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Fix Config.get_terminal_writer() crash when terminalreporter is unregistered #14378

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Fix Config.get_terminal_writer() crash when terminalreporter is unregistered #14378

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1 change: 1 addition & 0 deletions AUTHORS
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Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,7 @@ Anna Tasiopoulou
Anthon van der Neut
Anthony Shaw
Anthony Sottile
Antoine Leclair
Anton Grinevich
Anton Lodder
Anton Zhilin
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1 change: 1 addition & 0 deletions changelog/14377.bugfix.rst
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@@ -0,0 +1 @@
Fixed :meth:`pytest.Config.get_terminal_writer` crashing with an internal ``AssertionError`` when the terminal reporter plugin has been unregistered (for example, by :pypi:`pytest-tap` in streaming mode). A fresh terminal writer is now created on demand.
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@bluetech bluetech Apr 11, 2026

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The get_terminal_writer function is private, so you can't ref it. Also, let's remove the last sentence describing the solution since that's not relevant for a changelog.

Suggested change
Fixed :meth:`pytest.Config.get_terminal_writer` crashing with an internal ``AssertionError`` when the terminal reporter plugin has been unregistered (for example, by :pypi:`pytest-tap` in streaming mode). A fresh terminal writer is now created on demand.
Fixed a crash from `Config.get_terminal_writer` when the terminalreporter plugin has been unregistered (for example, by :pypi:`pytest-tap` in streaming mode).

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@antoineleclair antoineleclair Apr 13, 2026

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Thanks @bluetech.

I would rather look at removing the dependency on TerminalWriter from assertrepr_compare.

I think you're right. I was proposing a solution, mostly to highlight the problem and in case the solution would be acceptable (after all... it's crashing without the change, and it's not crashing with the change).

Let me know if you want to try it, if not, I'll try looking into it myself.

I think you have more knowledge of the code base and will do a better job with less effort. So if you're OK, I'd leave that one to you. We can close the PR whenever you want.

Or I may try to tackle it in a few months if I see it's still not been touched (which would be totally understandable).

Thank you for your time.

3 changes: 2 additions & 1 deletion src/_pytest/config/__init__.py
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Expand Up @@ -1173,7 +1173,8 @@ def get_terminal_writer(self) -> TerminalWriter:
terminalreporter: TerminalReporter | None = self.pluginmanager.get_plugin(
"terminalreporter"
)
assert terminalreporter is not None
if terminalreporter is None:
return create_terminal_writer(self)
return terminalreporter._tw

def pytest_cmdline_parse(
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23 changes: 23 additions & 0 deletions testing/test_assertion.py
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Expand Up @@ -1682,6 +1682,29 @@ def test_hello():
)


def test_assertrepr_compare_without_terminalreporter(pytester: Pytester) -> None:
pytester.makeconftest(
"""
import pytest

@pytest.hookimpl(trylast=True)
def pytest_configure(config):
reporter = config.pluginmanager.get_plugin("terminalreporter")
config.pluginmanager.unregister(reporter)
"""
)
pytester.makepyfile(
"""
def test_hello():
assert "actual" == "expected"
"""
)
reprec = pytester.inline_run()
_passed, _skipped, failed = reprec.listoutcomes()
assert len(failed) == 1
assert "assert 'actual' == 'expected'" in str(failed[0].longrepr)


def test_assertrepr_loaded_per_dir(pytester: Pytester) -> None:
pytester.makepyfile(test_base=["def test_base(): assert 1 == 2"])
a = pytester.mkdir("a")
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9 changes: 9 additions & 0 deletions testing/test_config.py
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Expand Up @@ -1386,6 +1386,15 @@ def cleanup_first():

assert report == ["cleanup_first", "raise_1", "raise_2", "cleanup_last"]

def test_get_terminal_writer_without_terminalreporter(
self, pytester: Pytester
) -> None:
from _pytest._io import TerminalWriter

config = pytester.parseconfig()
config.pluginmanager.unregister(name="terminalreporter")
assert isinstance(config.get_terminal_writer(), TerminalWriter)


class TestConfigFromdictargs:
def test_basic_behavior(self, _sys_snapshot) -> None:
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