Do not use null as default value

[VincentLanglet]

Subject

I am targeting this branch, because BC.

getOptions is using array_key_exist so

$this->getOptions('field_type', DateTimeFilter::class)

will return null instead of DateTimeFiler::class when the type is guessed by our guesser.

This issue was reported on slack by someone using the master branch and he tried the fix for me.

Changelog

### Fixed
- Do not provide a default `null` `field_type` option for Filter

[franmomu]

Looks like the problem is that field_type is not defined in

SonataDoctrineORMAdminBundle/src/Guesser/FilterTypeGuesser.php

Lines 90 to 98 in 4098faf

	case 'datetime':
	case 'datetime_immutable':
	case 'vardatetime':
	case 'datetimetz':
	case 'datetimetz_immutable':
	return new TypeGuess(DateTimeFilter::class, $options, Guess::HIGH_CONFIDENCE);
	case 'date':
	case 'date_immutable':
	return new TypeGuess(DateFilter::class, $options, Guess::HIGH_CONFIDENCE);

I guess the $options['field_type]` should be added in both cases.

Either way, IMO a test should be added.

[VincentLanglet]

Looks like the problem is that field_type is not defined in

SonataDoctrineORMAdminBundle/src/Guesser/FilterTypeGuesser.php

Lines 90 to 98 in 4098faf

	case 'datetime':
	case 'datetime_immutable':
	case 'vardatetime':
	case 'datetimetz':
	case 'datetimetz_immutable':
	return new TypeGuess(DateTimeFilter::class, $options, Guess::HIGH_CONFIDENCE);
	case 'date':
	case 'date_immutable':
	return new TypeGuess(DateFilter::class, $options, Guess::HIGH_CONFIDENCE);

I guess the $options['field_type]` should be added in both cases.

It should instead rely on the default value like here: https://github.com/sonata-project/SonataDoctrineORMAdminBundle/blob/3.x/src/Filter/DateFilter.php#L39

There is no reason to set null, instead we should set nothing and let the filter doing his work.

[franmomu]

So, should we remove the rest of field_type from there?

[VincentLanglet]

So, should we remove the rest of field_type from there?

That's a good point.

Other filters are setting the field_type because they were no default one.

For instance, the NumberFilter is not overriding the getFieldType method

    public function getFieldType()
    {
        return $this->getOption('field_type', TextType::class);
    }

I'll fix this.

[VincentLanglet]

By the way, in SonataAdmin we're not using getFieldType and getFieldOption so this could be removed from the FilterInterface.

[VincentLanglet]

@franmomu Tests are updated to check that null is not passed.
And I removed the useless field_type.