ClassReflection: make getTraits recursive

[iamrgroot]

Changes the ClassReflection::getTraits function to be recursive according to the suggestion from @ondrejmirtes at larastan/larastan#837 (comment)

[ondrejmirtes]

This change needs a test.

[iamrgroot]

@ondrejmirtes should ClassReflection::getTraitNames also use ClassReflection::collectTraits?

In terms of tests needed: a test for the traits returned by ClassReflection::getTraits suffices or do you have more in mind? It's a bit difficult to dive into all of the test quickly.

[ondrejmirtes]

should ClassReflection::getTraitNames also use ClassReflection::collectTraits

Nope, that's only used in hasTraitUse() and that can stay non-recursive.

About the test for this PR - I'd like to have a new file in data directory next to ClassReflectionTest that adds some example classes with nested trait uses and then have a new testGetTraits() in ClassReflectionTest that checks that getTraits() returns the right thing.

You can obtain ClassReflection instance with this code in the test case:

$reflectionProvider = $this->createBroker();
$reflection = $reflectionProvider->getClass($className);

[iamrgroot]

@ondrejmirtes I've discovered that ClassReflection::collectTraits does not detect Traits that have been defined in parent classes. For example in my test case:

trait BazTrait
{
}

class Baz
{
    use BazTrait;
}

class BazChild extends Baz
{
}

($this->createBroker())->getClass(Baz::class)->getTraits() gives ['BazTrait']

($this->createBroker())->getClass(BazChild::class)->getTraits() gives []

Is this indended behavior? I noticed that if I change it to also include parent traits recursively, the following tests fail: AnnotationsPropertiesClassReflectionExtensionTest::testProperties, AnnotationsMethodsClassReflectionExtensionTest::testMethods, ClassReflectionTest::testClassHierarchyDistances. This is probably because of a different order in which the traits are discovered.

What is your take on this? For the Larastan use case, there is a function needed that just returns all traits for a class (and all of the parents).

[ondrejmirtes]

This is probably a sign we should care about backward compatibility more (when it even breaks PHPStan internals). So I suggest this:

1. Add getTraits(bool $recursive = false) optional parameter
2. Test behaviour of both getTraits(true) and getTraits(false).
3. Change Larastan so that it uses getTraits(true).
4. In 1.0 myself I'll change this API to something nicer - like getTraits() (recursive) and getImmediateTraits() (current behaviour of getTraits().

[dktapps]

What about adding a getTraitsRecursive() method? It would be more self-documenting than an opaque boolean parameter.

[ondrejmirtes]

This is just a temporary measure, I'll do something cleaner in 1.0.

[ondrejmirtes]

Thank you!