Exception thrown when Mobile_Detect return `null` as user agent

[fratsloos]

In some cases I see the following log in my Laravel logs:

[2023-06-11 03:51:45] live.ERROR: Spinen\BrowserFilter\Support\ParserCreator::parseAgent(): Argument #1 ($agent) must be of type string, null given, called in /path/to/vendor/spinen/laravel-browser-filter/src/Filter.php on line 56 {"url":"https://website.com","method":"GET","exception":"[object] (TypeError(code: 0): Spinen\\BrowserFilter\\Support\\ParserCreator::parseAgent(): Argument #1 ($agent) must be of type string, null given, called in /path/to/vendor/spinen/laravel-browser-filter/src/Filter.php on line 56 at /path/to/vendor/spinen/laravel-browser-filter/src/Support/ParserCreator.php:32)
[stacktrace]
#0 /path/to/vendor/spinen/laravel-browser-filter/src/Filter.php(56): Spinen\\BrowserFilter\\Support\\ParserCreator->parseAgent()
#1 [internal function]: Spinen\\BrowserFilter\\Filter->__construct()
#2 /path/to/vendor/laravel/framework/src/Illuminate/Container/Container.php(954): ReflectionClass->newInstanceArgs()
#3 /path/to/vendor/laravel/framework/src/Illuminate/Container/Container.php(795): Illuminate\\Container\\Container->build()
#4 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Application.php(933): Illuminate\\Container\\Container->resolve()
#5 /path/to/vendor/laravel/framework/src/Illuminate/Container/Container.php(731): Illuminate\\Foundation\\Application->resolve()
#6 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Application.php(918): Illuminate\\Container\\Container->make()
#7 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(169): Illuminate\\Foundation\\Application->make()
#8 /path/to/vendor/laravel/framework/src/Illuminate/Routing/Middleware/SubstituteBindings.php(50): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#9 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Routing\\Middleware\\SubstituteBindings->handle()
#10 /path/to/vendor/laravel/framework/src/Illuminate/Session/Middleware/AuthenticateSession.php(41): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#11 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Session\\Middleware\\AuthenticateSession->handle()
#12 /path/to/vendor/laravel/framework/src/Illuminate/View/Middleware/ShareErrorsFromSession.php(49): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#13 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\View\\Middleware\\ShareErrorsFromSession->handle()
#14 /path/to/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(121): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#15 /path/to/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(64): Illuminate\\Session\\Middleware\\StartSession->handleStatefulRequest()
#16 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Session\\Middleware\\StartSession->handle()
#17 /path/to/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php(37): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#18 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Cookie\\Middleware\\AddQueuedCookiesToResponse->handle()
#19 /path/to/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php(67): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#20 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Cookie\\Middleware\\EncryptCookies->handle()
#21 /path/to/app/Http/Middleware/Auth/ValidateForExtendedSessions.php(24): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#22 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): App\\Http\\Middleware\\Auth\\ValidateForExtendedSessions->handle()
#23 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(116): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#24 /path/to/vendor/laravel/framework/src/Illuminate/Routing/Router.php(798): Illuminate\\Pipeline\\Pipeline->then()
#25 /path/to/vendor/laravel/framework/src/Illuminate/Routing/Router.php(777): Illuminate\\Routing\\Router->runRouteWithinStack()
#26 /path/to/vendor/laravel/framework/src/Illuminate/Routing/Router.php(741): Illuminate\\Routing\\Router->runRoute()
#27 /path/to/vendor/laravel/framework/src/Illuminate/Routing/Router.php(730): Illuminate\\Routing\\Router->dispatchToRoute()
#28 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(200): Illuminate\\Routing\\Router->dispatch()
#29 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(141): Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}()
#30 /path/to/vendor/livewire/livewire/src/DisableBrowserCache.php(19): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#31 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Livewire\\DisableBrowserCache->handle()
#32 /path/to/vendor/laravel/framework/src/Illuminate/Http/Middleware/TrustProxies.php(39): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#33 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Http\\Middleware\\TrustProxies->handle()
#34 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#35 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ConvertEmptyStringsToNull.php(31): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#36 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\ConvertEmptyStringsToNull->handle()
#37 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#38 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TrimStrings.php(40): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle()
#39 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\TrimStrings->handle()
#40 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ValidatePostSize.php(27): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#41 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\ValidatePostSize->handle()
#42 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/PreventRequestsDuringMaintenance.php(86): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#43 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(180): Illuminate\\Foundation\\Http\\Middleware\\PreventRequestsDuringMaintenance->handle()
#44 /path/to/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(116): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}()
#45 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(175): Illuminate\\Pipeline\\Pipeline->then()
#46 /path/to/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(144): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter()
#47 /path/to/public/index.php(51): Illuminate\\Foundation\\Http\\Kernel->handle()
#48 {main}
"}

It appears that the method getUserAgent of Mobile_Detect returns null, which is correct according to the docbloc of the method, while parseAgent in ParserCreator expects a string. Based on the logs I'm not able to recreate the request which caused it. There is no request logged in the access_log on the same time, but before and after the time of the Laravel log I see some activity from the Bing bot.

As I can't reproduce the request it's kind of hard to find the exact reason why this fails. Therefore I did not create a PR. My suggestion for a fix is to check the user agent first in the constructor of Filter.php and then check it in validateRules:

abstract class Filter
{
    public function __construct(
        protected Cache $cache,
        protected Config $config,
        protected Mobile_Detect $detector,
        protected ParserCreator $parser,
        protected Redirector $redirector
    ) {
        $userAgent = $detector->getUserAgent();
        $this->client = !is_null($userAgent)
            ? $parser->parseAgent($userAgent)
            : null;
    }

    public function validateRules(): void
    {
        if (is_null($this->client) || empty($this->getRules())) {
            return;
        }

        foreach ($this->getRules() as $device => $browsers) {
            $this->validDeviceRule($device, $browsers);
        }
    }
}

But as said, because I can't recreate the request I cannot test this solution.

I'm using version 3.1.0 of this package with PHP 8.2.