Move handling of backup post to be implicit so that api requests can …

…be more safely used at call site

lib/client-assets.php

@@ -910,7 +910,19 @@ function gutenberg_api_request( $path ) {
 		$request->set_query_params( $query_params );
 	}
 
+
+	// Ensure the global $post remains the same after the API request is made.
+	// Because API requests can call the_content and other filters, callbacks
+	// can unexpectedly modify $post resulting in issues
+	// like https://github.com/WordPress/gutenberg/issues/7468.
+	global $post;
+	$backup_global_post = $post;
+
 	$response = rest_do_request( $request );
+
+	// restore the global post
+	$post = $backup_global_post;
+
 	if ( 200 === $response->status ) {
 		$server = rest_get_server();
 		$data   = (array) $response->get_data();
@@ -1462,22 +1474,12 @@ function gutenberg_editor_scripts_and_styles( $hook ) {
 	 */
 	$preload_paths = apply_filters( 'block_editor_preload_paths', $preload_paths, $post );
 
-	// Ensure the global $post remains the same after
-	// API data is preloaded. Because API preloading
-	// can call the_content and other filters, callbacks
-	// can unexpectedly modify $post resulting in issues
-	// like https://github.com/WordPress/gutenberg/issues/7468.
-	$backup_global_post = $post;
-
 	$preload_data = array_reduce(
 		$preload_paths,
 		'gutenberg_preload_api_request',
 		array()
 	);
 
-	// Restore the global $post as it was before API preloading.
-	$post = $backup_global_post;
-
 	wp_add_inline_script(
 		'wp-api-fetch',
 		sprintf( 'wp.apiFetch.use( wp.apiFetch.createPreloadingMiddleware( %s ) );', wp_json_encode( $preload_data ) ),