Validation of `[]` for type `map` with all fields optional will fail

[LoogleCZ]

Description

Data type map does not work as expected when all fields are optional and I submit empty array for validation. See steps to reproduce for more details. I expected that this will be valid.

Steps to reproduce

If I will use following schema for validator:

$schema = [
    'type' => 'map',
    'properties' => [
        'test' => [
            'enum' => [
                "val1",
                true,
                "415646",
            ],
            'optional' => true,
        ],
    ],
];

$validator = new Validator($schema);

and then call

$res = $schema->validate([]);
var_dump($res->getErrors());

I will get "Wrong data type in '/'; expected 'map'; got 'array'"

Suggested fix

1. Update Validator::validate to handle empty array as map as well as array
2. use oneOf directive over schema (have not tried).

First approach makes more sence for me.

PS: I can fix this issue and propose PR to schematicon/validator-php repo. This PR will come probably in next week if approved

[hrach]

Thanks for great bug report. :)