Laravel regex validation for empty string - regex

Question

I have the following validation,
it should match string with letters,numbers,dashes. And empty input should also be valid.
The normal string validation is ok, but I can not make it match "empty" input.
'letter_code' => 'regex:/^[A-Za-z0-9\-]*$/'
letter_code format is invalid
tests:
"C14" // valid
"3.14" // "format is invalid", as expected
"-" // valid
"" // "format is invalid", NOT expected

Answer 1

I just found out in laracasts forum, that there is a nullable rule.
You can read about it in the official docs.
Without the nullable rule empty strings are considered invalid if there is a regex rule as well.

Answer 2

If you don't add required as additional validator empty string must pass
Here is phpunit test:
/** #test */
public function letterCode()
{
$trans = new \Illuminate\Translation\Translator(
new \Illuminate\Translation\ArrayLoader, 'en'
);
$regex = 'regex:/^[A-Za-z0-9\-]*$/';
$v = new Validator($trans, ['x' => 'C14'], ['x' => $regex]);
$this->assertTrue($v->passes());
$v = new Validator($trans, ['x' => '3.14'], ['x' => $regex]);
$this->assertFalse($v->passes());
$v = new Validator($trans, ['x' => '-'], ['x' => $regex]);
$this->assertTrue($v->passes());
$v = new Validator($trans, ['x' => ''], ['x' => $regex]);
$this->assertTrue($v->passes());
}
This is tested with Laravel 5.5

Answer 3

I was facing the same problem in Laravel 7.x using GraphQL Types. I needed something similar to this in a field called phone or nothig (empty string). So I did something like this:
'phone' => [
'name' => 'phone',
'type' => Type::string(),
'rules' => ['regex:/^[A-Za-z0-9\-]*$/','nullable']
Here, phone is the name of the field you want to enter text into, and rules is what we define as regex, or NULL.
Hope this helps someone!