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PhutilErrorHandler.php
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Mon, Jan 27, 19:53

PhutilErrorHandler.php
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<?php
/**
* Improve PHP error logs and optionally route errors, exceptions and debugging
* information to a central listener.
*
* This class takes over the PHP error and exception handlers when you call
* ##PhutilErrorHandler::initialize()## and forwards all debugging information
* to a listener you install with ##PhutilErrorHandler::setErrorListener()##.
*
* To use PhutilErrorHandler, which will enhance the messages printed to the
* PHP error log, just initialize it:
*
* PhutilErrorHandler::initialize();
*
* This will also enable @{function:phlog}, for printing development debugging
* messages.
*
* To additionally install a custom listener which can print error information
* to some other file or console, register a listener:
*
* PhutilErrorHandler::setErrorListener($some_callback);
*
* For information on writing an error listener, see
* @{function:phutil_error_listener_example}. Providing a listener is optional,
* you will benefit from improved error logs even without one.
*
* Phabricator uses this class to drive the DarkConsole "Error Log" plugin.
*
* @task config Configuring Error Dispatch
* @task exutil Exception Utilities
* @task internal Internals
* @group error
*/
final class PhutilErrorHandler {
private static $errorListener = null;
private static $initialized = false;
const EXCEPTION = 'exception';
const ERROR = 'error';
const PHLOG = 'phlog';
const DEPRECATED = 'deprecated';
/* -( Configuring Error Dispatch )----------------------------------------- */
/**
* Registers this class as the PHP error and exception handler. This will
* overwrite any previous handlers!
*
* @return void
* @task config
*/
public static function initialize() {
self::$initialized = true;
set_error_handler(array('PhutilErrorHandler', 'handleError'));
set_exception_handler(array('PhutilErrorHandler', 'handleException'));
}
/**
* Provide an optional listener callback which will receive all errors,
* exceptions and debugging messages. It can then print them to a web console,
* for example.
*
* See @{function:phutil_error_listener_example} for details about the
* callback parameters and operation.
*
* @return void
* @task config
*/
public static function setErrorListener($listener) {
self::$errorListener = $listener;
}
/* -( Exception Utilities )------------------------------------------------ */
/**
* Gets the previous exception of a nested exception. Prior to PHP 5.3 you
* can use @{class:PhutilProxyException} to nest exceptions; after PHP 5.3
* all exceptions are nestable.
*
* @param Exception Exception to unnest.
* @return Exception|null Previous exception, if one exists.
* @task exutil
*/
public static function getPreviousException(Exception $ex) {
if (method_exists($ex, 'getPrevious')) {
return $ex->getPrevious();
}
if (method_exists($ex, 'getPreviousException')) {
return $ex->getPreviousException();
}
return null;
}
/**
* Find the most deeply nested exception from a possibly-nested exception.
*
* @param Exception A possibly-nested exception.
* @return Exception Deepest exception in the nest.
* @task exutil
*/
public static function getRootException(Exception $ex) {
$root = $ex;
while (self::getPreviousException($root)) {
$root = self::getPreviousException($root);
}
return $root;
}
/* -( Internals )---------------------------------------------------------- */
/**
* Determine if PhutilErrorHandler has been initialized.
*
* @return bool True if initialized.
* @task internal
*/
public static function hasInitialized() {
return self::$initialized;
}
/**
* Handles PHP errors and dispatches them forward. This is a callback for
* ##set_error_handler()##. You should not call this function directly; use
* @{function:phlog} to print debugging messages or ##trigger_error()## to
* trigger PHP errors.
*
* This handler converts E_RECOVERABLE_ERROR messages from violated typehints
* into @{class:InvalidArgumentException}s.
*
* This handler converts other E_RECOVERABLE_ERRORs into
* @{class:RuntimeException}s.
*
* This handler converts E_NOTICE messages from uses of undefined variables
* into @{class:RuntimeException}s.
*
* @param int Error code.
* @param string Error message.
* @param string File where the error occurred.
* @param int Line on which the error occurred.
* @param wild Error context information.
* @return void
* @task internal
*/
public static function handleError($num, $str, $file, $line, $ctx) {
if ((error_reporting() & $num) == 0) {
// Respect the use of "@" to silence warnings: if this error was
// emitted from a context where "@" was in effect, the
// value returned by error_reporting() will be 0. This is the
// recommended way to check for this, see set_error_handler() docs
// on php.net.
return false;
}
// Convert typehint failures into exceptions.
if (preg_match('/^Argument (\d+) passed to (\S+) must be/', $str)) {
throw new InvalidArgumentException($str);
}
// Convert other E_RECOVERABLE_ERRORs into generic runtime exceptions.
if ($num == E_RECOVERABLE_ERROR) {
throw new RuntimeException($str);
}
// Convert uses of undefined variables into exceptions.
if (preg_match('/^Undefined variable: /', $str)) {
throw new RuntimeException($str);
}
// Convert uses of undefined properties into exceptions.
if (preg_match('/^Undefined property: /', $str)) {
throw new RuntimeException($str);
}
$trace = debug_backtrace();
array_shift($trace);
self::dispatchErrorMessage(
self::ERROR,
$str,
array(
'file' => $file,
'line' => $line,
'context' => $ctx,
'error_code' => $num,
'trace' => $trace,
));
}
/**
* Handles PHP exceptions and dispatches them forward. This is a callback for
* ##set_exception_handler()##. You should not call this function directly;
* to print exceptions, pass the exception object to @{function:phlog}.
*
* @param Exception Uncaught exception object.
* @return void
* @task internal
*/
public static function handleException(Exception $ex) {
self::dispatchErrorMessage(
self::EXCEPTION,
$ex,
array(
'file' => $ex->getFile(),
'line' => $ex->getLine(),
'trace' => self::getRootException($ex)->getTrace(),
'catch_trace' => debug_backtrace(),
));
// Normally, PHP exits with code 255 after an uncaught exception is thrown.
// However, if we install an exception handler (as we have here), it exits
// with code 0 instead. Script execution terminates after this function
// exits in either case, so exit explicitly with the correct exit code.
exit(255);
}
/**
* Output a stacktrace to the PHP error log.
*
* @param trace A stacktrace, e.g. from debug_backtrace();
* @return void
* @task internal
*/
public static function outputStacktrace($trace) {
$lines = explode("\n", self::formatStacktrace($trace));
foreach ($lines as $line) {
error_log($line);
}
}
/**
* Format a stacktrace for output.
*
* @param trace A stacktrace, e.g. from debug_backtrace();
* @return string Human-readable trace.
* @task internal
*/
public static function formatStacktrace($trace) {
$result = array();
foreach ($trace as $key => $entry) {
$line = ' #'.$key.' ';
if (isset($entry['class'])) {
$line .= $entry['class'].'::';
}
$line .= idx($entry, 'function', '');
if (isset($entry['args'])) {
$args = array();
foreach ($entry['args'] as $arg) {
$args[] = PhutilReadableSerializer::printShort($arg);
}
$line .= '('.implode(', ', $args).')';
}
if (isset($entry['file'])) {
$line .= ' called at ['.$entry['file'].':'.$entry['line'].']';
}
$result[] = $line;
}
return implode("\n", $result);
}
/**
* All different types of error messages come here before they are
* dispatched to the listener; this method also prints them to the PHP error
* log.
*
* @param const Event type constant.
* @param wild Event value.
* @param dict Event metadata.
* @return void
* @task internal
*/
public static function dispatchErrorMessage($event, $value, $metadata) {
$timestamp = strftime("%F %T");
switch ($event) {
case PhutilErrorHandler::ERROR:
$default_message = sprintf(
'[%s] ERROR %d: %s at [%s:%d]',
$timestamp,
$metadata['error_code'],
$value,
$metadata['file'],
$metadata['line']);
$metadata['default_message'] = $default_message;
error_log($default_message);
self::outputStacktrace($metadata['trace']);
break;
case PhutilErrorHandler::EXCEPTION:
$messages = array();
$current = $value;
do {
$messages[] = '('.get_class($current).') '.$current->getMessage();
} while ($current = self::getPreviousException($current));
$messages = implode(' {>} ', $messages);
if (strlen($messages) > 4096) {
$messages = substr($messages, 0, 4096).'...';
}
$default_message = sprintf(
'[%s] EXCEPTION: %s at [%s:%d]',
$timestamp,
$messages,
self::getRootException($value)->getFile(),
self::getRootException($value)->getLine());
$metadata['default_message'] = $default_message;
error_log($default_message);
self::outputStacktrace(self::getRootException($value)->getTrace());
break;
case PhutilErrorHandler::PHLOG:
$default_message = sprintf(
'[%s] PHLOG: %s at [%s:%d]',
$timestamp,
PhutilReadableSerializer::printShort($value),
$metadata['file'],
$metadata['line']);
$metadata['default_message'] = $default_message;
error_log($default_message);
break;
case PhutilErrorHandler::DEPRECATED:
$default_message = sprintf(
'[%s] DEPRECATED: %s is deprecated; %s',
$timestamp,
$value,
$metadata['why']);
$metadata['default_message'] = $default_message;
error_log($default_message);
break;
default:
error_log('Unknown event '.$event);
break;
}
if (self::$errorListener) {
static $handling_error;
if ($handling_error) {
error_log(
"Error handler was reentered, some errors were not passed to the ".
"listener.");
return;
}
$handling_error = true;
call_user_func(self::$errorListener, $event, $value, $metadata);
$handling_error = false;
}
}
}

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