Preload REST API responses for plugins on Connectors screen and add support for preloading non-OK responses

src/wp-admin/options-connectors.php

@@ -32,6 +32,45 @@
 // Set parent file for menu highlighting.
 $parent_file = 'options-general.php';
 
+/**
+ * Preloads the REST API responses the Connectors UI fetches on mount.
+ *
+ * Without this, the page does a network round-trip for site settings,
+ * plugin capability discovery, and each connector's plugin record after
+ * the JS hydrates, which noticeably delays first paint.
+ *
+ * @since 7.0.0
+ * @access private
+ *
+ * @param array<string|array{ 0: string, 1?: 'GET'|'OPTIONS', 2?: int<100, 599>|int<100, 599>[] }> $preload_paths Paths already queued for preloading.
+ * @return array<string|array{ 0: string, 1?: 'GET'|'OPTIONS', 2?: int<100, 599>|int<100, 599>[] }> Paths with the Connectors-specific requests appended.
+ */
+function _wp_connectors_preload_paths( array $preload_paths ): array {
+	// getEntityRecord( 'root', 'site' ) in stage.tsx / use-connector-plugin.ts.
+	$preload_paths[] = '/wp/v2/settings';
+
+	// canUser( 'create', { kind: 'root', name: 'plugin' } ) in stage.tsx.
+	$preload_paths[] = array( '/wp/v2/plugins', 'OPTIONS' );
+
+	// AiPluginCallout in routes/connectors-home/ai-plugin-callout.tsx queries this
+	// hardcoded ID to check whether the WP AI plugin is installed/active.
+	$preload_paths[] = array( '/wp/v2/plugins/ai/ai?context=edit', 'GET', array( 200, 404 ) );
+
+	// getEntityRecord( 'root', 'plugin', <basename> ) per connector in use-connector-plugin.ts.
+	foreach ( wp_get_connectors() as $connector_data ) {
+		if ( empty( $connector_data['plugin']['file'] ) ) {
+			continue;
+		}
+		// core-data's plugin entity uses the basename with `.php` stripped
+		// as the record key (see routes/connectors-home/use-connector-plugin.ts).
+		$basename        = preg_replace( '/\.php$/', '', plugin_basename( $connector_data['plugin']['file'] ) );
+		$preload_paths[] = array( '/wp/v2/plugins/' . $basename . '?context=edit', 'GET', array( 200, 404 ) );
+	}
+
+	return $preload_paths;
+}
+add_filter( 'options-connectors-wp-admin_preload_paths', '_wp_connectors_preload_paths' );
+
 require_once ABSPATH . 'wp-admin/admin-header.php';
 
 // Render the Connectors page.

src/wp-includes/class-wp-http-response.php

@@ -27,7 +27,7 @@ class WP_HTTP_Response {
 	 * Response headers.
 	 *
 	 * @since 4.4.0
-	 * @var array
+	 * @var array<string, string>
 	 */
 	public $headers;
 

src/wp-includes/rest-api.php

@@ -2930,9 +2930,13 @@ function rest_sanitize_value_from_schema( $value, $args, $param = '' ) {
  *
  * @since 5.0.0
  *
- * @param array  $memo Reduce accumulator.
- * @param string $path REST API path to preload.
+ * @param array        $memo Reduce accumulator.
+ * @param string|array $path REST API path to preload.
  * @return array Modified reduce accumulator.
+ *
+ * @phpstan-param array<string, array{ body: array<mixed>, headers: array<string, string> } | array<string, array{ body: array<mixed>, headers: array<string, string> }> > $memo
+ * @phpstan-param string|array{ 0: string, 1?: 'GET'|'OPTIONS', 2?: int<100, 599>|int<100, 599>[] } $path
+ * @phpstan-return array<string, array{ body: array<mixed>, headers: array<string, string> } | array<string, array{ body: array<mixed>, headers: array<string, string> }> >
  */
 function rest_preload_api_request( $memo, $path ) {
 	/*
@@ -2947,14 +2951,25 @@ function rest_preload_api_request( $memo, $path ) {
 		return $memo;
 	}
 
-	$method = 'GET';
-	if ( is_array( $path ) && 2 === count( $path ) ) {
-		$method = end( $path );
-		$path   = reset( $path );
-
+	$method           = 'GET';
+	$allowed_statuses = array( 200 );
+	if ( is_array( $path ) ) {
+		$path_array = $path;
+		$path       = array_shift( $path_array );
+		if ( ! is_string( $path ) ) {
+			return $memo;
+		}
+		$method = array_shift( $path_array );
 		if ( ! in_array( $method, array( 'GET', 'OPTIONS' ), true ) ) {
 			$method = 'GET';
 		}
+		$statuses = array_shift( $path_array );
+		if ( $statuses ) {
+			$statuses = array_filter( (array) $statuses, 'is_int' );
+			if ( count( $statuses ) > 0 ) {
+				$allowed_statuses = $statuses;
+			}
+		}
 	}
 
 	// Remove trailing slashes at the end of the REST API path (query part).
@@ -2964,11 +2979,11 @@ function rest_preload_api_request( $memo, $path ) {
 	}
 
 	$path_parts = parse_url( $path );
-	if ( false === $path_parts ) {
+	if ( false === $path_parts || ! isset( $path_parts['path'] ) ) {
 		return $memo;
 	}
 
-	if ( isset( $path_parts['path'] ) && '/' !== $path_parts['path'] ) {
+	if ( '/' !== $path_parts['path'] ) {
 		// Remove trailing slashes from the "path" part of the REST API path.
 		$path_parts['path'] = untrailingslashit( $path_parts['path'] );
 		$path               = str_contains( $path, '?' ) ?
@@ -2983,12 +2998,20 @@ function rest_preload_api_request( $memo, $path ) {
 	}
 
 	$response = rest_do_request( $request );
-	if ( 200 === $response->status ) {
+	if ( in_array( $response->status, $allowed_statuses, true ) ) {
 		$server = rest_get_server();
 		/** This filter is documented in wp-includes/rest-api/class-wp-rest-server.php */
 		$response = apply_filters( 'rest_post_dispatch', rest_ensure_response( $response ), $server, $request );
-		$embed    = $request->has_param( '_embed' ) ? rest_parse_embed_param( $request['_embed'] ) : false;
-		$data     = (array) $server->response_to_data( $response, $embed );
+		if ( ! $response instanceof WP_REST_Response ) {
+			return $memo;
+		}
+
+		if ( $request->has_param( '_embed' ) && ( is_array( $request['_embed'] ) || is_string( $request['_embed'] ) ) ) {
+			$embed = rest_parse_embed_param( $request['_embed'] );
+		} else {
+			$embed = false;
+		}
+		$data = (array) $server->response_to_data( $response, $embed );
 
 		if ( 'OPTIONS' === $method ) {
 			$memo[ $method ][ $path ] = array(

tests/phpunit/tests/rest-api.php

@@ -938,12 +938,24 @@ public function test_register_rest_route_without_server() {
 		$this->assertSame( $routes['/test-ns/test'][0]['methods'], array( 'GET' => true ) );
 	}
 
-	public function test_rest_preload_api_request_with_method() {
+	/**
+	 * @ticket 65215
+	 */
+	public function test_rest_preload_api_request_with_method_and_allowed_statuses() {
 		$rest_server               = $GLOBALS['wp_rest_server'];
 		$GLOBALS['wp_rest_server'] = null;
 
+		$exiting_post_id  = self::factory()->post->create();
+		$missing_post1_id = 10001;
+		$missing_post2_id = 10002;
+		$this->assertNull( get_post( $missing_post1_id ), "Expected post with ID $missing_post1_id to not exist." );
+		$this->assertNull( get_post( $missing_post2_id ), "Expected post with ID $missing_post2_id to not exist." );
+
 		$preload_paths = array(
 			'/wp/v2/types',
+			array( "/wp/v2/posts/$exiting_post_id", 'GET', array( 200 ) ),
+			array( "/wp/v2/posts/$missing_post1_id", 'GET', array( 200, 404 ) ),
+			array( "/wp/v2/posts/$missing_post2_id", 'GET' ),
 			array( '/wp/v2/media', 'OPTIONS' ),
 		);
 
@@ -953,9 +965,18 @@ public function test_rest_preload_api_request_with_method() {
 			array()
 		);
 
-		$this->assertSame( array_keys( $preload_data ), array( '/wp/v2/types', 'OPTIONS' ) );
+		$this->assertSame( array_keys( $preload_data ), array( '/wp/v2/types', "/wp/v2/posts/$exiting_post_id", "/wp/v2/posts/$missing_post1_id", 'OPTIONS' ) );
 		$this->assertArrayHasKey( '/wp/v2/media', $preload_data['OPTIONS'] );
 
+		$existing_post_response_data = $preload_data[ "/wp/v2/posts/$exiting_post_id" ];
+		$this->assertTrue( isset( $existing_post_response_data['body']['id'] ), 'Expected body.id to be exist.' );
+		$this->assertSame( $exiting_post_id, $existing_post_response_data['body']['id'] );
+
+		$missing_post_response_data = $preload_data[ "/wp/v2/posts/$missing_post1_id" ];
+		$this->assertTrue( isset( $missing_post_response_data['body']['code'], $missing_post_response_data['body']['data']['status'] ), 'Expected body.code and body.data.status to exist.' );
+		$this->assertSame( 'rest_post_invalid_id', $missing_post_response_data['body']['code'] );
+		$this->assertSame( 404, $missing_post_response_data['body']['data']['status'] );
+
 		$GLOBALS['wp_rest_server'] = $rest_server;
 	}