False positive E1136 – unsubscriptable-object

[Paulchen5]

Bug description

This is fine:

end_of_good_plan = good_case_plan_structures.get("<key>", None)
end_of_bad_plan = bad_case_plan_structures.get("<key>", None)

if end_of_good_plan is not None and end_of_bad_plan is not None:
    end_of_good_plan[0]

This throws an error:

end_of_good_plan = (
    good_case_plan_structures["<key>"]
    if "<key>" in good_case_plan_structures
    else None
)
end_of_bad_plan = (
    bad_case_plan_structures["<key>"]
    if "<key>" in bad_case_plan_structures
    else None
    )

if end_of_good_plan is not None and end_of_bad_plan is not None:
    end_of_good_plan[0]

Useful type hints:
(variable) good_case_plan_structures: dict[str | None, list[SecretClass]]
(variable) bad_case_plan_structures: dict[str | None, list[SecretClass]]

Configuration

default configuration

Command used

`pylint --disable fixme . `

Pylint output

************* Module src.****.****
src/****/****.py:****:****: E1136: Value 'end_of_good_plan' is unsubscriptable (unsubscriptable-object)

Expected behavior

No error because it's type is being checked

Pylint version

pylint 3.3.7
astroid 3.3.10
Python 3.12.0 (main, Dec 23 2024, 00:59:44) [Clang 16.0.0 (clang-1600.0.26.4)]

OS / Environment

macOS 15.5, zsh terminal with oh-my-zsh and p10k theme

Additional dependencies

[zenlyj]

Thanks for reporting this, the issue lies in the inference of end_of_good_plan, it is being inferred as None value in the given example. It is also worth noting that no error is raised when the if condition is just a single None check:

good_case_plan_structures = {}
bad_case_plan_structures = {}

end_of_good_plan = (
    good_case_plan_structures["<key>"]
    if "<key>" in good_case_plan_structures
    else None
)
end_of_bad_plan = (
    bad_case_plan_structures["<key>"]
    if "<key>" in bad_case_plan_structures
    else None
    )

if end_of_good_plan is not None:
    end_of_good_plan[0]  # no error

if end_of_bad_plan is not None:
    end_of_bad_plan[0]  # no error

if end_of_good_plan is not None and end_of_bad_plan is not None:
    end_of_good_plan[0]  # error, false positive
    end_of_bad_plan[0]  # error, false positive