document compatibility mode (quirks or no-quirks) based on a DOCTYPE declaration.
+	 *
+	 * @see https://html.spec.whatwg.org/multipage/parsing.html#parser-cannot-change-the-mode-flag
+	 *
+	 * @since 6.7.0
+	 */
+	private function update_document_mode_from_doctype(): void {
+		$doctype = $this->get_doctype_info();
+		if ( null === $doctype ) {
+			return;
+		}
+
+		if ( 'quirks' === $doctype->get_compatibility_mode() ) {
+			$this->state->document_mode = WP_HTML_Processor_State::QUIRKS_MODE;
+		}
+	}
+
 	/**
 	 * Returns the last error, if any.
 	 *
@@ -1076,19 +1094,12 @@ private function step_initial(): bool {
 			 * > A DOCTYPE token
 			 */
 			case 'html':
-				$contents = $this->get_modifiable_text();
-				if ( ' html' !== $contents ) {
-					/*
-					 * @todo When the HTML Tag Processor fully parses the DOCTYPE declaration,
-					 *       this code should examine the contents to set the compatability mode.
-					 */
-					$this->bail( 'Cannot process any DOCTYPE other than a normative HTML5 doctype.' );
-				}
-
+				$this->update_document_mode_from_doctype();
 				/*
 				 * > Then, switch the insertion mode to "before html".
 				 */
 				$this->state->insertion_mode = WP_HTML_Processor_State::INSERTION_MODE_BEFORE_HTML;
+				$this->insert_html_element( $this->state->current_token );
 				return true;
 		}