Change return type to `Stream<? extends TestTemplateInvocationContext>`

[sormuras]

https://github.com/junit-team/junit5/blob/f5b78f68c6a90dfa63611c7a10027581c5d913ba/junit-jupiter-api/src/main/java/org/junit/jupiter/api/extension/TestTemplateInvocationContextProvider.java#L87

Michael wrote:

I mean I tried to do Stream.generate(() -> new MyInvocationContext()).limit(/*number*/)
This does not work.
but Stream.generate(() -> new MyInvocationContext()).limit(/*number*/).map(e -> e) works...

[sormuras]

Question is, can we change the return type without breaking existing code?

[marcphilipp]

According to https://wiki.eclipse.org/Evolving_Java-based_APIs_2#Evolving_API_interfaces_-_API_methods that would break binary compatibility. We should have declared the method like that initially, though.

[kaipe]

On a related topic ...
Wouldn't it be better to have return type Iterable?
I figure it's a simplier abstraction that is easy to implement and still provides all capabilities that are requied by JUnit.

[marcphilipp]

I don't think it makes a big difference. Stream nowadays has many factory methods that allow Iterator-like implementations. Moreover, we ensure Stream.close is also called to support external resources such as files.