[VarDumper] Support for ReflectionAttribute

[derrabus]

Q	A
Branch?	master
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	N/A
License	MIT
Doc PR	not needed

VarDumper currently does not understand that certain reflection objects might have attributes attached to it. Dumping a ReflectionAttribute just yields ReflectionAttribute {#4711} which is not really helpful. This PR attempts to fix this.

ReflectionAttribute {#4711
  name: "App\MyAttribute"
  arguments: array:2 [
    0 => "one"
    "extra" => "hello"
  ]
}

While working on this, I noticed that class constants (which can be reflected on since PHP 7.1) are just dumped as plain values, so I've also added a caster for ReflectionClasConstant as bonus.

The full output for the LotsOfAttributes fixture class that is included with is PR looks like this:

^ ReflectionClass {#7
  +name: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
  modifiers: "final"
  implements: []
  constants: array:1 [
    0 => ReflectionClassConstant {#20
      +name: "SOME_CONSTANT"
      +class: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
      modifiers: "public"
      value: "some value"
      attributes: array:2 [
        0 => ReflectionAttribute {#33
          name: "Symfony\Component\VarDumper\Tests\Fixtures\RepeatableAttribute"
          arguments: array:1 [
            0 => "one"
          ]
        }
        1 => ReflectionAttribute {#34
          name: "Symfony\Component\VarDumper\Tests\Fixtures\RepeatableAttribute"
          arguments: array:1 [
            0 => "two"
          ]
        }
      ]
    }
  ]
  properties: array:1 [
    "someProperty" => ReflectionProperty {#19
      +name: "someProperty"
      +class: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
      modifiers: "private"
      attributes: array:1 [
        0 => ReflectionAttribute {#30
          name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
          arguments: array:2 [
            0 => "one"
            "extra" => "hello"
          ]
        }
      ]
    }
  ]
  methods: array:1 [
    "someMethod" => ReflectionMethod {#21
      +name: "someMethod"
      +class: "Symfony\Component\VarDumper\Tests\Fixtures\LotsOfAttributes"
      returnType: "void"
      parameters: {
        $someParameter: ReflectionParameter {#28
          +name: "someParameter"
          position: 0
          attributes: array:1 [
            0 => ReflectionAttribute {#42
              name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
              arguments: array:1 [
                0 => "three"
              ]
            }
          ]
          typeHint: "string"
        }
      }
      attributes: array:1 [
        0 => ReflectionAttribute {#27
          name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
          arguments: array:1 [
            0 => "two"
          ]
        }
      ]
      modifiers: "public"
    }
  ]
  attributes: array:1 [
    0 => ReflectionAttribute {#22
      name: "Symfony\Component\VarDumper\Tests\Fixtures\MyAttribute"
      arguments: []
    }
  ]
  extra: {
    file: "./src/Symfony/Component/VarDumper/Tests/Fixtures/LotsOfAttributes.php"
    line: "15 to 28"
    isUserDefined: true
  }
}

[derrabus]

💡 It felt a bit odd that I needed to do this, so I've opened https://bugs.php.net/bug.php?id=80097 for clarification.

[derrabus]

The segfault that be observed in https://travis-ci.org/github/symfony/symfony/jobs/726646852 (line 3655) appeared after my changes to the ReflectionCaster class. I can reproduce it locally (php 8.0 67d21bf237 on macOS 10.15) by just executing

./phpunit src/Symfony/Component/VarDumper/Tests/Caster/ReflectionCasterTest.php

But when I rerun that command a couple of times, it eventually works and the tests pass. I haven't been able to isolate the problem yet, but maybe this is an interesting find for @nikic or @beberlei that helps with stabilizing the reflection API for attributes.

[beberlei]

Do you have the stacktrace for the segfault?

[nicolas-grekas]

Thanks for the PR.
This should target master to me, as I have this rule in mind:

• making existing code run on newest PHP versions should be considered as a bug fix
• making Symfony compatible with new features of the language should be considered as a new feature.

[derrabus]

I use the dump() function a lot when debugging on php 8 because I don't have a working PhpStorm/Xdebug-Setup for php 8 yet. It would be extremely helpful to be able to see attributes in the dumped output. But I understand that the policy you mentioned also applies to VarDumper, so I'm going to rebase the PR on master.

[nicolas-grekas]

with minor comments

[nicolas-grekas]

with minor comments

[nicolas-grekas]

for .github/patch-types.php:
src/Symfony/Component/VarDumper/Tests/Fixtures/MyAttribute.php

[fabpot]

Thank you @derrabus.