if this PR is accepted, we should also tackle the same errors in the phpstan extension repos, e.g. - anonymous class detection was fixed via b333809

1) Warning
The data provider specified for PHPStan\Type\Symfony\ExtensionTest::testFileAsserts is invalid.
File /home/runner/work/phpstan-src/phpstan-src/extension/tests/Type/Symfony/data/kernel_interface.php does not contain a namespace declaration

home/runner/work/phpstan-src/phpstan-src/extension/vendor/phpunit/phpunit/phpunit:60

The idea looks great to me! Is it possible to detect duplicate namespaces?

I think we could implement a phpstan collector to check for duplicate namespaces across all test files.

What I don't like with this PR is that it does not cover files e.g. included from Rule*Tests.
But maybe its still good enough for now as it discovered a lot of bugs already

something like https://github.com/slevomat/coding-standard/blob/master/doc/namespaces.md#slevomatcodingstandardnamespacesrequireonenamespaceinfile configured to run only in all test/*/data/* dirs or so could be a less aggressive alternative?

so could be a less aggressive alternative?

good idea.

what I like about this PR is, that it only enforces a namespace when you have named symbols contained.
therefore I was able to pinpoint which files are missing a namespace.

some tests might not have a namespace and adding one might imply changing a lot of test expectations (e.g. reported line numbers)

I don't think this is the right approach. We need something more general because:

1. There are also RuleTestCase child classes with the same requirement.
2. There's also LegacyNodeScopeResolverTest.

What would make more sense to me is a new workflow with a separate PHPStan config that would run PHPStan only on tests/*/data/* (which is currently excluded) and only with a custom ruleset with a few rules:

• Every file needs to have a namespace
• There cannot be duplicate functions and classes

Since that implementation is not going to have anything common with this PR, I'm closing it.

(If you want to send fixes for the discovered problems, sure, send a separate PR with no other changes :))