Run non-null-safe tests with Dart 2

[kevmoo]

Move the non-null-safe usage of the API to another file, test the file with Dart 2.x.

[kevmoo]

Feel free to squash/merge and delete the branch if you're happy

[mraleph]

@osa1 I think this might be related to what you looked at today.

[osa1]

@kevmoo we've been discussing these tests in Dart Ecosystem chat. I don't think we want to remove these tests yet as internally we have non-null-safe Dart that uses this library.

[kevmoo]

@osa1 – but we can't run Dart 3.0.0- tests against this package w/ them there.

We could pull those out into another test file and only run them on stable or something 🤷

[osa1]

Right, I think we will need to move these to another file/package, and configure mono_repo to only test that package/file with SDK 2.x.

Apparently dart:test has a separate packages for legacy tests, for example https://github.com/dart-lang/test/blob/master/legacy_tests/spawn_hybrid_with_optout/pubspec.yaml. We could do the same. If we can specify running a specific file with a specific SDK in mono_repo.yaml we could also just move the file outside of test/ (maybe to legacy_test/), that would be simpler.

[kevmoo]

@osa1 – sure? Just trying to get CI to green so we can keep the signals of knowing when the SDK breaks things.

[osa1]

It seems like on CI dart analyze analyzes the new file. I don't understand why that happens, locally when I run dart analyze with Dart 3.0.x it doesn't analyze the new file.

We need to somehow make dart analyze skip the file with dev SDK.

[osa1]

LGTM now, but someone should review my mono_repo changes :-)

[devoncarew]

mono_repo changes and repo reconfiguration lgtm