ImpersonatedServiceAccountCredentials: cache config is null

[lukasamd]

Environment details

• OS: Debian 12
• PHP version: 8.4.3
• Package name and version: googleapis/google-auth-library-php 1.46.0

Steps to reproduce

I wanted to use storage from local with impersonated service account - logged into GCP, then generated application_default_credential.json using impersonated SA, but with PHP, I have a problem. Operations works fine, but there is warning:

( ! ) Warning: Trying to access array offset on null in vendor/google/auth/src/CacheTrait.php on line 98

and related code:

$key = $this->cacheConfig['prefix'] . $key;

I've checked code and it makes sense. ImpersonatedServiceAccountCredentials class uses this trait, but does not configure cacheConfig. Looks like it should be injected to fetcher from FetchAuthTokenCache

Code example

require 'vendor/autoload.php';

use Google\Cloud\Storage\StorageClient;

$storage = new StorageClient();

$bucketName = 'some-test-bucket';
$objectName = 'some-test-object';
$content = 'Test content.';

try {
    $bucket = $storage->bucket($bucketName);
    $object = $bucket->upload($content, ['name' => $objectName]);
    echo "Object $objectName uploaded successfully.\n";
} catch (\Google\Cloud\Core\Exception\ServiceException $e) {
    echo 'Caught exception: ', $e->getMessage(), "\n";
}

Example fix

Just very quick, should be adjusted for rest:

ImpersonatedServiceAccountCredentials - add cache config setter

    public function setCacheConfig(?array $config) 
    {
        $this->cacheConfig = (array) $config;
    }

Then FetchAuthTokenCache, pass cache config to fetcher in constructor:

    public function __construct(
        FetchAuthTokenInterface $fetcher,
        ?array $cacheConfig = null,
        ?CacheItemPoolInterface $cache = null
    ) {
        $this->fetcher = $fetcher;
        $this->cache = $cache;
        $this->cacheConfig = array_merge([
            'lifetime' => 1500,
            'prefix' => '',
            'cacheUniverseDomain' => $fetcher instanceof Credentials\GCECredentials,
        ], (array) $cacheConfig);
        
        $this->fetcher->setCacheConfig($this->cacheConfig);
    }