Stuck on an issue?

Lightrun Answers was designed to reduce the constant googling that comes with debugging 3rd party libraries. It collects links to all the places you might be looking at while hunting down a tough bug.

And, if you’re still stuck at the end, we’re happy to hop on a call to see how we can help out.

Short-circuit does not work for me in pipe()

See original GitHub issue

Issue Description

Describe the bug Short-circuit does not work for me in pipe(). Maybe i’m using this function in a wrong way. If so, please tell me how it should be.

Thank you.

To Reproduce Execute this code with Expression 2.0.0:

from expression import pipe, effect, Ok
from expression.core.option import Nothing


@effect.result[int, Exception]()
def mulby10(x):
    yield from Ok(x * 10)
 
@effect.option[int]()
def divbyzero(x):
    try:
        yield from Ok(x / 0)
    except Exception as exn:
        yield from Nothing

def main():
    v = 1
    res = pipe(
        v,
        divbyzero,
        mulby10
        )
    print(f"{res=}")

if __name__ == "__main__":
    main()

It executes mulby10 after divbyzero returns Nothing and shows error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/Users/davaeron/repos/automation/automation/cli.py", line 18, in main
    res = pipe(
  File "/Users/davaeron/repos/automation/__pypackages__/3.10/lib/expression/core/pipe.py", line 136, in pipe
    return compose(*fns)(value)
  File "/Users/davaeron/repos/automation/__pypackages__/3.10/lib/expression/core/compose.py", line 136, in _compose
    return reduce(lambda acc, f: f(acc), fns, source)
  File "/Users/davaeron/repos/automation/__pypackages__/3.10/lib/expression/core/compose.py", line 136, in <lambda>
    return reduce(lambda acc, f: f(acc), fns, source)
  File "/Users/davaeron/repos/automation/__pypackages__/3.10/lib/expression/core/builder.py", line 96, in wrapper
    result = self._send(gen, done)
  File "/Users/davaeron/repos/automation/__pypackages__/3.10/lib/expression/core/builder.py", line 52, in _send
    yielded = gen.send(value)
  File "/Users/davaeron/repos/automation/automation/cli.py", line 7, in mulby10
    yield from Ok(x * 10)
TypeError: unsupported operand type(s) for *: 'Nothing_' and 'int'

Expected behavior res=Nothing after divbyzero function, mulby10 should be unexecuted

Additional context

OS MacOS 12.4
Expression version: 2.0.0
Python version: 3.10.4

Issue Analytics

State:
Created 8 months ago
Comments:5

Top GitHub Comments

1reaction

dbrattlicommented, Jul 8, 2022

from expression import pipe, effect, Ok, Nothing, option


@effect.option[int]()
def mulby10(x: int):
    yield x * 10


@effect.option[int]()
def divbyzero(x: int):
    try:
        yield (x // 0)
    except Exception:
        yield from Nothing


def main():
    v = 1
    res = pipe(
        v,
        divbyzero,
        option.bind(mulby10),
    )
    print(f"{res=}")


if __name__ == "__main__":
    main()

0reactions

pertsevdscommented, Jul 9, 2022

from functools import reduce
from typing import Any
from expression import effect, Error, Ok


class DivisionByZeroError(Error):
    def __init__(self, error="Division by zero"):
        super().__init__(error)
    def bind(self, mapper):
        return self

class OtherError(Error):
    def __init__(self, error="Other error"):
        super().__init__(error)
    def bind(self, mapper):
        return self


@effect.result[int, Exception]()
def mulby10(x: int):
    try:
        yield (x * 10)
    except Exception:
        yield from OtherError()

@effect.result[int, Exception]()
def divbyzero(x: int):
    try:
        yield (x // 0)
    except Exception:
        yield from DivisionByZeroError()


def bound_compose(*fns):
    def _compose(source: Any) -> Any:
        match source:
            case Ok():
                return reduce(lambda acc, f: acc.bind(f), fns, source)
            case Exception():
                return source
            case _:
                return reduce(lambda acc, f: acc.bind(f), fns, Ok(source))
    return _compose

def bound_pipe(__value: Any, *fns) -> Any:
    return bound_compose(*fns)(__value)

def main():
    v = 1
    res = bound_pipe(
        v,
        divbyzero,
        mulby10
    )
    match res:
        case Ok(value):
            print(f"{value=}")
        case DivisionByZeroError(e) | OtherError(e):
            print(e)
        case _:
            print("Not implemented.")


if __name__ == "__main__":
    main()

Something like this? Does this looks reasonable?