caplog.clear() removes records but leaves collected .text

[ankostis]

Problem

Currently (see pytest versions below), method LogCaptureHandler.clear() removes all records from the handler, but it does not clear the collected text in it's .stream, leading to contradictory results:

pytest/_pytest/logging.py

Lines 240 to 244 in 07e768a

	def clear(self):
	"""Reset the list of log records."""
	self.handler.records = []

pytest/_pytest/logging.py

Lines 220 to 224 in 07e768a

	@property
	def text(self):
	"""Returns the log text."""
	return self.handler.stream.getvalue()

Example

import logging

def test_caplog_clear(caplog):
    rlog = logging.getLogger()

    rlog.error("Hi there!")
    assert "Hi there!" in caplog.text

    caplog.clear()
    assert all("Hi there!" not in r for r in caplog.records)
    assert "Hi there!" not in caplog.text  # Fails!

Suggestion

One can either add this line into .clear():

self.handler.stream = py.io.TextIO()

OR add this one, which will work also for clients holding handler's stream property:

self.handler.stream.truncate(0)

Versions

pip list |grep pytest
pytest (3.4.2)
pytest-cov (2.5.1)
pytest-cover (3.0.0)
pytest-coverage (0.0)
pytest-mock (1.7.1)
pytest-runner (4.0)

[pytestbot]

GitMate.io thinks possibly related issues are #3037 (caplog fixture: capture log records from another process), #891 (remove named marker attributes and collect markers in items), #3080 (Remove pytest_namespace), #3083 (Remove metafunc.addcall), and #3079 (Remove yield tests).

[nicoddemus]

OR add this one, which will work also for clients holding handler's stream property:

This seems like a nice solution (@Thisch what do you think?). @ankostis you have done some researching here, would you like to work on a PR? Sorry nevermind, only now I noticed that @Thisch has already self-assigned this issue. 😉

[twmr]

I'm for reinitializing the stream, hence not using truncate. See https://stackoverflow.com/questions/4330812/how-do-i-clear-a-stringio-object#4330829

@ankostis If you want to work on this I can unassign myself. (I'll probably not have time to work on it soon)

[ankostis]

I'll give it a try.

[twmr]

You can take a look at my commit (62b224b)

[ankostis]

Done

[ankostis]

Oups, i see now my changelog change is forbiden. Rewritting history without it.

Use this if useful:

- Fix ``clear()`` method on ``caplog`` fixture which cleared only the ``records``,
  and not the ``text```property. (`#3297
  <https://github.com/pytest-dev/pytest/issues/3297>`_)

[nicoddemus]

Oups, i see now my changelog change is forbiden

Hmm it seems your markup around text has an extra backtick and failed to parse. Also don't need to add the link to #3297 because this is added automatically.

I suggested a changelog entry on my review because I did not see your comment here, so feel free to use your initial take instead of mine:

Fixed ``clear()`` method on ``caplog`` fixture which cleared only the ``records`` attribute but not the ``text`` property.