Multiplatform capabilities broken

[thebarndog]

What happened?

The multiplatform fixtures seem to be broken, in particular multiplatform_app_with_sdk. I was building something similar on by own and encountered this error:

We received an error that we couldn't handle:
    - Localized description: The operation couldn’t be completed. (TuistKit.UnspecifiedPlatformError error 1.)
    - Error: Only single platform targets supported. The target DataModels specifies multiple supported platforms (watchos, ios).

When trying to run tuist build on the multiplatform fixture, I encountered the same error. Doesn't seem to be tied to a specific version of Tuist; the fixture uses 3.4.0 and I was using 4.0.0, same issue. If this is a real issue and not something simple I'm missing, I suspect it hasn't been found because it's rare to have multiple platforms for the same app within a project, necessitating a multiplatform framework.

How do we reproduce it?

1. Run tuist build on the multiplatform_app_with_sdk fixture
2. Observe build error

Error log

We received an error that we couldn't handle:
- Localized description: The operation couldn’t be completed. (TuistKit.UnspecifiedPlatformError error 1.)
- Error: Only single platform targets supported. The target DataModels specifies multiple supported platforms (watchos, ios).

macOS version

14.1.2

Tuist version

3.4.0

Xcode version

15.2

[pepicrft]

Thanks a lot for reporting this @thebarndog. The issue is that we haven't yet updated the build, test and run CLI commands to support multi-platform targets. I've created a PR to improve the presentation of the error message, and created an issue to add support for it.
Let's continue the discussion in the latter.

[pepicrft]

Note @thebarndog that if you use --platform when invoking tuist build, you won't hit the issue.