Spy async bug introduced in Python 3.8.1

[adamcharnock]

I believe bpo-38875 has introduced a bug in mocker.spy(). Spied coroutines are no longer awaited as they should be.

This test highlights the issue:

import pytest


class MyClass:
    async def method(self):
        return "hi"


@pytest.mark.asyncio
async def test_spy_async(mocker):
    my_obj = MyClass()
    mocker.spy(my_obj, 'method')

    returned = await my_obj.method()

    # Passes
    assert my_obj.method.called

    # AssertionError: assert <coroutine object MyClass.method at 0x10f2a5d40> == 'hi'
    assert returned == "hi"

It looks like spy() (specifically, wrapper() defined within spy()) returns a coroutine and expects unittest's patch() do to the awaiting, rather than doing the awaiting itself. This worked until bpo-38875 changed this behaviour. Now unittest will no longer await retuned awaitables, rather it returns them.

[adamcharnock]

If anyone needs a quick workaround, I'm using something like this:

    if sys.version_info >= (3, 8):
        from unittest.mock import AsyncMock
        redis_pool.grow = AsyncMock(wraps=redis_pool.grow)
    else:
        mocker.spy(redis_pool, "grow")

    assert redis_pool.grow.call_count == 123

AsyncMock is new in 3.8

[nicoddemus]

Hi @adamcharnock,

Thanks for the report and workaround.

Would you consider opening up a PR with this change?

[k4nar]

Thank you very much for this fix! Do you know when it will be released? 🙏

[nicoddemus]

Thanks for the ping @k4nar! Just released 3.0.0 with this fix. 👍

[k4nar]

Awesome, thank you for the responsiveness! Stay safe :) .