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 ?

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…ath to AssertState

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nicoddemus

Thanks @Tusenka,

Left some comments, please take a look.

nicoddemus · 2025-05-16T11:26:19Z

changelog/13403.bugfix.rst

@@ -0,0 +1 @@
+Disable assertion rewriting of external modules


Can we elaborate a bit on "external modules" here? This should be written for users scanning the changelog.

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 ?

nicoddemus · 2025-06-01T12:23:58Z

src/_pytest/pytester.py

+            Config.InvocationParams(
+                args=self._request.config.invocation_params.args,
+                plugins=self._request.config.invocation_params.plugins,
+                dir=Path(self._path),
+            ),


Suggested change

Config.InvocationParams(

args=self._request.config.invocation_params.args,

plugins=self._request.config.invocation_params.plugins,

dir=Path(self._path),

),

dataclasses.replace(self._request.config.invocation_params, dir=Path(self._path))

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?

nicoddemus · 2025-06-01T12:27:51Z

testing/test_assertrewrite.py

@@ -1294,6 +1297,34 @@ def test_meta_path():
        )
        assert pytester.runpytest().ret == 0

+    def test_rootpath_base(self, pytester: Pytester, monkeypatch: MonkeyPatch) -> None:
+        """Base cases for get rootpath from AssertionState"""


The test name and docstring are a bit confusing to me, why "base cases"? Isn't this test just testing the AssertState.rootpath property?

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.

nicoddemus · 2025-06-01T12:43:43Z

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(


My previous suggestion about using a real-case scenario makes this test unnecessary.

nicoddemus · 2025-06-01T12:43:50Z

testing/test_assertrewrite.py

+        with mock.patch.object(hook, "fnpats", ["*.py"]):
+            assert hook.find_spec("conftest") is not None
+
+    def test_assert_rewrite_correct_for_plugins(


My previous suggestion about using a real-case scenario makes this test unnecessary.

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

psf-chronographer bot added the bot:chronographer:provided (automation) changelog entry is part of PR label May 13, 2025

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WIP! Disable assertion rewriting of external modules #13443

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		@@ -0,0 +1 @@
		Disable assertion rewriting of external modules

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Disable assertion rewriting external modules #13421

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