Throwing an exception in acquireLock(...) fails

[sukovf]

Version: 2.10 PHP: 8.0.3

Bug Description

Throwing an exception at Engine.php:247 fails as Latte expects the function error_get_last() to always return an array from what it tries to read the message key. However, the aforementioned function can also return NULL, see https://www.php.net/manual/en/function.error-get-last.php

throw new RuntimeException("Unable to create directory '$dir'. " . error_get_last()['message']);

Steps To Reproduce

set_error_handler('myErrorHandler');// <- this is what makes the error_get_last() func to always return NULL instead of an array
$latte = new Latte\Engine();
$latte->setTempDirectory('temp');// <- make sure your app can't access or make that dir!!!
$output = $latte->renderToString('random_template.latte');

[dg]

I expect if mkdir() returns false, then error_get_last() will return last error. Under what circumstances does it fail?

[sukovf]

It's a very simple Slim2-based app but I see the problem now: If you set a custom error handler through the set_error_handler(...) function (Slim2 does that by default), then the error_get_last() function always returns NULL.

EDIT: I've updated the Steps To Reproduce section in my original post.

[dakujem]

👉 @ Error Suppression operator does not silent fatal errors

This dirty draft fixes it for me.

    private function isExpired(string $file, string $name): bool
    {
        try {
            return $this->autoRefresh && $this->getLoader()->isExpired($name, (int)@filemtime($file)); // @ - file may not exist
        } catch (ErrorException $e) {
            return $this->getLoader()->isExpired($name, 0);
        }
    }

Please fix asap.

PHP 8.0.3 , built-in server, Windows.

[dakujem]

I have to add that in my project setup, all errors, notices and warnings are turned into an ErrorException. I'm not completely sure if this is anyhow related or not.

[dg]

@dakujem yes, it is related, simply don't do it. And your issue is completely unrelated to @sukovf issue and to "Error Suppression operator does not silent fatal errors".

@sukovf custom error handler should returns false to fill-in error_get_last()

[sukovf]

@dg I'm not sure if I understand what you mean. The custom error handling function in Slim2 doesn't return anything, it just throws an exception built upon the data of catched PHP errors. Yes I can override that error handler but I think it's generally not a good idea to treat the output of a function directly as an array while it can also return NULL.

EDIT: Hmm whenever an exception is thrown, the code execution should stop and never reach the point when the func error_get_last() is called. Weird...

[mabar]

error_get_last() returns null only in case of no error and when the error is removed by error_clear_last() or by (incorrectly implemented) error handler. It's generally reliable behavior with exception of some functions which can fail without creating an error (like mail()). In this case, it's error handler failure - it should return false, because it didn't handle error.

[dg]

@sukovf in Slim2 error handler is bug, there https://github.com/slimphp/Slim/blob/7d3308bb8b41238941c0cbf549ef103c1bd69a30/Slim/Slim.php#L1407 should be return false. Without false it completely disables the function error_get_last().

It's weird PHP behavior, but there's nothing we can do about it.

https://phpfashion.com/how-to-write-error-handler-in-php

[sukovf]

@dg Yep I see it now thanks to @mabar (y). It's time to finally convince my colleagues to upgrade. Thanks for your time.

[dg]

Or you can set your custom and fixed error handler.

[dakujem]

@sukovf to clarify the previous answers, you only need to return false instead of return; (null) at the line David posted above. The most trivial and striaght-forward way to do this would be by extending the Slim\Slim class to override the handleErrors method.

// for Slim v2
class MySlimApp extends \Slim\Slim
{
    public static function handleErrors($errno, $errstr = '', $errfile = '', $errline = '')
    {
        if (!($errno & error_reporting())) {
            return false; // <--- Note the returned false here
        }
        throw new \ErrorException($errstr, $errno, 0, $errfile, $errline);
    }
}

[dakujem]

@dg The issue I'm facing is not completely unrelated. It's related to error suppression using @ which temporarily changes the error-reporting level. Given an incorrect error handler, this breaks Latte (and undoubtfully other code using @).

I was using error handler for PHP 7, which stopped working after the upgrade to PHP 8. I'm including this for sake of other people who stumble upon the same/similar issue.

set_error_handler(function ($errno, $errstr, $errfile, $errline) {
    // WARNING: DO NOT DO THIS kind of comparison, it fails in PHP 8+
    if (0 === error_reporting()) {
        // error was suppressed with the @-operator (only works until PHP 7.4)
        return false;
    }
    throw new ErrorException($errstr, 0, $errno, $errfile, $errline);
});

I believe this snippet comes from some older Slim tutorial or similar resource.

[dg]

I wrote it down here https://phpfashion.com/how-to-write-error-handler-in-php