class-wp-rest-global-styles-controller-gutenberg.php in Gutenberg 23.2.0, at lib/class-wp-rest-global-styles-controller-gutenberg.php

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1	<?php
2	/**
3	* REST API: Bundle WP_Theme_JSON class instead of inheriting per WordPress version class
4	*
5	* Changes to this class should be synced to the corresponding class
6	* in WordPress core: src/wp-includes/rest-api/endpoints/class-wp-rest-global-styles-controller.php.
7	*
8	* @package gutenberg
9	* @subpackage REST_API
10	* @since 5.9.0
11	*/
12
13	/**
14	* Base Global Styles REST API Controller.
15	*/
16	class WP_REST_Global_Styles_Controller_Gutenberg extends WP_REST_Posts_Controller {
17
18	/**
19	* Whether the controller supports batching.
20	*
21	* @since 6.6.0
22	* @var array
23	*/
24	protected $allow_batch = array( 'v1' => false );
25
26	/**
27	* Constructor.
28	*
29	* @since 5.9.0
30	*/
31	/**
32	* Constructor.
33	*
34	* @since 6.6.0
35	*
36	* @param string $post_type Post type.
37	*/
38	public function __construct( $post_type = 'wp_global_styles' ) {
39	parent::__construct( $post_type );
40	}
41
42	/**
43	* Registers the controllers routes.
44	*
45	* @since 5.9.0
46	*/
47	public function register_routes() {
48	register_rest_route(
49	$this->namespace,
50	'/' . $this->rest_base . '/themes/(?P<stylesheet>[\/\s%\w\.\[\]\@_\-]+)/variations',
51	array(
52	array(
53	'methods' => WP_REST_Server::READABLE,
54	'callback' => array( $this, 'get_theme_items' ),
55	'permission_callback' => array( $this, 'get_theme_items_permissions_check' ),
56	'args' => array(
57	'stylesheet' => array(
58	'description' => __( 'The theme identifier', 'gutenberg' ),
59	'type' => 'string',
60	),
61	),
62	'allow_batch' => $this->allow_batch,
63	),
64	),
65	/*
66	* $override is set to true to avoid conflicts with the core endpoint.
67	* Do not sync to WordPress core.
68	*/
69	true
70	);
71
72	// List themes global styles.
73	register_rest_route(
74	$this->namespace,
75	// The route.
76	sprintf(
77	'/%s/themes/(?P<stylesheet>%s)',
78	$this->rest_base,
79	/*
80	* Matches theme's directory: `/themes/<subdirectory>/<theme>/` or `/themes/<theme>/`.
81	* Excludes invalid directory name characters: `/:<>*?"\|`.
82	*/
83	'[^\/:<>\\?"\\|]+(?:\/[^\/:<>\\?"\\|]+)?'
84	),
85	array(
86	array(
87	'methods' => WP_REST_Server::READABLE,
88	'callback' => array( $this, 'get_theme_item' ),
89	'permission_callback' => array( $this, 'get_theme_item_permissions_check' ),
90	'args' => array(
91	'stylesheet' => array(
92	'description' => __( 'The theme identifier', 'gutenberg' ),
93	'type' => 'string',
94	'sanitize_callback' => array( $this, '_sanitize_global_styles_callback' ),
95	),
96	),
97	'allow_batch' => $this->allow_batch,
98	),
99	),
100	/*
101	* $override is set to true to avoid conflicts with the core endpoint.
102	* Do not sync to WordPress core.
103	*/
104	true
105	);
106
107	// Lists/updates a single global style variation based on the given id.
108	register_rest_route(
109	$this->namespace,
110	'/' . $this->rest_base . '/(?P<id>[\/\w-]+)',
111	array(
112	array(
113	'methods' => WP_REST_Server::READABLE,
114	'callback' => array( $this, 'get_item' ),
115	'permission_callback' => array( $this, 'get_item_permissions_check' ),
116	'args' => array(
117	'id' => array(
118	'description' => __( 'The id of a template', 'gutenberg' ),
119	'type' => 'string',
120	'sanitize_callback' => array( $this, '_sanitize_global_styles_callback' ),
121	),
122	),
123	),
124	array(
125	'methods' => WP_REST_Server::EDITABLE,
126	'callback' => array( $this, 'update_item' ),
127	'permission_callback' => array( $this, 'update_item_permissions_check' ),
128	'args' => $this->get_endpoint_args_for_item_schema( WP_REST_Server::EDITABLE ),
129	),
130	'schema' => array( $this, 'get_public_item_schema' ),
131	'allow_batch' => $this->allow_batch,
132	),
133	/*
134	* $override is set to true to avoid conflicts with the core endpoint.
135	* Do not sync to WordPress core.
136	*/
137	true
138	);
139	}
140
141	/**
142	* Sanitize the global styles ID or stylesheet to decode endpoint.
143	* For example, `wp/v2/global-styles/twentytwentytwo%200.4.0`
144	* would be decoded to `twentytwentytwo 0.4.0`.
145	*
146	* @since 5.9.0
147	*
148	* @param string $id_or_stylesheet Global styles ID or stylesheet.
149	* @return string Sanitized global styles ID or stylesheet.
150	*/
151	public function _sanitize_global_styles_callback( $id_or_stylesheet ) {
152	return urldecode( $id_or_stylesheet );
153	}
154
155	/**
156	* Get the post, if the ID is valid.
157	*
158	* @since 5.9.0
159	*
160	* @param int $id Supplied ID.
161	* @return WP_Post\|WP_Error Post object if ID is valid, WP_Error otherwise.
162	*/
163	protected function get_post( $id ) {
164	$error = new WP_Error(
165	'rest_global_styles_not_found',
166	__( 'No global styles config exist with that id.', 'gutenberg' ),
167	array( 'status' => 404 )
168	);
169
170	$id = (int) $id;
171	if ( $id <= 0 ) {
172	return $error;
173	}
174
175	$post = get_post( $id );
176	if ( empty( $post ) \|\| empty( $post->ID ) \|\| $this->post_type !== $post->post_type ) {
177	return $error;
178	}
179
180	return $post;
181	}
182
183	/**
184	* Checks if a given request has access to read a single global style.
185	*
186	* @since 5.9.0
187	*
188	* @param WP_REST_Request $request Full details about the request.
189	* @return true\|WP_Error True if the request has read access, WP_Error object otherwise.
190	*/
191	public function get_item_permissions_check( $request ) {
192	$post = $this->get_post( $request['id'] );
193	if ( is_wp_error( $post ) ) {
194	return $post;
195	}
196
197	if ( 'edit' === $request['context'] && $post && ! $this->check_update_permission( $post ) ) {
198	return new WP_Error(
199	'rest_forbidden_context',
200	__( 'Sorry, you are not allowed to edit this global style.', 'gutenberg' ),
201	array( 'status' => rest_authorization_required_code() )
202	);
203	}
204
205	if ( ! $this->check_read_permission( $post ) ) {
206	return new WP_Error(
207	'rest_cannot_view',
208	__( 'Sorry, you are not allowed to view this global style.', 'gutenberg' ),
209	array( 'status' => rest_authorization_required_code() )
210	);
211	}
212
213	return true;
214	}
215
216	/**
217	* Checks if a global style can be read.
218	*
219	* @since 5.9.0
220	*
221	* @param WP_Post $post Post object.
222	* @return bool Whether the post can be read.
223	*/
224	public function check_read_permission( $post ) {
225	return current_user_can( 'read_post', $post->ID );
226	}
227
228	/**
229	* Checks if a given request has access to write a single global styles config.
230	*
231	* @since 5.9.0
232	*
233	* @param WP_REST_Request $request Full details about the request.
234	* @return true\|WP_Error True if the request has write access for the item, WP_Error object otherwise.
235	*/
236	public function update_item_permissions_check( $request ) {
237	$post = $this->get_post( $request['id'] );
238	if ( is_wp_error( $post ) ) {
239	return $post;
240	}
241
242	if ( $post && ! $this->check_update_permission( $post ) ) {
243	return new WP_Error(
244	'rest_cannot_edit',
245	__( 'Sorry, you are not allowed to edit this global style.', 'gutenberg' ),
246	array( 'status' => rest_authorization_required_code() )
247	);
248	}
249
250	return true;
251	}
252
253	/**
254	* Prepares a single global styles config for update.
255	*
256	* @since 5.9.0
257	* @since 6.2.0 Added validation of styles.css property.
258	* @since 6.6.0 Added registration of block style variations from theme.json sources (theme.json, user theme.json, partials).
259	*
260	* @param WP_REST_Request $request Request object.
261	* @return stdClass\|WP_Error Prepared item on success. WP_Error on when the custom CSS is not valid.
262	*/
263	protected function prepare_item_for_database( $request ) {
264	$changes = new stdClass();
265	$changes->ID = $request['id'];
266
267	$post = get_post( $request['id'] );
268	$existing_config = array();
269	if ( $post ) {
270	$existing_config = json_decode( $post->post_content, true );
271	$json_decoding_error = json_last_error();
272	if ( JSON_ERROR_NONE !== $json_decoding_error \|\| ! isset( $existing_config['isGlobalStylesUserThemeJSON'] ) \|\|
273	! $existing_config['isGlobalStylesUserThemeJSON'] ) {
274	$existing_config = array();
275	}
276	}
277
278	if ( isset( $request['styles'] ) \|\| isset( $request['settings'] ) ) {
279	$config = array();
280	if ( isset( $request['styles'] ) ) {
281	if ( isset( $request['styles']['css'] ) ) {
282	$css_validation_result = $this->validate_custom_css( $request['styles']['css'] );
283	if ( is_wp_error( $css_validation_result ) ) {
284	return $css_validation_result;
285	}
286	}
287	$config['styles'] = $request['styles'];
288	} elseif ( isset( $existing_config['styles'] ) ) {
289	$config['styles'] = $existing_config['styles'];
290	}
291
292	// Register theme-defined variations e.g. from block style variation partials under `/styles`.
293	$variations = WP_Theme_JSON_Resolver_Gutenberg::get_style_variations( 'block' );
294	gutenberg_register_block_style_variations_from_theme_json_partials( $variations );
295
296	if ( isset( $request['settings'] ) ) {
297	$config['settings'] = $request['settings'];
298	} elseif ( isset( $existing_config['settings'] ) ) {
299	$config['settings'] = $existing_config['settings'];
300	}
301	$config['isGlobalStylesUserThemeJSON'] = true;
302	$config['version'] = WP_Theme_JSON_Gutenberg::LATEST_SCHEMA;
303	/**
304	* JSON encode the data stored in post content.
305	* Escape characters that are likely to be mangled by HTML filters: "<>&".
306	*
307	* This data is later re-encoded by {@see gutenberg_filter_global_styles_post()}.
308	* The escaping is also applied here as a precaution.
309	*/
310	$changes->post_content = wp_json_encode( $config, JSON_UNESCAPED_SLASHES \| JSON_HEX_TAG \| JSON_HEX_AMP );
311	}
312
313	// Post title.
314	if ( isset( $request['title'] ) ) {
315	if ( is_string( $request['title'] ) ) {
316	$changes->post_title = $request['title'];
317	} elseif ( ! empty( $request['title']['raw'] ) ) {
318	$changes->post_title = $request['title']['raw'];
319	}
320	}
321
322	return $changes;
323	}
324
325	/**
326	* Prepare a global styles config output for response.
327	*
328	* @since 5.9.0
329	* @since 6.2.0 Handling of style.css was added to WP_Theme_JSON.
330	* @since 6.6.0 Added custom relative theme file URIs to `_links`.
331	*
332	* @param WP_Post $post Global Styles post object.
333	* @param WP_REST_Request $request Request object.
334	* @return WP_REST_Response Response object.
335	*/
336	public function prepare_item_for_response( $post, $request ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
337	$raw_config = json_decode( $post->post_content, true );
338	$is_global_styles_user_theme_json = isset( $raw_config['isGlobalStylesUserThemeJSON'] ) && true === $raw_config['isGlobalStylesUserThemeJSON'];
339	$config = array();
340	$theme_json = null;
341	if ( $is_global_styles_user_theme_json ) {
342	$theme_json = new WP_Theme_JSON_Gutenberg( $raw_config, 'custom' );
343	$config = $theme_json->get_raw_data();
344	}
345
346	// Base fields for every post.
347	$data = array();
348	$fields = $this->get_fields_for_response( $request );
349
350	if ( rest_is_field_included( 'id', $fields ) ) {
351	$data['id'] = $post->ID;
352	}
353
354	if ( rest_is_field_included( 'title', $fields ) ) {
355	$data['title'] = array();
356	}
357	if ( rest_is_field_included( 'title.raw', $fields ) ) {
358	$data['title']['raw'] = $post->post_title;
359	}
360	if ( rest_is_field_included( 'title.rendered', $fields ) ) {
361	add_filter( 'protected_title_format', array( $this, 'protected_title_format' ) );
362	add_filter( 'private_title_format', array( $this, 'protected_title_format' ) );
363
364	$data['title']['rendered'] = get_the_title( $post->ID );
365
366	remove_filter( 'protected_title_format', array( $this, 'protected_title_format' ) );
367	remove_filter( 'private_title_format', array( $this, 'protected_title_format' ) );
368	}
369
370	if ( rest_is_field_included( 'settings', $fields ) ) {
371	$data['settings'] = ! empty( $config['settings'] ) && $is_global_styles_user_theme_json ? $config['settings'] : new stdClass();
372	}
373
374	if ( rest_is_field_included( 'styles', $fields ) ) {
375	$data['styles'] = ! empty( $config['styles'] ) && $is_global_styles_user_theme_json ? $config['styles'] : new stdClass();
376	}
377
378	$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
379	$data = $this->add_additional_fields_to_object( $data, $request );
380	$data = $this->filter_response_by_context( $data, $context );
381
382	// Wrap the data in a response object.
383	$response = rest_ensure_response( $data );
384
385	if ( rest_is_field_included( '_links', $fields ) \|\| rest_is_field_included( '_embedded', $fields ) ) {
386	$links = $this->prepare_links( $post->ID );
387	// Only return resolved URIs for get requests to user theme JSON.
388	if ( $theme_json ) {
389	$resolved_theme_uris = WP_Theme_JSON_Resolver_Gutenberg::get_resolved_theme_uris( $theme_json );
390	if ( ! empty( $resolved_theme_uris ) ) {
391	$links['https://api.w.org/theme-file'] = $resolved_theme_uris;
392	}
393	}
394	$response->add_links( $links );
395	if ( ! empty( $links['self']['href'] ) ) {
396	$actions = $this->get_available_actions( $post, $request );
397	$self = $links['self']['href'];
398	foreach ( $actions as $rel ) {
399	$response->add_link( $rel, $self );
400	}
401	}
402	}
403
404	return $response;
405	}
406
407	/**
408	* Prepares links for the request.
409	*
410	* @since 5.9.0
411	* @since 6.3.0 Adds revisions count and rest URL href to version-history.
412	*
413	* @param integer $id ID.
414	* @return array Links for the given post.
415	*/
416	protected function prepare_links( $id ) {
417	$base = sprintf( '%s/%s', $this->namespace, $this->rest_base );
418
419	$links = array(
420	'self' => array(
421	'href' => rest_url( trailingslashit( $base ) . $id ),
422	),
423	'about' => array(
424	'href' => rest_url( 'wp/v2/types/' . $this->post_type ),
425	),
426	);
427
428	if ( post_type_supports( $this->post_type, 'revisions' ) ) {
429	$revisions = wp_get_latest_revision_id_and_total_count( $id );
430	$revisions_count = ! is_wp_error( $revisions ) ? $revisions['count'] : 0;
431	$revisions_base = sprintf( '/%s/%d/revisions', $base, $id );
432	$links['version-history'] = array(
433	'href' => rest_url( $revisions_base ),
434	'count' => $revisions_count,
435	);
436	}
437
438	return $links;
439	}
440
441	/**
442	* Get the link relations available for the post and current user.
443	*
444	* @since 5.9.0
445	* @since 6.2.0 Added 'edit-css' action.
446	* @since 6.6.0 Added $post and $request parameters.
447	*
448	* @param WP_Post $post Post object.
449	* @param WP_REST_Request $request Request object.
450	* @return array List of link relations.
451	*/
452	protected function get_available_actions( $post, $request ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
453	$rels = array();
454
455	$post_type = get_post_type_object( $post->post_type );
456	if ( current_user_can( $post_type->cap->publish_posts ) ) {
457	$rels[] = 'https://api.w.org/action-publish';
458	}
459
460	if ( current_user_can( 'edit_css' ) ) {
461	$rels[] = 'https://api.w.org/action-edit-css';
462	}
463
464	return $rels;
465	}
466
467	/**
468	* Retrieves the query params for the global styles collection.
469	*
470	* @since 5.9.0
471	*
472	* @return array Collection parameters.
473	*/
474	public function get_collection_params() {
475	return array();
476	}
477
478	/**
479	* Retrieves the global styles type' schema, conforming to JSON Schema.
480	*
481	* @since 5.9.0
482	*
483	* @return array Item schema data.
484	*/
485	public function get_item_schema() {
486	if ( $this->schema ) {
487	return $this->add_additional_fields_schema( $this->schema );
488	}
489
490	$schema = array(
491	'$schema' => 'http://json-schema.org/draft-04/schema#',
492	'title' => $this->post_type,
493	'type' => 'object',
494	'properties' => array(
495	'id' => array(
496	'description' => __( 'ID of global styles config.', 'gutenberg' ),
497	'type' => 'string',
498	'context' => array( 'embed', 'view', 'edit' ),
499	'readonly' => true,
500	),
501	'styles' => array(
502	'description' => __( 'Global styles.', 'gutenberg' ),
503	'type' => array( 'object' ),
504	'context' => array( 'view', 'edit' ),
505	),
506	'settings' => array(
507	'description' => __( 'Global settings.', 'gutenberg' ),
508	'type' => array( 'object' ),
509	'context' => array( 'view', 'edit' ),
510	),
511	'title' => array(
512	'description' => __( 'Title of the global styles variation.', 'gutenberg' ),
513	'type' => array( 'object', 'string' ),
514	'default' => '',
515	'context' => array( 'embed', 'view', 'edit' ),
516	'properties' => array(
517	'raw' => array(
518	'description' => __( 'Title for the global styles variation, as it exists in the database.', 'gutenberg' ),
519	'type' => 'string',
520	'context' => array( 'view', 'edit', 'embed' ),
521	),
522	'rendered' => array(
523	'description' => __( 'HTML title for the post, transformed for display.', 'gutenberg' ),
524	'type' => 'string',
525	'context' => array( 'view', 'edit', 'embed' ),
526	'readonly' => true,
527	),
528	),
529	),
530	),
531	);
532
533	$this->schema = $schema;
534
535	return $this->add_additional_fields_schema( $this->schema );
536	}
537
538	/**
539	* Checks if a given request has access to read a single theme global styles config.
540	*
541	* @since 5.9.0
542	* @since 6.7.0 Allow users with edit post capabilities to view theme global styles.
543	*
544	* @param WP_REST_Request $request Full details about the request.
545	* @return true\|WP_Error True if the request has read access for the item, WP_Error object otherwise.
546	*/
547	public function get_theme_item_permissions_check( $request ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
548	/*
549	* Verify if the current user has edit_posts capability.
550	*/
551	if ( current_user_can( 'edit_posts' ) ) {
552	return true;
553	}
554
555	foreach ( get_post_types( array( 'show_in_rest' => true ), 'objects' ) as $post_type ) {
556	if ( current_user_can( $post_type->cap->edit_posts ) ) {
557	return true;
558	}
559	}
560
561	/*
562	* Verify if the current user has edit_theme_options capability.
563	*/
564	if ( current_user_can( 'edit_theme_options' ) ) {
565	return true;
566	}
567
568	return new WP_Error(
569	'rest_cannot_read_global_styles',
570	__( 'Sorry, you are not allowed to access the global styles on this site.', 'gutenberg' ),
571	array(
572	'status' => rest_authorization_required_code(),
573	)
574	);
575	}
576
577	/**
578	* Returns the given theme global styles config.
579	*
580	* @since 5.9.0
581	*
582	* @param WP_REST_Request $request The request instance.
583	* @return WP_REST_Response\|WP_Error
584	*/
585	public function get_theme_item( $request ) {
586	if ( get_stylesheet() !== $request['stylesheet'] ) {
587	// This endpoint only supports the active theme for now.
588	return new WP_Error(
589	'rest_theme_not_found',
590	__( 'Theme not found.', 'gutenberg' ),
591	array( 'status' => 404 )
592	);
593	}
594
595	$theme = WP_Theme_JSON_Resolver_Gutenberg::get_merged_data( 'theme' );
596	$fields = $this->get_fields_for_response( $request );
597	$data = array();
598
599	if ( rest_is_field_included( 'settings', $fields ) ) {
600	$data['settings'] = $theme->get_settings();
601	}
602
603	if ( rest_is_field_included( 'styles', $fields ) ) {
604	$raw_data = $theme->get_raw_data();
605	$data['styles'] = $raw_data['styles'] ?? array();
606	}
607
608	$context = ! empty( $request['context'] ) ? $request['context'] : 'view';
609	$data = $this->add_additional_fields_to_object( $data, $request );
610	$data = $this->filter_response_by_context( $data, $context );
611	$response = rest_ensure_response( $data );
612
613	if ( rest_is_field_included( '_links', $fields ) \|\| rest_is_field_included( '_embedded', $fields ) ) {
614	$links = array(
615	'self' => array(
616	'href' => rest_url( sprintf( '%s/%s/themes/%s', $this->namespace, $this->rest_base, $request['stylesheet'] ) ),
617	),
618	);
619	$resolved_theme_uris = WP_Theme_JSON_Resolver_Gutenberg::get_resolved_theme_uris( $theme );
620	if ( ! empty( $resolved_theme_uris ) ) {
621	$links['https://api.w.org/theme-file'] = $resolved_theme_uris;
622	}
623
624	$response->add_links( $links );
625	}
626
627	return $response;
628	}
629
630	/**
631	* Checks if a given request has access to read a single theme global styles config.
632	*
633	* @since 6.0.0
634	*
635	* @param WP_REST_Request $request Full details about the request.
636	* @return true\|WP_Error True if the request has read access for the item, WP_Error object otherwise.
637	*/
638	public function get_theme_items_permissions_check( $request ) {
639	return $this->get_theme_item_permissions_check( $request );
640	}
641
642	/**
643	* Returns the given theme global styles variations.
644	*
645	* @since 6.0.0
646	* @since 6.2.0 Returns parent theme variations, if they exist.
647	* @since 6.4.0 Removed unnecessary local variable.
648	* @since 6.6.0 Added custom relative theme file URIs to `_links` for each item.
649	*
650	* @param WP_REST_Request $request The request instance.
651	*
652	* @return WP_REST_Response\|WP_Error
653	*/
654	public function get_theme_items( $request ) {
655	if ( get_stylesheet() !== $request['stylesheet'] ) {
656	// This endpoint only supports the active theme for now.
657	return new WP_Error(
658	'rest_theme_not_found',
659	__( 'Theme not found.', 'gutenberg' ),
660	array( 'status' => 404 )
661	);
662	}
663
664	$response = array();
665
666	// Register theme-defined variations e.g. from block style variation partials under `/styles`.
667	$partials = WP_Theme_JSON_Resolver_Gutenberg::get_style_variations( 'block' );
668	gutenberg_register_block_style_variations_from_theme_json_partials( $partials );
669
670	$variations = WP_Theme_JSON_Resolver_Gutenberg::get_style_variations();
671
672	// Add resolved theme asset links.
673	foreach ( $variations as $variation ) {
674	$variation_theme_json = new WP_Theme_JSON_Gutenberg( $variation );
675	$resolved_theme_uris = WP_Theme_JSON_Resolver_Gutenberg::get_resolved_theme_uris( $variation_theme_json );
676	$data = rest_ensure_response( $variation );
677	if ( ! empty( $resolved_theme_uris ) ) {
678	$data->add_links(
679	array(
680	'https://api.w.org/theme-file' => $resolved_theme_uris,
681	)
682	);
683	}
684	$response[] = $this->prepare_response_for_collection( $data );
685	}
686
687	return rest_ensure_response( $response );
688	}
689
690	/**
691	* Validate style.css as valid CSS.
692	*
693	* Currently just checks that CSS will not break an HTML STYLE tag.
694	*
695	* @since 6.2.0
696	* @since 6.4.0 Changed method visibility to protected.
697	* @since 7.0.0 Only restricts contents which risk prematurely closing the STYLE element,
698	* either through a STYLE end tag or a prefix of one which might become a
699	* full end tag when combined with the contents of other styles.
700	*
701	* @param string $css CSS to validate.
702	* @return true\|WP_Error True if the input was validated, otherwise WP_Error.
703	*/
704	protected function validate_custom_css( $css ) {
705	$length = strlen( $css );
706	for (
707	$at = strcspn( $css, '<' );
708	$at < $length;
709	$at += strcspn( $css, '<', ++$at )
710	) {
711	$remaining_strlen = $length - $at;
712	/**
713	* Custom CSS text is expected to render inside an HTML STYLE element.
714	* A STYLE closing tag must not appear within the CSS text because it
715	* would close the element prematurely.
716	*
717	* The text must also not end with a partial closing tag (e.g., `<`,
718	* `</`, … `</style`) because subsequent styles which are concatenated
719	* could complete it, forming a valid `</style>` tag.
720	*
721	* Example:
722	*
723	* $style_a = 'p { font-weight: bold; </sty';
724	* $style_b = 'le> gotcha!';
725	* $combined = "{$style_a}{$style_b}";
726	*
727	* $style_a = 'p { font-weight: bold; </style';
728	* $style_b = 'p > b { color: red; }';
729	* $combined = "{$style_a}\n{$style_b}";
730	*
731	* Note how in the second example, both of the style contents are benign
732	* when analyzed on their own. The first style was likely the result of
733	* improper truncation, while the second is perfectly sound. It was only
734	* through concatenation that these two scripts combined to form content
735	* that would have broken out of the containing STYLE element, thus
736	* corrupting the page and potentially introducing security issues.
737	*
738	* @link https://html.spec.whatwg.org/multipage/parsing.html#rawtext-end-tag-name-state
739	*/
740	$possible_style_close_tag = 0 === substr_compare(
741	$css,
742	'</style',
743	$at,
744	min( 7, $remaining_strlen ),
745	true
746	);
747	if ( $possible_style_close_tag ) {
748	if ( $remaining_strlen < 8 ) {
749	return new WP_Error(
750	'rest_custom_css_illegal_markup',
751	sprintf(
752	/* translators: %s is the CSS that was provided. */
753	__( 'The CSS must not end in "%s".', 'gutenberg' ),
754	esc_html( substr( $css, $at ) )
755	),
756	array( 'status' => 400 )
757	);
758	}
759
760	if ( 1 === strspn( $css, " \t\f\r\n/>", $at + 7, 1 ) ) {
761	return new WP_Error(
762	'rest_custom_css_illegal_markup',
763	sprintf(
764	/* translators: %s is the CSS that was provided. */
765	__( 'The CSS must not contain "%s".', 'gutenberg' ),
766	esc_html( substr( $css, $at, 8 ) )
767	),
768	array( 'status' => 400 )
769	);
770	}
771	}
772	}
773
774	return true;
775	}
776	}
777