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Sarj Sarj Sarj Standards

prefer-non-nullable-collection

Avoid nullable list parameters that are immediately collapsed to an empty list.

SARJ082 Rule source Tests Catalog JSON

Why

When an implementation immediately replaces both None and an empty list with the same fresh empty list, the callable contract exposes an extra input state that its body does not retain.

Fix

After reviewing callers and list identity or mutation behavior, either require the list or accept Sequence[T] = () and materialize a list internally. Removing explicit None acceptance is an API migration.

Examples

Before — flagged Nullable list is immediately collapsed to an empty list
app/resolver.py
def resolve(candidates: list[str] | None = None) -> list[str]:
    return candidates or []
After — preferred Immutable empty default keeps omission non-nullable
app/resolver.py
from collections.abc import Sequence




def resolve(candidates: Sequence[str] = ()) -> list[str]:
    return list(candidates)