Laravel OAuth2 Password Grant getClientStorage is null

I am creating a RESTful Laravel 5.1 API, and only have one client static site accessing the API. I wanted to add OAuth2 to protect the routes, so I went with lucadegasperi's OAuth2.

Making a request for access token, I get

{
   "error": "invalid_client",
   "error_description": "Client authentication failed."
}

With credentials (Making a DHC post request to http://ift.tt/1EjUjO3):

{  
  "grant_type" : "password",
  "username" : "myname",
  "password" : "password",
  "client_id" : "webapp",
  "client_secret" : "123"
}

I've followed the PasswordGrantVerifier docs to set this up, and added that codeblock to my \App namespace, and set up my oauth2.php config as such:

'grant_types' => [
    'password' => [
        'class' => '\League\OAuth2\Server\Grant\PasswordGrant',
        'callback' => '\App\PasswordGrantVerifier@verify',
        'access_token_ttl' => 3600
    ]
],

I looked into this exception, and traced it to PasswordGrant.php, namely:

    $clientId = $this->server->getRequest()->request->get('client_id', $this->server->getRequest()->getUser());
    if (is_null($clientId)) {
        throw new Exception\InvalidRequestException('client_id');
    }

    //die($clientId) gives "webapp"

    $clientSecret = $this->server->getRequest()->request->get('client_secret',
        $this->server->getRequest()->getPassword());
    if (is_null($clientSecret)) {
        throw new Exception\InvalidRequestException('client_secret');
    }

    //die($clientSecret) gives "123"

    // THE ERROR IS HERE
    $client = $this->server->getClientStorage()->get(
        $clientId,
        $clientSecret,
        null,
        $this->getIdentifier()
    );
    dd($client); // NULL

The $client is null, but when I died my $clientId and $clientSecret above, they were correct. Likewise, I've already added a test client to my oauth_clients table.

I traced this back further to check out getClientStorage() within AbstractServer.php, and checked where client storage was set in setClientStorage().

What is happening here?

via Chebli Mohamed