Bootstrap/Load: Introduce fatal error handler.

This changeset introduces a `WP_Fatal_Error_Handler` class that detects fatal errors and displays a more user-friendly message about the site experiencing technical difficulties.

Websites that have custom requirements in that regard can implement their own fatal error handler by adding a `fatal-error-handler.php` drop-in that returns the handler instance to use, which must be based on a class that inherits `WP_Fatal_Error_Handler`. That handler will then be used in place of the default one. Alternatively, the fatal error handler feature can be completely disable through a constant `WP_DISABLE_FATAL_ERROR_HANDLER`.

Websites that would like to modify specifically the error template displayed in the frontend can add a `php-error.php` drop-in that works similarly to the existing `db-error.php` drop-in. For more granular customization, the fatal error handler also includes new filters `wp_should_handle_php_error`, `wp_php_error_message` and `wp_php_error_args`.

Props afragen, bradleyt, flixos90, ocean90, schlessera, SergeyBiryukov, spacedmonkey, timothyblynjacobs.
See #46130, #44458.


git-svn-id: https://develop.svn.wordpress.org/trunk@44962 602fd350-edb4-49c9-b593-d223f7449a82
This commit is contained in:
Felix Arntz 2019-03-21 16:02:05 +00:00
parent 1d41c6e787
commit b06444e859
3 changed files with 253 additions and 0 deletions

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@ -0,0 +1,185 @@
<?php
/**
* Error Protection API: WP_Fatal_Error_Handler class
*
* @package WordPress
* @since 5.2.0
*/
/**
* Core class used as the default shutdown handler for fatal errors.
*
* A drop-in 'fatal-error-handler.php' can be used to override the instance of this class and use a custom
* implementation for the fatal error handler that WordPress registers. The custom class should extend this class and
* can override its methods individually as necessary. The file must return the instance of the class that should be
* registered.
*
* @since 5.2.0
*/
class WP_Fatal_Error_Handler {
/**
* Runs the shutdown handler.
*
* This method is registered via `register_shutdown_function()`.
*
* @since 5.2.0
*/
public function handle() {
// Bail if WordPress executed successfully.
if ( defined( 'WP_EXECUTION_SUCCEEDED' ) && WP_EXECUTION_SUCCEEDED ) {
return;
}
try {
// Bail if no error found.
$error = $this->detect_error();
if ( ! $error ) {
return;
}
// Display the PHP error template.
$this->display_error_template();
} catch ( Exception $e ) {
// Catch exceptions and remain silent.
}
}
/**
* Detects the error causing the crash if it should be handled.
*
* @since 5.2.0
*
* @return array|null Error that was triggered, or null if no error received or if the error should not be handled.
*/
protected function detect_error() {
$error = error_get_last();
// No error, just skip the error handling code.
if ( null === $error ) {
return null;
}
// Bail if this error should not be handled.
if ( ! $this->should_handle_error( $error ) ) {
return null;
}
return $error;
}
/**
* Determines whether we are dealing with an error that WordPress should handle
* in order to protect the admin backend against WSODs.
*
* @since 5.2.0
*
* @param array $error Error information retrieved from error_get_last().
* @return bool Whether WordPress should handle this error.
*/
protected function should_handle_error( $error ) {
$error_types_to_handle = array(
E_ERROR,
E_PARSE,
E_USER_ERROR,
E_COMPILE_ERROR,
E_RECOVERABLE_ERROR,
);
if ( isset( $error['type'] ) && in_array( $error['type'], $error_types_to_handle, true ) ) {
return true;
}
/**
* Filters whether a given thrown error should be handled by the fatal error handler.
*
* This filter is only fired if the error is not already configured to be handled by WordPress core. As such,
* it exclusively allows adding further rules for which errors should be handled, but not removing existing
* ones.
*
* @since 5.2.0
*
* @param bool $should_handle_error Whether the error should be handled by the fatal error handler.
* @param array $error Error information retrieved from error_get_last().
*/
return (bool) apply_filters( 'wp_should_handle_php_error', false, $error );
}
/**
* Displays the PHP error template and sends the HTTP status code, typically 500.
*
* A drop-in 'php-error.php' can be used as a custom template. This drop-in should control the HTTP status code and
* print the HTML markup indicating that a PHP error occurred. Note that this drop-in may potentially be executed
* very early in the WordPress bootstrap process, so any core functions used that are not part of
* `wp-includes/load.php` should be checked for before being called.
*
* If no such drop-in is available, this will call {@see WP_Fatal_Error_Handler::display_default_error_template()}.
*
* @since 5.2.0
*/
protected function display_error_template() {
if ( defined( 'WP_CONTENT_DIR' ) ) {
// Load custom PHP error template, if present.
$php_error_pluggable = WP_CONTENT_DIR . '/php-error.php';
if ( is_readable( $php_error_pluggable ) ) {
require_once $php_error_pluggable;
return;
}
}
// Otherwise, display the default error template.
$this->display_default_error_template();
}
/**
* Displays the default PHP error template.
*
* This method is called conditionally if no 'php-error.php' drop-in is available.
*
* It calls {@see wp_die()} with a message indicating that the site is experiencing technical difficulties and a
* login link to the admin backend. The {@see 'wp_php_error_message'} and {@see 'wp_php_error_args'} filters can
* be used to modify these parameters.
*
* @since 5.2.0
*/
protected function display_default_error_template() {
if ( ! function_exists( '__' ) ) {
wp_load_translations_early();
}
if ( ! function_exists( 'wp_die' ) ) {
require_once ABSPATH . WPINC . '/functions.php';
}
$message = __( 'The site is experiencing technical difficulties.' );
$args = array(
'response' => 500,
'exit' => false,
);
/**
* Filters the message that the default PHP error template displays.
*
* @since 5.2.0
*
* @param string $message HTML error message to display.
*/
$message = apply_filters( 'wp_php_error_message', $message );
/**
* Filters the arguments passed to {@see wp_die()} for the default PHP error template.
*
* @since 5.2.0
*
* @param array $args Associative array of arguments passed to `wp_die()`. By default these contain a
* 'response' key, and optionally 'link_url' and 'link_text' keys.
*/
$args = apply_filters( 'wp_php_error_args', $args );
$error = new WP_Error( 'internal_server_error', $message );
wp_die( $error, '', $args );
}
}

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@ -0,0 +1,54 @@
<?php
/**
* Error Protection API: Functions
*
* @package WordPress
* @since 5.2.0
*/
/**
* Registers the shutdown handler for fatal errors.
*
* The handler will only be registered if {@see wp_is_fatal_error_handler_enabled()} returns true.
*
* @since 5.2.0
*/
function wp_register_fatal_error_handler() {
if ( ! wp_is_fatal_error_handler_enabled() ) {
return;
}
$handler = null;
if ( defined( 'WP_CONTENT_DIR' ) && is_readable( WP_CONTENT_DIR . '/fatal-error-handler.php' ) ) {
$handler = include WP_CONTENT_DIR . '/fatal-error-handler.php';
}
if ( ! is_object( $handler ) || ! is_callable( array( $handler, 'handle' ) ) ) {
$handler = new WP_Fatal_Error_Handler();
}
register_shutdown_function( array( $handler, 'handle' ) );
}
/**
* Checks whether the fatal error handler is enabled.
*
* A constant `WP_DISABLE_FATAL_ERROR_HANDLER` can be set in `wp-config.php` to disable it, or alternatively the
* {@see 'wp_fatal_error_handler_enabled'} filter can be used to modify the return value.
*
* @since 5.2.0
*
* @return bool True if the fatal error handler is enabled, false otherwise.
*/
function wp_is_fatal_error_handler_enabled() {
$enabled = ! defined( 'WP_DISABLE_FATAL_ERROR_HANDLER' ) || ! WP_DISABLE_FATAL_ERROR_HANDLER;
/**
* Filters whether the fatal error handler is enabled.
*
* @since 5.2.0
*
* @param bool $enabled True if the fatal error handler is enabled, false otherwise.
*/
return apply_filters( 'wp_fatal_error_handler_enabled', $enabled );
}

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@ -17,9 +17,14 @@ define( 'WPINC', 'wp-includes' );
// Include files required for initialization.
require( ABSPATH . WPINC . '/load.php' );
require( ABSPATH . WPINC . '/class-wp-fatal-error-handler.php' );
require( ABSPATH . WPINC . '/error-protection.php' );
require( ABSPATH . WPINC . '/default-constants.php' );
require_once( ABSPATH . WPINC . '/plugin.php' );
// Make sure we register the shutdown handler for fatal errors as soon as possible.
wp_register_fatal_error_handler();
/*
* These can't be directly globalized in version.php. When updating,
* we're including version.php from another installation and don't want
@ -528,3 +533,12 @@ if ( is_multisite() ) {
* @since 3.0.0
*/
do_action( 'wp_loaded' );
/*
* Store the fact that we could successfully execute the entire WordPress
* lifecycle. This is used to skip the premature shutdown handler, as it cannot
* be unregistered.
*/
if ( ! defined( 'WP_EXECUTION_SUCCEEDED' ) ) {
define( 'WP_EXECUTION_SUCCEEDED', true );
}