Is there a way to go from a subsystem's class to an instantiated instance? example, given

class Black(PythonToolBase):

, if I have

Black

, can I get an instance

black

with all of the options filled in? I'm hoping to invoke

black.pex_requirements()

, but that's an instance method

Like, without running through the async rule graph?

async def _run_black(
    request: AbstractFmtRequest.Batch,
    black: Black,
    interpreter_constraints: InterpreterConstraints,
) -> FmtResult:
    black_pex_get = Get(
        VenvPex,
        PexRequest,
        black.to_pex_request(interpreter_constraints=interpreter_constraints),

the problem I have is that I have

@union
class ExportableTool:
    resolve_name: ClassVar[str]
    subsystem_cls: ClassVar[type]

class BlackExportableTool(ExportableTool):
    resolve_name = Black.options_scope
    subsystem_cls = Black

and in a rule I've got an instance of

BlackExportableTool

and would like to somehow get an instance of

black

You can reques it with a `Get`:

Get(Black, {})

but I guess the type is not known statically, no worries, you can leverage https://github.com/pantsbuild/pants/pull/16929 to provide the type dynamically.

I finally had a chance to try this out. I don't think that works because I'd need to parametrise the output type, but that MR only allows the input type...