False positive expression-not-assigned when calling functions with no return inside ternary expression

[da-dada]

Bug description

def f1():
    pass


def f2():
    pass


test = True
f1() if test else f2()

Configuration

No response

Command used

pylint test.py

Pylint output

test.py:9: [W0106(expression-not-assigned), ] Expression "f1() if test else f2()" is assigned to nothing

Expected behavior

no warning (according to documentation of pylint)

Pylint version

2.16.0.b1

OS / Environment

windows

[mbyrnepr2]

If it is re-written as the following, the message goes away; so I think it makes sense for consistency to consider the one-line version a false positive:

if test:
    f1()
else:
    f2()

[mbyrnepr2]

Looking into the origins of the conditional expression and it looks like y if x else z was introduced as a replacement to this syntax:
x and y or z.

I don't see anything specifically stating that it must be assigned to a name; although the real-world code examples in the link mostly are assigning to a name.

PEP308
Motivating use case (from PEP308)
real-world code fragments (from PEP308)

[nickdrozd]

There are at least four ways to deal with this warning.

1. Convert the conditional expression to an if / else block:

# if / else blocks
if test:
    f1()
else:
    f2()

2. Explicitly discard the value of the conditional expression:

_ = f1() if test else f2()

3. Use a conditional expression to determine the function, then call the result:

(f1 if test else f2)()

4. Just disable the warning:

# pylint: disable = expression-not-assigned
f1() if test else f2()

If a one-liner is desired, I suggest going with option 3. But in any case I don't think any changes ought to be made to Pylint to accommodate the original. One coder's false positive is another's false negative.

[Pierre-Sassoulas]

1) is the code almost everyone use There's only one example of actual function in one line (print 'succeed' if pred(x) else 'failed', ':', x) in the link provided by @mbyrnepr2. and it's the recommended snippet since python 3.0 (I recommend that people leave existing and/or code alone but start writing if/else expressions in new code only.). But nonetheless it's still valid python code and if the function always return None then 2) and 3) is just dancing around to appease the linter. Discouraging it should be another message like function-call-without-assignement-in-ternary and seeing how it's very seldom seen, probably not worth it (imo).