Description
Information
When writing a reproduction for #1381 I stumbled upon this.
- rustworkx version: currently on main (commit
f2f45425c70b49d89aa5527271a34f64fb114f1d) - Python version: 3.12
- Rust version: ...
- Operating system: ubuntu
What is the current behavior?
The method PyDiGraph.extend_from_edge_list restricts the input graph's to PyDiGraph[_S | None, _T | None]. In turn this causes static type checker to rightfully complain when the typevars are declared to but not None.
This is because PyDiGraph is defined to be invariant WRT the _T and _S typevars. This implies that PyDiGraph[int, int] is not assignable to PyDiGraph[int | None, int | None].
I tried searching for more function with | None and found that the methods (of both graph classes) extend_from_edge_list, extend_from_weighted_edge_list, add_edges_from_no_data, and the functions digraph_complement, graph_complement, complement, local_complement.
Probably suffer from a similar issue.
What is the expected behavior?
I expected to be able to run the reproduction below without mypy / pyright complaining about bad argument.
As annotation fixes:
- for the methods
extend_from_edge_list,extend_from_weighted_edge_list,add_edges_from_no_data, this is simply removing the| None. - For the universal
complementand it two non-universal variant functions, if I understand the documentation correctly, the return type should have justNoneon the edge payload typvar, and not_T | None. - For
local_complement, I think the type annotation is correct as is.
The annotations make me think that the graph classes are not intended to behave invariantly, but rather covariantly, if this is desirable the way to do it is:
# in rustworks.pyi
_S_co = TypeVar("_S_co", default=Any, covariant=True)
_T_co = TypeVar("_T_co", default=Any, covariant=True)
class PyGraph(Generic[_S_co, _T_co]):
...
class PyDiGraph(Generic[_S_co, _T_co]):
...Personally, I think its better to keep them invariant, and if users of rustworkx want covariance / contravariance in their external functions they can define their signature as they like.
Steps to reproduce the problem
# t.py
import rustworkx as rx
graph = rx.PyDiGraph[int, int]()
graph.extend_from_edge_list([(0, 1), (2, 1), (3, 1), (1, 4)])When run mypy t.py I get
t.py:5: error: Invalid self argument "PyDiGraph[int, int]" to attribute function "extend_from_edge_list" with type "Callable[[PyDiGraph[_S | None, _T | None], Iterable[tuple[int, int]]], None]" [misc]
Found 1 error in 1 file (checked 1 source file)
and pyright t.py (in "basic" setting):
/home/barak-katzir/dev/rustworkx-check/t.py
/home/barak-katzir/dev/rustworkx-check/t.py:6:7 - error: Cannot access attribute "extend_from_edge_list" for class "PyDiGraph[int, int]"
Could not bind method "extend_from_edge_list" because "PyDiGraph[int, int]" is not assignable to parameter "self"
"PyDiGraph[int, int]" is not assignable to "PyDiGraph[int | None, int | None]"
Type parameter "_S@PyDiGraph" is invariant, but "int" is not the same as "int | None"
Type parameter "_T@PyDiGraph" is invariant, but "int" is not the same as "int | None" (reportAttributeAccessIssue)
1 error, 0 warnings, 0 informations