explicitly use 0 instead of adding null

Author: dbu

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - Test with PHP 8.1 and 8.2
 - Made phpspec tests compatible with PSR-7 2.0 strict typing
+- Detect `null` and use 0 explicitly to calculate expiration
 
 ## 1.7.5 - 2022-01-18
 

src/CachePlugin.php

@@ -230,7 +230,7 @@ private function calculateCacheItemExpiresAfter(?int $maxAge): ?int
             return null;
         }
 
-        return $this->config['cache_lifetime'] + $maxAge;
+        return ($this->config['cache_lifetime'] ?: 0) + ($maxAge ?: 0);
     }
 
     /**
@@ -368,7 +368,7 @@ private function configureOptions(OptionsResolver $resolver): void
         $resolver->setAllowedTypes('default_ttl', ['int', 'null']);
         $resolver->setAllowedTypes('respect_cache_headers', ['bool', 'null']);
         $resolver->setAllowedTypes('methods', 'array');
-        $resolver->setAllowedTypes('cache_key_generator', ['null', 'Http\Client\Common\Plugin\Cache\Generator\CacheKeyGenerator']);
+        $resolver->setAllowedTypes('cache_key_generator', ['null', CacheKeyGenerator::class]);
         $resolver->setAllowedTypes('blacklisted_paths', 'array');
         $resolver->setAllowedValues('hash_algo', hash_algos());
         $resolver->setAllowedValues('methods', function ($value) {