[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Dima Tisnek]

Dima Tisnek  added the comment:

Thank you for explanation, Jason!

I guess that the bug report and the patch were too technical for me to 
understand 

I'm happy with the behaviour in Python 3.8.1 and now I know it's going to stay, 
I'll just change the tests in our code base.

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Jason Fried]

Jason Fried  added the comment:

Its not possible to have it both ways.  Also it stinks too much of trying to 
guess. 

The root of your issue is you want a normal MagicMock not an AsyncMock. Its the 
automatic behavior of patch to pick AsyncMock vs MagicMock that is the heart of 
your issue.  This bug fix doesn't involve that behavior at all, and AsyncMock 
was measurably broken without the fix, in an unavoidable way.  Your breakage is 
avoidable by changes to how you patch.  

 with patch("bar", return_value=42)

To still do it the old way you would have to pass new_callable=MagicMock to 
patch.

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Karthikeyan Singaravelan]

Change by Karthikeyan Singaravelan :


--
nosy: +xtreak

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Dima Tisnek]

Dima Tisnek  added the comment:

I think this deserves discussion :)

On one hand, it's a welcome change, on another it's kind of a regression.

Up until 3.8, our tests used to look like this:

---
# code under test

async def foo():
return await bar()


# test

async def helper(value):
return value


async def test_foo():
with patch("bar", return_value=helper(42)):
assert await foo() == 42
---

I feel that the default class `patch()` uses for `new` has crept in too quietly 
in 3.8.

At the same time, `helper` was only used because there was no `AsyncMock`.
(or at times, a 3rd party library, `asynctest` was used).



So, on one hand, it's a bit of a regression, but on the other, looking ahead, I 
would really like `unittest.mock` to do the right thing.



Can we have it both ways? If not, what way is a better way?

--
nosy: +Dima.Tisnek

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Lisa Roach]

Change by Lisa Roach :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Andrew Svetlov]

Andrew Svetlov  added the comment:


New changeset b2744c1be73f5af0d2dc4b952389efc90c8de94e by Andrew Svetlov (Lisa 
Roach) in branch '3.8':
[3.8] bpo-38857: AsyncMock fix for awaitable values and StopIteration fix [3.8] 
(GH-17269) (#17304)
https://github.com/python/cpython/commit/b2744c1be73f5af0d2dc4b952389efc90c8de94e


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nosy: +asvetlov

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Lisa Roach]

Change by Lisa Roach :


--
pull_requests: +16796
pull_request: https://github.com/python/cpython/pull/17304

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Lisa Roach]

Lisa Roach  added the comment:


New changeset 046442d02bcc6e848e71e93e47f6cde9e279e993 by Lisa Roach (Jason 
Fried) in branch 'master':
bpo-38857: AsyncMock fix for awaitable values and StopIteration fix [3.8] 
(GH-17269)
https://github.com/python/cpython/commit/046442d02bcc6e848e71e93e47f6cde9e279e993


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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Jason Fried]

Change by Jason Fried :


--
keywords: +patch
pull_requests: +16761
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/17269

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Jason Fried]

Change by Jason Fried :


--
type:  -> behavior

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[issue38857] AsyncMock issue with awaitable return_value/side_effect/wraps

[Jason Fried]

New submission from Jason Fried :

If you are trying to use AsyncMock to mock a coroutine that returns awaitable 
objects, AsyncMock awaits on those objects instead of returning them as is. 

Example:
  mock = AsyncMock(return_value=asyncio.Future())
  v = await mock()  # blocks on trying to await the future

Expected:
  mock = AsyncMock(return_value=asyncio.Future())
  v = await mock()
  assert isisnstance(v, asyncio.Future)

This problem affects side_effects and wraps.

--
components: Library (Lib)
messages: 357000
nosy: fried, lisroach
priority: normal
severity: normal
status: open
title: AsyncMock issue with awaitable return_value/side_effect/wraps
versions: Python 3.8, Python 3.9

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