At present:

dotnet publish -c Release path/code -o path/app /p:PublishSingleFile=true

throws error:

error NETSDK1031: It is not supported to build or publish a self-contained application without specifying a RuntimeIdentifier. Please either specify a RuntimeIdentifier or set SelfContained to false.

which requires a fix like:

dotnet publish -c Release path/code -o path/app /p:PublishSingleFile=true -r osx-x64

It is fairly a common usecase to publish an app for platform with same RID as host.

However, the error is good to keep it an explicit and conscious decision of user; instead of falling back to some default value.

Please add --use-current-rid or --infer-rid option for automation and documentation convenience.

This way user will still explicitly specify RID option, without supplying platform specific value.