(fixtures): Replace fixture represenation with a class #12473

Glyphack · 2024-06-18T10:27:53Z

During the sprint we discussed fixing the above issue and thought maybe it's a better idea to add a better represenation to fixtures. To do this without patching the object more, this PR refactors fixtures to have a class with attributes.
The main rational behind that is:

Now we have a type for fixtures makes it easier to check for fixture types and no need to perform cast on objects. Removed monkey patching.
They are no longer functions that carry a class within them.
When you decorate a function with a fixture it's not possible to call it anymore. So it makes more sense for it to not be a function or method.

Example

Previously we had:

===================================== short test summary info ======================================
FAILED tmp31nzhe4b.py::test_something - assert fixt == 42
======================================== 1 failed in 0.03s =========================================

where fixt is a pytest fixture function that is not replaced by it's value(directly used)

Now we print:

===================================== short test summary info ======================================
FAILED tmp31nzhe4b.py::test_something - assert pytest_fixture(<function fixt at *>) == 42 
======================================== 1 failed in 0.03s =========================================

testing/code/test_source.py

testing/test_compat.py

Glyphack · 2024-07-04T18:48:51Z

Hey @The-Compiler @RonnyPfannschmidt I rebased the PR could you please take a look?

changelog/11525.improvement.rst

src/_pytest/compat.py

src/_pytest/fixtures.py

webknjaz · 2024-07-04T19:58:01Z

testing/code/test_source.py

@@ -478,12 +478,13 @@ def deco_mark():
    def deco_fixture():
        assert False

-    src = inspect.getsource(deco_fixture)
+    # Since deco_fixture is now an instance of FixtureFunctionDef the getsource function will not work on it.
+    with pytest.raises(Exception):


Could you assert against a more specific exception? As I understand, this is not testing that something went wrong but it's not clear what exactly. Also, it's usually a good idea to use the match= regex with this helper.

Yes will apply. This tries to document the behavior more than testing anything. Before introducing the FixtureFunctionDefinition it was possible to run inspect.getsource on fixtures but now it's not. This is just describing the behavior. I'm open to removing it as well.

I changed it to a more specific error. Do you think we can remove the test? This just tests that you cannot use inspect on fixture functions.

I think we can remove this test. I removed it.

webknjaz · 2024-10-23T11:18:37Z

Hey @Glyphack, could you resolve the merge conflicts / rebase this?

Glyphack · 2024-10-23T13:51:42Z

Hey @Glyphack, could you resolve the merge conflicts / rebase this?

Yes will do today.

RonnyPfannschmidt

Iove where this is going

It opens up nice follow ups

src/_pytest/compat.py

RonnyPfannschmidt · 2024-10-25T10:08:26Z

src/_pytest/compat.py

 def get_real_func(obj):
    """Get the real function object of the (possibly) wrapped object by
-    functools.wraps or functools.partial."""
+    :func:`functools.wraps`, or :func:`functools.partial`, or :func:`pytest.fixture`."""
+    from _pytest.fixtures import FixtureFunctionDefinition


I believe we can drop fixture definition from that , we should pass the definitions attribute

Are you suggesting to pass the FixtureFunctionDefinition object to this function? If I understand correctly this function is expected to take any object and return the real object according to this test testing the behavior:
https://github.com/Glyphack/pytest/blob/3d7416c2dd5dcf2d60a8b30636dcc90978c64215/testing/test_compat.py#L63

As fixture definitions are no longer wrapping functions into other functions

The suggestion is to no longer consider them wrappers and passing the function directly

@RonnyPfannschmidt Sorry I didn't fully understand your comment.

The current unwrapping behavior here is only for two cases:

The pytest fixture is applied on a function so I can display this case with Fixture(f)

The pytest fixture is decorated so we have deco(Fixture(f))

The first case is handled by obj = obj._get_wrapped_function() line and second case is handled by obj = inspect.unwrap(obj, stop=lambda x: type(x) is FixtureFunctionDefinition).

If we drop any of them we cannot handle one of those two cases.

But I feel I am missing your point but unwrapping to me are these two lines.

Decorators cannot apply to a fixture definition

So that should trigger a error

It's wrong even now

I was wrong about that but the behavior is still needed. For example this test fails if we don't do unwrapping in this function:
https://github.com/Glyphack/pytest/blob/a6318c944f907bc350922c3961365e9ecd8d3e81/testing/python/integration.py#L11

The reason is that getfslineno is using this function to unwrap a decorator:
https://github.com/Glyphack/pytest/blob/a6318c944f907bc350922c3961365e9ecd8d3e81/src/_pytest/_code/code.py#L1341

I think the solution is to make a separate function for the cases when we want to perform the unwrapping? What is your suggestion?

What I meant is that we no longer ought to pass fixture definition to anything that unwrapped

Definition is no longer a function

Perhaps we should drop the call altogether

Thanks I realized the reason my code required this check to be here was that I was getting objects using the fixture name instead of their actual name and mistakenly I calling this on non fixture objects. After fixing that I could remove the get_real_method and simplify this function.

src/_pytest/fixtures.py

Glyphack · 2024-10-27T11:17:13Z

Thank you both for the review. I left some TODO comments I will address them in a follow up PR.

Co-authored-by: Bruno Oliveira <[email protected]>

Co-authored-by: Ran Benita <[email protected]>

…-callable

Glyphack · 2024-12-05T18:29:31Z

Thank you so much for the reviews. Please take another look and let me know if there are more improvements. I was busy last week I will be quicker in resolving them this time.
@nicoddemus I like to help with the PR you created. I'll take a look there once this is done.

bluetech

Thanks for the update! Please see my comments.

@nicoddemus I like to help with the PR you created. I'll take a look there once this is done.

I think @nicoddemus's intention is for you to incorporate his suggestions in this PR, this way we can review & merge everything together.

bluetech · 2024-12-05T22:50:15Z

src/_pytest/fixtures.py

-        "https://docs.pytest.org/en/stable/deprecations.html#calling-fixtures-directly about how to update your code."
-    )
-
-    @functools.wraps(function)


I think the best thing would be to use functools.update_wrapper in FixtureFunctionDefinition.__init__, unless there is something preventing it.

bluetech · 2024-12-05T22:52:45Z

src/_pytest/fixtures.py

@@ -1352,7 +1360,7 @@ def fixture(
 def yield_fixture(
    fixture_function=None,
    *args,
-    scope="function",
+    scope: _ScopeName = "function",


This comment is still relevant

bluetech · 2024-12-05T22:56:39Z

src/_pytest/fixtures.py

+        self.__name__ = self.name
+        self._fixture_function_marker = fixture_function_marker
+        self._fixture_function = function
+        self._instance = instance


I wonder if it wouldn't be simpler to keep self._fixture_function bound to instance instead of keeping _instance and binding it lazily? Is there a reason why it needs to be lazy?

I applied this and it's simpler. I don't think there's any reason to do it when we get the fixture.

bluetech · 2024-12-05T22:57:35Z

src/_pytest/fixtures.py

@@ -1271,7 +1279,7 @@ def fixture(
    autouse: bool = ...,
    ids: Sequence[object | None] | Callable[[Any], object | None] | None = ...,
    name: str | None = None,
-) -> FixtureFunctionMarker: ...
+) -> FixtureFunctionDefinition: ...


This comment is still relevant

nicoddemus · 2024-12-06T13:34:41Z

I think @nicoddemus's intention is for you to incorporate his suggestions in this PR, this way we can review & merge everything together.

@bluetech not really, I meant to apply those later (I only created a Draft PR to not lose the local commits I made).

bluetech · 2024-12-06T19:50:19Z

@bluetech not really, I meant to apply those later (I only created a Draft PR to not lose the local commits I made).

Ah sorry for the assumption. The reason I thought it would be better to combine is that merging as-is would introduce a typing regression (fixture functions would lose their signature). But it's only temporary so not a problem.

bluetech

Looks good to me!

nicoddemus

Thanks @Glyphack!

* Carry around parameters and return value in `FixtureFunctionDefinition`. * Add `FixtureParams` to `FixtureDef`. Follow up to pytest-dev#12473.

youtux · 2025-01-11T23:11:55Z

FYI, this breaks pytest-factoryboy, but that's something I have to deal with.
Just wanted to let you know, in case maybe other users could have the same issue.

That being said, __pytest_wrapped__ was an internal API, so 100% agree that there is no guaranteed behavior on these.

Glyphack commented Jun 20, 2024

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Glyphack changed the title ~~(assertion): Use repr for pytest fixtures and set repr for pytest fixtures~~ (fixtures): Replace fixture represenation with a class Jun 20, 2024

psf-chronographer bot added the bot:chronographer:provided (automation) changelog entry is part of PR label Jun 20, 2024

Glyphack force-pushed the reprs-assert-callable branch 3 times, most recently from bf90fca to d25a8d9 Compare June 20, 2024 13:51

Glyphack commented Jun 20, 2024

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Glyphack marked this pull request as ready for review June 20, 2024 15:19

Glyphack force-pushed the reprs-assert-callable branch 2 times, most recently from 3d2ec33 to 84cc5b7 Compare July 4, 2024 18:48

webknjaz reviewed Jul 4, 2024

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Glyphack force-pushed the reprs-assert-callable branch 3 times, most recently from f0324a5 to 9d2a916 Compare July 30, 2024 18:37

RonnyPfannschmidt mentioned this pull request Aug 19, 2024

Pytest integration reagento/dishka#124

Open

Glyphack force-pushed the reprs-assert-callable branch from 641a3a1 to bc0a0e5 Compare October 23, 2024 14:30

Glyphack requested review from webknjaz and RonnyPfannschmidt October 23, 2024 19:37

RonnyPfannschmidt approved these changes Oct 25, 2024

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RonnyPfannschmidt added this to the 8.4 milestone Nov 12, 2024

Glyphack added 6 commits November 23, 2024 16:20

feat: use repr for pytest fixtures

41c7c2c

(fixture) create a new class to represent fixtures

cee9044

fix: update code to use new fixture definitions

004f29f

Update AUTHORS

224595a

chore: add changelog entry

8666dfb

add test case for asserting missing fixture

b724030

Glyphack and others added 10 commits December 5, 2024 18:17

Update changelog/11525.improvement.rst

fb4ce59

Co-authored-by: Bruno Oliveira <[email protected]>

Update src/_pytest/fixtures.py

3f22fe5

Co-authored-by: Bruno Oliveira <[email protected]>

Update src/_pytest/fixtures.py

98ea2f5

Co-authored-by: Bruno Oliveira <[email protected]>

Update src/_pytest/fixtures.py

72269d8

Co-authored-by: Ran Benita <[email protected]>

Pass args by name to FixtureFunctionDefinition

d625874

Add comments for __name__ and __get__

2f1a17e

Check non-internal use of FixtureFunctionDefinition

d909768

Use pytester

56899f6

Update test description

ad3f0fa

Merge branch 'main' of github.com:pytest-dev/pytest into reprs-assert…

845d50e

…-callable

bluetech requested changes Dec 5, 2024

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Glyphack added 6 commits December 6, 2024 16:10

Revert changing fixture annotation

a6d0998

Revert yield_fixture annotation

0bb4f14

use functool.wraps when applying fixture

68a66b5

Remove __wrapped__ attribute from FixtureFunctionDefinition

a160a6a

Bind fixture_function when there is an instance

b1de16a

Remove unused attribute

3ba7108

Glyphack added 2 commits December 7, 2024 10:28

get_real_func will unwrap the underlying fixture function

475deb1

Merge branch 'main' into reprs-assert-callable

723a8f3

bluetech approved these changes Dec 7, 2024

View reviewed changes

nicoddemus approved these changes Dec 7, 2024

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nicoddemus merged commit ecde993 into pytest-dev:main Dec 7, 2024
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nicoddemus mentioned this pull request Dec 7, 2024

typing: Improve FixtureDefinition and FixtureDef #13036

Open

youtux mentioned this pull request Jan 11, 2025

Fix compatibility with pytest >= 8.4 pytest-dev/pytest-factoryboy#232

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