Using yield_fixture as function causes fixtures to run twice

[Wilfred]

import pytest

def inner_function():
    print "begin inner_function!"
    yield
    print "end inner_function!"

my_fixture = pytest.yield_fixture(scope='session', autouse=True)(inner_function)

def test_foo():
    assert True

Running pytest -s foo.py gives:

foo.py begin inner_function!
begin inner_function!
.end inner_function!
end inner_function!
========= 1 passed in 0.01 seconds ============

It seems that py.test is erroneously thinking that inner_function is a fixture. Sometimes (because I want to use my function in other contexts too) I want to use yield_fixture as a function and pass my target function directly. When this happens, py.test tries to run my fixture twice.

[nicoddemus]

From #1480 it seems you are using pytest 2.6... could you try upgrading and see if you still have this problem?

[RonnyPfannschmidt]

the fixture decorator does indeed modify the function in-place by adding a new attribute

[Wilfred]

I can reproduce this on pytest 2.9.1 too.

[RonnyPfannschmidt]

the current implementation cannot support usage as non-decorator, since it modifies the function on passtrough

[nicoddemus]

Should we close this?

[RonnyPfannschmidt]

No, its still "broken" as far as I can tell

[nicoddemus]

I understand, I was asking more in the sense of "closing as not supported"

[RonnyPfannschmidt]

well, we should issue a pytest warning in case more than one active fixture has the same identity

[nicoddemus]

This is fixed by #2849

[RonnyPfannschmidt]

@nicoddemus nope, #2849 fixes double use of the decorator

this is about naming the decorator result and the original function differently
in that case pytest find 2 fixtures with the same identity but different name in the globals

[nicoddemus]

@RonnyPfannschmidt OK, thanks for the clarification

[nicoddemus]

This has been fixed, inner_function is called only once now:

test-foo.py begin inner_function!
.end inner_function!
                                                                                [100%]

==================================== 1 passed in 0.04 seconds =====================================