A logical place is

src/python/pants/backend

, which allows us to have a single source root, and use the obvious package prefix

pants.backend.

for v2 backends. However this ends up entangling the v1 and v2 backends at least in some cases (e.g., Python).

We could create a new source root

backends/src/python/pants/backend

, which is maybe a bit clunky.

Or we could come up with a new synonym for backend.

component

?

Renaming the existing

pants.backend

to

pants.backendv1

is possible, but requires deprecation and stuff. And seems like a hassle.

Or we could call these

pants.backend2

or something

Anyway, let the bikeshedding begin...

We can allow v1 backends to depend on v2 backends

See discussion in doc