The ellipsis in the function parameters of challenge intermediate/literalstring causes challenge failed

[b1indsight]

In challenge intermediate/literalstring, function execute_query has a parament accepted Iterable[str]，and set default value .... The same pattern is observed in the provided solution.

def execute_query(sql, parameters: Iterable[str] = ...):
    """No need to implement it"""

This will cause a type check error by pyright

error: Expression of type "ellipsis" cannot be assigned to parameter of type "Iterable[str]"

It seems like I must access type check by changing Iterable[str] to Iterable[str] | EllipsisType , like

from typing import Iterable, LiteralString
from types import EllipsisType


def execute_query(sql: LiteralString, parameters: Iterable[str] | EllipsisType = ...):
    """No need to implement it"""

or change ... to () for type check.

from typing import Iterable, LiteralString
from types import EllipsisType


def execute_query(sql: LiteralString, parameters: Iterable[str] = ()):
    """No need to implement it"""

I don't think either of the above solutions to be the best way for this issue, but I don't know any better way to use ellipsis for default parameter with type hint.

[laike9m]

May I ask which type checker are you using? Python-Type-Challenges uses pyright and it works as expected, see playground. It is normal that different type checkers behave differently here and there.

parameters: Iterable[str] = () works too, if you make a PR I'll accept it.

[b1indsight]

I'm using Pyright version 1.1.344, which you can reproduce in this playground.

I found a related discussion in this issue of pyright and the corresponding release note of version 1.1.329. The key change mentioned is:

Behavior Change: Added check for the use of an ellipsis for a default argument value for a function that is not in a stub, not overloaded, and without a placeholder implementation.

---

When an ellipsis is used in a function body, means not been implemented, Pyright treats the ellipsis as Any, for example:

from typing import LiteralString, Iterable
def execute_query(sql: LiteralString, parameters: Iterable[str] = ...):
     ...

will get:

> pyright --pythonversion=3.12  test.py
0 errors, 0 warnings, 0 informations 

When using docstring, pass, and NotImplementedError, Pyright will check the type of ellipsis used as a default parameter. This behavior causes the type check error.

from typing import LiteralString, Iterable
def execute_query(sql: LiteralString, parameters: Iterable[str] = ...):
    """Not implemented yet."""

>  pyright --pythonversion=3.12  test.py
test.py:3:67 - error: Expression of type "ellipsis" cannot be assigned to parameter of type "Iterable[str]"
    "ellipsis" is incompatible with protocol "Iterable[str]"
      "__iter__" is not present (reportGeneralTypeIssues)
1 error, 0 warnings, 0 informations 

---

I think adding an ellipsis within the function execute_query's body of question file is a better way to fix this. The solution file can pass the type check (I made a mistake for this).

[laike9m]

Thanks for digging into this. You're right about the current behavior (this comment describes it).

I'll make a change to question.py to use ellipsis in function body.