Allow to return null on native cast

[rodrigopedra]

• Added or updated tests
• Added or updated the README.md
• Detailed changes in the CHANGELOG.md unreleased section

Related Issue/Intent

When using the native casting introduced in v2.0 I noticed that returning null from the parseDatabase method would result in error as it would still try to create an Enum instance from the returned value.

My use case is a modernization of a legacy codebase (25 years old) where some blank data is stored as empty strings instead of NULLs in the database.

So when running code like this:

public static function parseDatabase($value)
{
    if (\blank($value)) {
        return null;
    }

     return (int) $value;
}

Application would throw an exception on blank values (null or empty string).

For this particular project I ended adding a NA enum value and defaulting to that for blank values. This is not an ideal solution as the code that relies on the Enum value, and code to persist values back needs to take account of that.

Changes

This PR changes the Casts/EnumCast class to check for null values returned by userland code when using the parseDatabase method.

A new test was added. Test would fail without the changes introduced by this PR.

Breaking changes

No breaking changes.

[atymic]

Looks good to me. cc @BenSampo

[rodrigopedra]

Hi @atymic thanks for the quick assessment.

The library code on EnumCast checks specifically for nulls ($value === null), so if userland code returns, for example, 0 it would still be cast to an enum instance.

But the test class I updated (UserTypeCustomCast) allows for a falsy value for the Administrator enum value. Therefore the serializeDatabase in that example would fail for that value.

I will update both the test enum class and the test case.

UPDATE: no changes needed.

[BenSampo]

Cheers @rodrigopedra , I'll tag that now

[BenSampo]

@rodrigopedra I've tweaked the readme slightly, can you check that it still makes sense:

https://github.com/BenSampo/laravel-enum#casting-underlying-native-types

[rodrigopedra]

Thanks @BenSampo .

I saw the readme and your versions is much clearer, thanks again.