Ensure Dart1 and Dart2 can be used together

[zoechi]

From #31807

Will Dart2 run Dart1 programs or
will there be a way to have Dart1 and Dart2 installed at the same time?

@dgrove

The SDK is gradually moving to running Dart 2 only. As the SDK gets to Dart 2 only, you'd need a separate SDK installed to run Dart 1.

@zoechi

Don't you think this will cause issues if people use Dart apps that are not yet ported?
There can't be 2 dart.exe in the path at the same time.
Sorry for the noise in this thread, is it worth creating a new issue for that?

@dgrove

Can you open a new issue?

[matanlurey]

I don't understand this issue? You would need to have the Dart 1 SDK installed to run Dart 1 apps.

[natebosch]

Someone from the community could try making a dvm version manager helper to make it easier to have multiple SDKs on the same computer and switch between them.

I don't think we'll reasonably be able to keep dart 1 semantics around in the VM or elsewhere.

[zoechi]

@matanlurey sure, but how can I if both use dart.exe

I'd expect this to be easier if the Dart team considers it in the design.
There was and is a lot of work done to avoid breaking changes,
but then installing Dart2 on a system rendering all existing Dart1 tools unusable is just ignored.
That seems weird to me.

What about pub and dart.exe forwarding to Dart1 if it recognizes a Dart1 package or executable and the DART1_SDK_PATH env variable is set?

Just a first idea to initiate some brainstorming.

[matanlurey]

It's no different than if you started using a new language feature (like generic functions) on an older version of the SDK that couldn't parse/recognize it. While it's possible we could provide a convenience to forward to an older version of tooling, it's not likely this is something we'd do ourselves. The community of course is welcome!