Disable assertion rewriting external modules #13421

Tusenka · 2025-05-13T03:15:58Z

Disable assertion rewriting of external modules. Closes 13403.

Tusenka · 2025-05-13T03:45:26Z

Need to squash commits - OK to close, I'll reopen a new one with one commit

RonnyPfannschmidt

thank you for getting this started

i believe we need to put the path handling into assertion state so it can correctly pass from the configuration and include the invocation dir/rootdir in a more safe manner than the current heusterics

testing/test_assertrewrite.py

src/_pytest/assertion/rewrite.py

testing/test_assertrewrite.py

src/_pytest/assertion/__init__.py

nicoddemus · 2025-05-16T11:29:55Z

I skimmed through the issue (I'm short on time so I cannot do a more through research), but looking at the code is not immediately clear to me so thought I would ask:

Note that we want to rewrite asserts for files belonging to a pytest plugin, even if they are not test_*.py files. How does this patch relate to that? This is an important behavior that should be kept.

Tusenka · 2025-05-16T16:18:51Z

I skimmed through the issue (I'm short on time so I cannot do a more through research), but looking at the code is not immediately clear to me so thought I would ask:

Note that we want to rewrite asserts for files belonging to a pytest plugin, even if they are not test_*.py files. How does this patch relate to that? This is an important behavior that should be kept.

At present time the fix is applied only for path which applies test_*py. The plugins are processed separately. I'll add some tests against that important part.

Tusenka · 2025-05-18T04:02:24Z

I skimmed through the issue (I'm short on time so I cannot do a more through research), but looking at the code is not immediately clear to me so thought I would ask:
Note that we want to rewrite asserts for files belonging to a pytest plugin, even if they are not test_*.py files. How does this patch relate to that? This is an important behavior that should be kept.

At present time the fix is applied only for path which applies test_*py. The plugins are processed separately. I'll add some tests against that important part.

Added some tests for plugin rewriting, it works now

Tusenka · 2025-05-19T04:15:53Z

testing/test_assertrewrite.py

+        with mock.patch.object(hook, "fnpats", ["*.py"]):
+            assert hook.find_spec("file") is None
+
+    def test_assert_rewrite_correct_for_conftfest(


mamy name it in another way - test_assert_rewrite_for_conftfest

RonnyPfannschmidt · 2025-05-24T06:52:28Z

src/_pytest/assertion/__init__.py

@@ -108,6 +109,19 @@ def __init__(self, config: Config, mode) -> None:
        self.trace = config.trace.root.get("assertion")
        self.hook: rewrite.AssertionRewritingHook | None = None

+    @property


this must mot use getwd instead use the invoction params

then we cannot change it on runtime as far as invocation param for pytester changes rootpath

sorry for the type - this code shoud use the rootdir or the invocationdir from the invocation params of the config
see https://docs.pytest.org/en/stable/reference/reference.html#pytest.Config.invocation_params as well as the config rootdir

My error, I mean as far as Invocation Param is frozen - it can't be changed on runtime. Pytester starts after the config has been loaded. So to change the rootpath for pytester I need to rewrite the rootpath in someway. I could mock all invocation params or I could use getcwd alongside with config rootdir for the testing purpose.

The complete object can be replaced with a changed one

ok. would be done)

But is config.invocation_params.dir the correct thing to use? If I execute the tests using pytest src/tests/foo.py, I expect pytest to continue to rewrite the same files as if I execute just pytest.

I feel we should use config.rootpath here? What do you think @RonnyPfannschmidt ?

indeed - the rootpath - else we miss imports to rewrite

nicoddemus

Thanks @Tusenka,

Left some comments, please take a look.

changelog/13403.bugfix.rst

nicoddemus · 2025-06-01T12:19:56Z

src/_pytest/assertion/__init__.py

        self.hook: rewrite.AssertionRewritingHook | None = None

+    @property
+    def rootpath(self):


We already have rootpath in Config, but this property returns something different so this is a bit misleading. I suggest we rename it to something else to avoid this confusion, how about:

Suggested change

def rootpath(self):

def invocation_path(self):

nicoddemus · 2025-06-01T12:21:59Z

src/_pytest/assertion/__init__.py

@@ -108,6 +109,19 @@ def __init__(self, config: Config, mode) -> None:
        self.trace = config.trace.root.get("assertion")
        self.hook: rewrite.AssertionRewritingHook | None = None

+    @property


But is config.invocation_params.dir the correct thing to use? If I execute the tests using pytest src/tests/foo.py, I expect pytest to continue to rewrite the same files as if I execute just pytest.

I feel we should use config.rootpath here? What do you think @RonnyPfannschmidt ?

src/_pytest/pytester.py

nicoddemus · 2025-06-01T12:26:37Z

testing/test_assertrewrite.py

+    @pytest.mark.skipif(
+        sys.platform.startswith("win32"), reason="cannot remove cwd on Windows"
+    )
+    @pytest.mark.skipif(
+        sys.platform.startswith("sunos5"), reason="cannot remove cwd on Solaris"
+    )


Are these skipif marks still necessary?

Is sunos still a supported python platform

As far as I'm aware sun is down

testing/test_assertrewrite.py

nicoddemus · 2025-06-01T12:39:59Z

testing/test_assertrewrite.py

+        self, pytester: Pytester, hook: AssertionRewritingHook, monkeypatch
+    ) -> None:
+        """If test files contained outside the rootpath, then skip them"""
+        pytester.makepyfile(


I would prefer to avoid mocking here, instead using a real scenario to ensure Python files outside of the rootpath do not have their assertions rewritten.

Please create a simple but real-world project using pytester, something like:

myproject/ /venv /lib /external_lib.py pyvenv.cfg /src main.py /tests conftest.py test_main.py pytest.ini outside.py

pytest.ini should have these contents:

[pytest] python_files = *.py

Then execute pytest.runpytest(), which will execute from the root of the above tree.

If I understand the objective of the issue correctly:

myproject/venv/lib/external_lib.py: should not have assertions rewritten -- the file is inside a virtual environment and is not part of a pytest plugin. The pyvenv.cfg file is how pytest detects virtual environments.

myproject/src/main.py: rewritten -- inside rootpath and matches python_files.

myproject/tests/conftest.py: rewritten -- conftest.py files are always rewritten.

myproject/tests/test_main.py: rewritten -- test files are always rewritten.

outside.py: should not have assertions rewritten -- outside the rootpath.

I think the scenario above should cover what needs to be tested.

We need to include an external plugin here too, to test the same scenario as in test_assert_rewrite_correct_for_plugins.

I've tried to create the structure along with a some conftest plugin. Even witout changes it doen't rewrite conftest plugins assertions

Example:
https://github.com/Tusenka/pytest/tree/disable_assertion_rewriting_external_modules_draft/testing/example_scripts/rewrite

However it sees only top-level plugins:
['anyio', '_hypothesis_ftz_detector', '_hypothesis_globals', '_hypothesis_pytestplugin', 'hypothesis', 'pytest_twisted', 'typeguard']
Logs for rewriting

Does it an expected behavior? How does pytest provide plugins which are needed to be rewritten at the import stage? May be I do something wrong

It should rewrite the conftest files

If it doesn't then we have a bug we missed that needs a additional regression test

testing/test_assertrewrite.py

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…ath to AssertState

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…r plugins

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…r plugins

…s.getcwd

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

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Tusenka · 2025-06-12T13:37:13Z

Do we need to rewrite contest plugins? It's the not original behavior

RonnyPfannschmidt · 2025-06-12T15:10:06Z

Conftest files that are part of the collection should rewrite as far as I remember

RonnyPfannschmidt · 2025-06-12T15:11:20Z

src/_pytest/assertion/__init__.py

@@ -110,8 +110,14 @@ class AssertionState:
    def __init__(self, config: Config, mode) -> None:
        self.mode = mode
        self.trace = config.trace.root.get("assertion")
+        self.config = config


Let's perhaps just pass in the invocation details

Id like to avoid full config in more objects

Hmm. I need to think.
In this case we couldn't change the invocation path for pytester at the simplest way.
The config file is loaded on the initial import stage. Pytester is loaded after that stage and still doesn't know anything about AssertionState.
I need to think what is the best way to do that.

RonnyPfannschmidt · 2025-06-12T16:55:34Z

src/_pytest/assertion/__init__.py

@@ -108,6 +109,19 @@ def __init__(self, config: Config, mode) -> None:
        self.trace = config.trace.root.get("assertion")
        self.hook: rewrite.AssertionRewritingHook | None = None

+    @property


indeed - the rootpath - else we miss imports to rewrite

RonnyPfannschmidt · 2025-06-12T16:59:04Z

src/_pytest/pytester.py

@@ -749,6 +750,13 @@ def chdir(self) -> None:
        This is done automatically upon instantiation.
        """
        self._monkeypatch.chdir(self.path)
+        self._monkeypatch.setattr(


do i gather correct that this bit is to alter the assertion rewtiter state

we should alter only that state, not the full pytest config of the surrounding pytest - this looks like a assertion rewriter shortcoming that needs a followup after this

but we certainly need to alter the assertion hook in sys metapath instead of a pytest config

Pytester doesn't know anything about the AssertionState yet. In order to solve that I need to think in someway how to do this better

We should go with a temporary solution and add a followup issue

RonnyPfannschmidt · 2025-06-12T17:00:02Z

testing/example_scripts/rewrite/venv/pyvenv.cfg

is this a artifact of a missing gitignore?

RonnyPfannschmidt · 2025-06-12T17:01:35Z

my understanding is that rewrite of conftest plugins was always happening as part of the original assertion hooking

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…sertionStatus

Tusenka · 2025-06-13T10:36:48Z

But it still doen't see conftest plugins

Result of provided plugins:
['pytest', 'zope.interface', 'idna', 'anyio', 'sniffio', 'filelock', 'cachetools', 'incremental', 'greenlet', 'pluggy', 'hypothesis', 'Automat', 'wheel', 'virtualenv', 'coverage', 'pip', 'distlib', 'mock', 'pre_commit', 'typing_extensions', 'elementpath', 'pytest-twisted', 'PyYAML', 'pyproject-api', 'identify', 'colorama', 'urllib3', 'hyperlink', 'Pygments', 'sortedcontainers', 'constantly', 'nodeenv', 'xmlschema', 'setuptools', 'attrs', 'requests', 'pytest', 'exceptiongroup', 'decorator', 'platformdirs', 'packaging', 'charset-normalizer', 'cfgv', 'Twisted', 'certifi', 'chardet', 'tox', 'argcomplete', 'iniconfig', 'jaraco.collections', 'zipp', 'typeguard', 'wheel', 'importlib_metadata', 'jaraco.text', 'jaraco.context', 'autocommand', 'tomli', 'typing_extensions', 'more-itertools', 'jaraco.functools', 'packaging', 'platformdirs', 'inflect', 'backports.tarfile']

The conftest plugins are loaded after the PEP302/PEP451 import hook considers files to rewrite.
I propose a separate ticket for conftest plugins rewritng.
I'll try to "play" with this.

RonnyPfannschmidt · 2025-06-14T07:30:45Z

testing/test_assertrewrite.py

+        config = pytester.parseconfig()
+        state = AssertionState(config, "rewrite")
+        assert state.invocation_path == str(config.invocation_params.dir)
+        new_rootpath = str(pytester.path / "test")


Please stay with the pathlib api instead of switching to Str and then back

RonnyPfannschmidt · 2025-06-14T07:32:27Z

testing/test_assertrewrite.py

+        self, pytester: Pytester, hook: AssertionRewritingHook, monkeypatch
+    ) -> None:
+        """If test files contained outside the rootpath, then skip them"""
+        pytester.makepyfile(


It should rewrite the conftest files

If it doesn't then we have a bug we missed that needs a additional regression test

RonnyPfannschmidt · 2025-06-14T07:35:27Z

src/_pytest/pytester.py

@@ -749,6 +750,13 @@ def chdir(self) -> None:
        This is done automatically upon instantiation.
        """
        self._monkeypatch.chdir(self.path)
+        self._monkeypatch.setattr(


We should go with a temporary solution and add a followup issue

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Pytest doen't rewrite conftes plugins #13517

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Disable assertion rewriting external modules #13421

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