option_adt_lib_example.py

from typing import Dict, Generic, TypeVar

import pytest
from adt import Case, adt

T = TypeVar("T")


@adt
class Option(Generic[T]):
    SOME: Case[T]
    NONE: Case


def parse_name(request: Dict[str, str]) -> Option[str]:
    name = request.get("name")
    return Option.SOME(name) if name else Option.NONE()


@pytest.mark.parametrize(
    "key,value,expected_result",
    [
        ("name", "john", "john"),
        ("not-a-name", "jaqen h'ghar", "No value"),
    ],
)
def test_parse(key, value, expected_result):
    parsed_name = parse_name({key: value})
    actual_value = parsed_name.match(some=lambda v: v, none=lambda: "No value")
    assert actual_value == expected_result