out-there theoretical question, but could Pants handle a Generic rule? example: instead of subclassing

ExportPythonToolSentinel

we could have

Tool = TypeVar("Tool", bound=ExportablePythonTool)  # ExportablePythonTool doesn't exist yet

class ExportPythonToolSentinel(Generic(Tool)):
    ...

@rule
def generic_export(_: ExportPythonToolSentinel[Tool], tool: Tool):
    ...

I'm not too familiar with the inner working of Python's type hint system and Pant's interaction with it. For example, I don't know if the references to

Tool

in the

generic_export

have to be the same. It seems kindof related to UnionRule?

@hundreds-father-404 ccing you so this doesn’t get lost in the scrollback

generally, rule signatures can't be complex like

List[str]

or

Optional[str]

. They have to a be a single

type()

. That's because the rule graph goes from types to types, and we store the information in Rust of the Python

type

Oh, that makes sense, thanks! I wonder if I can get something off the ground with python crimes overriding

__getitem__

to return unique types.

Experimentation is definitely welcome on how to make the Rules API more ergonomic!