Prevent blank page caused by invalid graphql_general_settings in public/User.php

[bicodrex]

Today, after installing the WPGraphQL plugin on my WordPress server running ReactPress v3.4.0, I noticed that pages using ReactPress were rendering blank. Checking the PHP error log, I found the following stack trace:

Stack trace:
#0 /var/www/html/wp-content/plugins/reactpress/public/User.php(91): ReactPress\User\User->repr_load_react_app()
#1 /var/www/html/wp-includes/class-wp-hook.php(324): ReactPress\User\User->enqueue_scripts('')
#2 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)
#3 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#4 /var/www/html/wp-includes/script-loader.php(2299): do_action('wp_enqueue_scri...')
#5 /var/www/html/wp-includes/class-wp-hook.php(324): wp_enqueue_scripts('')
#6 /var/www/html/wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)
#7 /var/www/html/wp-includes/plugin.php(517): WP_Hook->do_action(Array)
#8 /var/www/html/wp-includes/general-template.php(3192): do_action('wp_head')
#9 /var/www/html/wp-includes/template-canvas.php(17): wp_head()
#10 /var/www/html/wp-includes/template-loader.php(106): include('/var/www/html/w...')
#11 /var/www/html/wp-blog-header.php(19): require_once('/var/www/html/w...')
#12 /var/www/html/index.php(17): require('/var/www/html/w...')
#13 {main}
  thrown in /var/www/html/wp-content/plugins/reactpress/public/User.php on line 223

Oddly enough, the crash occurred even after disabling and uninstalling WPGraphQL.

Why this crashes

After some debugging, I discovered the following behavior of get_option('graphql_general_settings'):

• If WPGraphQL has never been installed, because the option does not exist yet, it returns the default passed to get_option(). In this case ['graphql_endpoint' => 'graphql'] is used, so the code works as expected.
• It returns an empty string ('') if WPGraphQL has been installed but its settings page has never been saved. In this case, WordPress does not use the default value. As a result, the code tries to access ['graphql_endpoint'] on a string, which causes a fatal error: Uncaught TypeError: Cannot access offset of type string on string
• It returns a valid array only after the user saves the plugin's settings via the admin interface. This array looks like:

array (
  'graphql_endpoint' => 'graphql',
  'restrict_endpoint_to_logged_in_users' => 'off',
  'batch_queries_enabled' => 'on',
  'batch_limit' => '10',
  'query_depth_enabled' => 'off',
  'query_depth_max' => 10,
  'query_analyzer_enabled' => 'off',
  'graphiql_enabled' => 'on',
  'show_graphiql_link_in_admin_bar' => 'on',
  'delete_data_on_deactivate' => 'on',
  'debug_mode_enabled' => 'off',
  'tracing_enabled' => 'off',
  'tracing_user_role' => 'administrator',
  'query_logs_enabled' => 'off',
  'query_log_user_role' => 'administrator',
  'public_introspection_enabled' => 'off',
)

The fix

The proposed solution adds a safety check to ensure the option value is an array before accessing ['graphql_endpoint']. If it's not, the fallback value 'graphql' is used.
This prevents the crash when the option is missing or improperly initialized and ensures a more robust and fault-tolerant behavior.