Pytest's caplog fixture doesn't seem to work

[dougthor42]

Summary

Pytest's caplog fixture is a critical part of testing. I'd love to move to loguru, but loguru doesn't seem to work with caplog.

I'm not sure if this is user error (perhaps it's documented somewhere? I haven't been able to find it.), if it is some design oversight/choice, or if the problem is actually on pytest's end.

Expected Result

Users should be able to use loguru as a drop-in replacement for the stdlib logging package and have tests that use the caplog fixture still work.

Actual Result

Drop-in replacement causes tests that use the caplog pytest fixture to fail.

Steps to Reproduce

Base test file

# test_demo.py
import pytest
import logging
logger = logging.getLogger()
logger.addHandler(logging.StreamHandler())
# from loguru import logger

def some_func(a, b):
    if a < 1:
        logger.warning("Oh no!")
    return a + b

def test_some_func_logs_warning(caplog):
    assert some_func(-1, 2) == 1
    assert "Oh no!" in caplog.text

if __name__ == "__main__":
    some_func(-1, 1)
    print("end")

Without Loguru:

$ python test_demo.py
Oh no!
end
(.venv) Previous Dir: /home/dthor
09:59:56 dthor@Thorium /home/dthor/temp/loguru
$ pytest
========================== test session starts ==========================
platform linux -- Python 3.6.7, pytest-4.3.0, py-1.8.0, pluggy-0.8.1
rootdir: /home/dthor/temp/loguru, inifile:
collected 1 item

test_demo.py .                                                    [100%]

======================= 1 passed in 0.03 seconds ========================

With Loguru:

Adjust test_demo.py by commenting out stdlib logging and uncommenting loguru:

...
# import logging
# logger = logging.getLogger()
# logger.addHandler(logging.StreamHandler())
from loguru import logger
...

$ python test_demo.py
2019-02-22 10:02:35.551 | WARNING  | __main__:some_func:9 - Oh no!
end
(.venv) Previous Dir: /home/dthor
10:02:35 dthor@Thorium /home/dthor/temp/loguru
$ pytest
========================== test session starts ==========================
platform linux -- Python 3.6.7, pytest-4.3.0, py-1.8.0, pluggy-0.8.1
rootdir: /home/dthor/temp/loguru, inifile:
collected 1 item

test_demo.py F                                                    [100%]

=============================== FAILURES ================================
______________________ test_some_func_logs_warning ______________________

caplog = <_pytest.logging.LogCaptureFixture object at 0x7f8e8b620438>

    def test_some_func_logs_warning(caplog):
        assert some_func(-1, 2) == 1
>       assert "Oh no!" in caplog.text
E       AssertionError: assert 'Oh no!' in ''
E        +  where '' = <_pytest.logging.LogCaptureFixture object at 0x7f8e8b620438>.text

test_demo.py:14: AssertionError
------------------------- Captured stderr call --------------------------
2019-02-22 10:02:37.708 | WARNING  | test_demo:some_func:9 - Oh no!
======================= 1 failed in 0.20 seconds ========================

Version information

$ python --version
Python 3.6.7
(.venv) Previous Dir: /home/dthor
10:10:03 dthor@Thorium /home/dthor/temp/loguru
$ pip list
Package                Version
---------------------- -----------
ansimarkup             1.4.0
atomicwrites           1.3.0
attrs                  18.2.0
better-exceptions-fork 0.2.1.post6
colorama               0.4.1
loguru                 0.2.5
more-itertools         6.0.0
pip                    19.0.3
pkg-resources          0.0.0
pluggy                 0.8.1
py                     1.8.0
Pygments               2.3.1
pytest                 4.3.0
setuptools             40.8.0
six                    1.12.0
(.venv) Previous Dir: /home/dthor
10:10:07 dthor@Thorium /home/dthor/temp/loguru
$ uname -a
Linux Thorium 4.4.0-17763-Microsoft #253-Microsoft Mon Dec 31 17:49:00 PST 2018 x86_64 x86_64 x86_64 GNU/Linux
(.venv) Previous Dir: /home/dthor
10:11:33 dthor@Thorium /home/dthor/temp/loguru
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.2 LTS
Release:        18.04
Codename:       bionic

[Delgan]

Lovely bug report, thanks! 😃

I guess the caplog fixture makes use of the standard logging module to capture output. However, as loguru doesn't rely on the logging module and instead implement its own loggers / handlers manager, caplog is not notified of new log entries. For this reason, I don't think there is much I can do about it.

I can think of three possible solutions, but this should be done on the user side:

• Replace caplog with capsys (but may conflict with actual expected output in stderr / stdout)
• Replace caplog with a custom fixture which adds a caputring sink to Loguru's logger
• Add a sink to Loguru's logger in conftest.py which would propagate logs to a standard logging logger

What do you think?

[dougthor42]

Ah, I wasn't aware the loguru didn't use the stdlib logging module. I guess I could have checked that first...

Anyway, between the 3 I'm thinking the easiest one would be the 3rd option. I'll see what I can come up with and, if I find something, submit a PR to update docs with the results.

[Delgan]

Ah, I wasn't aware the loguru didn't use the stdlib logging module. I guess I could have checked that first...

Well, this is actually not stated explicitly anywhere as far as I know. Good catch, I should add a word about this.

Anyway, between the 3 I'm thinking the easiest one would be the 3rd option. I'll see what I can come up with and, if I find something, submit a PR to update docs with the results.

Would fit pretty well in the documentation page about migrating from logging to loguru I think.

Do you think using the sample in the Readme would work for your tests?

class PropagateHandler(logging.Handler):
    def emit(self, record):
        logging.getLogger(record.name).handle(record)

logger.add(PropagateHandler(), format="{message}")

[dougthor42]

Do you think using the sample in the Readme would work for your tests?

I'll look into it. I was actually just writing up a quick update with the following that works to first order.:

import pytest
import logging
_logger = logging.getLogger()
from loguru import logger

def handle(msg):
    # Convert to the loglevel, assume DEBUG for TRACE and SUCCESS custom levels.
    level = getattr(logging, msg.record['level'], 10)
    message = msg.record['message']
    _logger.log(level, message)

# add a sink to logger to propogate lots to standard logging logger.
logger.add(handle)

... # rest of the code from this Issue

[dougthor42]

Looks like adding this to conftest.py works:

import logging

import pytest
from _pytest.logging import caplog as _caplog

from loguru import logger

@pytest.fixture
def caplog(_caplog):
    class PropogateHandler(logging.Handler):
        def emit(self, record):
            logging.getLogger(record.name).handle(record)
    logger.add(PropogateHandler(), format="{message}")
    yield _caplog

Technically you don't even need to add from _pytest.logging import caplog as _caplog and can just:

@pytest.fixture
def caplog(caplog):

but I really don't like that naming collision.

I'll write up some docs for it come Monday or Tuesday and submit the PR. Discussion can continue there.

[Delgan]

That's great, thanks @dougthor42!

I think you should maybe remove() the added sink at the end of each test. Based on your snippet, I'm wondering if this is not addind a new sink each time you run a test.

handler_id = logger.add(PropogateHandler(), format="{message}")
yield _caplog
logger.remove(handler_id)

[dougthor42]

I wasn't able to force it to add multiple sinks, but I agree that explicitly removing it after is the safe way to go. I'll make sure to include that.

[blueyed]

Do you think it makes sense for loguru to ship a pytest plugin that would do this?

(I just came here from the docs, have not read up on it, but think it is possible, and would be willing to do it)

[Delgan]

Hi @blueyed.

Do you think it makes sense for loguru to ship a pytest plugin that would do this?

(I just came here from the docs, have not read up on it, but think it is possible, and would be willing to do it)

Thanks for your proposition. However, I don't wish for Loguru to expose such plugin, the code snippet in the documentation is sufficient enough as a workaround.

[blueyed]

Cool. I might look into this anyway, since the code snippet can be improved in general, and I think it might be useful to expose loguru's data additionally.. will likely come back to this later then.

[Delgan]

@blueyed Improvements of the documentation are much welcome, thanks!

[trallnag]

@dougthor42, is there a way to configure the handler to emit the loguru message without it adding it's own info to the string? What I'm doing atm is the following:

class PropogateHandler(logging.Handler):
        def emit(self, record):
            logging.getLogger(record.name).handle(record)

@pytest.fixture(scope="session", autouse=True)
def setup_logging_for_pytest():
    logger.remove()
    print("hallo")

    _ = logger.add(PropogateHandler(), format=(Unstructured.construct()).fmt)

But my logs end up looking like this:

--------------------------------- Captured Log ---------------------------------
DEBUG    prometheus_adaptive_cards.distribution.utils:utils.py:93 18:13:01 DEBUG utils:extract_url:93 Start to extract url from target config and common attrs. {}
WARNING  prometheus_adaptive_cards.distribution.utils:utils.py:134 18:13:01 WARNING utils:extract_url:134 No URL extracted. {'target': {'url': None, 'expansion_url': 'hallo/{common_labels[namespace]}/fefe', 'url_from_label': None, 'url_from_annotation': None}}
--------------------------------- Captured Out ---------------------------------

[dougthor42]

My guess is that the issue comes from Unstructured.construct() - where are you pulling that from? Can you show me the imports?

[trallnag]

The Unstructured is part of my settings model, I create an instance to get the default format string I use in the actual application. Here are the imports / the conftest itself:

https://github.com/trallnag/prometheus-adaptive-cards/blob/2de6d0d12d1eee8247253a84489cd2855b05c339/tests/conftest.py#L1-L9

import re
from typing import Literal, Optional, Pattern

from loguru import logger
from pydantic import AnyUrl, BaseModel, ValidationError, parse_obj_as, validator

from prometheus_adaptive_cards.config.settings_raw import setup_raw_settings

The settings class:

https://github.com/trallnag/prometheus-adaptive-cards/blob/2de6d0d12d1eee8247253a84489cd2855b05c339/prometheus_adaptive_cards/config/settings.py#L24-L26

class Unstructured(BaseModel):
    fmt: str = "<green>{time:HH:mm:ss}</green> <level>{level}</level> <cyan>{module}:{function}:{line}</cyan> {message} <dim>{extra}</dim>"
    colorize: bool = True

When I try to print the record msg I see the actual string I would like to see. It seems like the .handle() call is the culprit.

class PropogateHandler(logging.Handler):
        def emit(self, record):
            print(record.getMessage())
            logging.getLogger(record.name).handle(record)

[trallnag]

But I guess it's not that big of a deal. When I initialize the logging in the conftest just like I would in my application main and then run pytest from the CLI I can see the logs captured in the stdout section in addition to the mangled logs in the cap log section

[dougthor42]

Ah ok. Yes, your format string looks fine.

Well, I don't know exactly why, but you need to set your formatter on the PropogateHandler rather than on the loguru logger:

class PropogateHandler(logging.Handler):
    def emit(self, record):
        # Set the formatter on the PropogateHandler
        self.setFormatter(logging.Formatter(fmt=Unstructured.construct()).fmt))
        logging.getLogger(record.name).handle(record)

and when adding the sink to loguru, set the format to just the message:

    _ = logger.add(PropogateHandler(), format="{message}")

I wonder if this (setting the PropogateHandler formatter) is the more general solution, meaning docs should be updated.

Full Example

This shows that I'm able to duplicate your results:

# test_2.py
import logging

import pytest
from loguru import logger

# same as Unstructured.construct()).fmt
m = (
    "<green>{time:HH:mm:ss}</green>"
    " <level>{level}</level>"
    " <cyan>{module}:{function}:{line}</cyan>"
    " {message}"
    " <dim>{extra}</dim>"
)

class PropogateHandler(logging.Handler):
    def emit(self, record):
        logging.getLogger(record.name).handle(record)

@pytest.fixture(scope="session", autouse=True)
def setup_logging_for_pytest():
    logger.remove()
    print("hallo")

    _ = logger.add(PropogateHandler(), format=m)

def test_a():
    logger.debug("foo")
    assert False

$ pytest test_2.py
========================================================= test session starts =========================================================
platform linux -- Python 3.6.8, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
rootdir: /home/dthor/temp/loguru-pytest
collected 1 item

test_2.py F                                                                                                                     [100%]

============================================================== FAILURES ===============================================================
_______________________________________________________________ test_a ________________________________________________________________

    def test_a():
        logger.debug("foo")
>       assert False
E       assert False

test_2.py:32: AssertionError
-------------------------------------------------------- Captured stdout setup --------------------------------------------------------
hallo
---------------------------------------------------------- Captured log call ----------------------------------------------------------
DEBUG    test_2:test_2.py:31 11:01:14 DEBUG test_2:test_a:31 foo {}
======================================================= short test summary info =======================================================
FAILED test_2.py::test_a - assert False
========================================================== 1 failed in 0.15s ==========================================================

Make the changes

diff --git a/test_2.py b/test_2.py
index 887804d..4e878c2 100644
--- a/test_2.py
+++ b/test_2.py
@@ -16,6 +16,7 @@ m = (

 class PropogateHandler(logging.Handler):
     def emit(self, record):
+        self.setFormatter(logging.Formatter(fmt=m))
         logging.getLogger(record.name).handle(record)

@@ -24,7 +25,7 @@ def setup_logging_for_pytest():
     logger.remove()
     print("hallo")

-    _ = logger.add(PropogateHandler(), format=m)
+    _ = logger.add(PropogateHandler(), format="{message}")

 def test_a():

And see that things are no longer duplicated:

$ pytest test_2.py
========================================================= test session starts =========================================================
platform linux -- Python 3.6.8, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
rootdir: /home/dthor/temp/loguru-pytest
collected 1 item

test_2.py F                                                                                                                     [100%]

============================================================== FAILURES ===============================================================
_______________________________________________________________ test_a ________________________________________________________________

    def test_a():
        logger.debug("foo")
>       assert False
E       assert False

test_2.py:32: AssertionError
-------------------------------------------------------- Captured stdout setup --------------------------------------------------------
hallo
---------------------------------------------------------- Captured log call ----------------------------------------------------------
DEBUG    test_2:test_2.py:31 foo
======================================================= short test summary info =======================================================
FAILED test_2.py::test_a - assert False
========================================================== 1 failed in 0.15s ==========================================================

[trallnag]

I see, completely missed that we can set the formatter on PropogateHandler itself. But I've run into two issues:

1. What does setting the format of the native Python to a Loguru specific format string do? Can it understand the format?
2. The test script fails with Python 3.9 but works with 3.8.6 and 3.8.12 (checked it in a bare bones venv)

Here's the output:

============================================= FAILURES =============================================
______________________________________________ test_a ______________________________________________

    def test_a():
        logger.debug("foo")
>       assert False
E       assert False

single.py:33: AssertionError
-------------------------------------- Captured stdout setup ---------------------------------------
hallo
--------------------------------------- Captured stderr call ---------------------------------------
--- Logging error in Loguru Handler #1 ---
Record was: {'elapsed': datetime.timedelta(microseconds=14877), 'exception': None, 'extra': {}, 'file': (name='single.py', path='/home/jfn/source/playground/test_loguru_pytest/single.py'), 'function': 'test_a', 'level': (name='DEBUG', no=10, icon='🐞'), 'line': 32, 'message': 'foo', 'module': 'single', 'name': 'single', 'process': (id=943984, name='MainProcess'), 'thread': (id=139993484752704, name='MainThread'), 'time': datetime(2020, 11, 10, 21, 42, 25, 65855, tzinfo=datetime.timezone(datetime.timedelta(seconds=3600), 'CET'))}
Traceback (most recent call last):
  File "/home/jfn/.pyenv/versions/3.9.0/lib/python3.9/site-packages/loguru/_handler.py", line 177, in emit
    self._sink.write(str_record)
  File "/home/jfn/.pyenv/versions/3.9.0/lib/python3.9/site-packages/loguru/_simple_sinks.py", line 60, in write
    self._handler.handle(record)
  File "/home/jfn/.pyenv/versions/3.9.0/lib/python3.9/logging/__init__.py", line 948, in handle
    self.emit(record)
  File "/home/jfn/source/playground/test_loguru_pytest/single.py", line 19, in emit
    self.setFormatter(logging.Formatter(fmt=m))
  File "/home/jfn/.pyenv/versions/3.9.0/lib/python3.9/logging/__init__.py", line 570, in __init__
    self._style.validate()
  File "/home/jfn/.pyenv/versions/3.9.0/lib/python3.9/logging/__init__.py", line 423, in validate
    raise ValueError("Invalid format '%s' for '%s' style" % (self._fmt, self.default_format[0]))
ValueError: Invalid format '<green>{time:HH:mm:ss}</green> <level>{level}</level> <cyan>{module}:{function}:{line}</cyan> {message} <dim>{extra}</dim>' for '%' style
--- End of logging error ---
===================================== short test summary info ======================================
FAILED single.py::test_a - assert False
======================================== 1 failed in 0.07s =========================================

[Delgan]

Hi!

Maybe I can help you clarify. Loguru will first create the string according to it's own format and regardless of the Formatter from standard logging.

logger.add(PropagateHandler(), format="[{{time:HH:mm:ss}}] {message}")
logger.info("Test")
# => '[22:12:08] Test'

Then, the formatted message is sent to the PropogateHandler. To do so, the loguru record is converted to a standard LogRecord.

log_record = LogRecord(msg="[22:12:08] Test", level="INFO", ...)

If no Formatter is assigned to the PropagateHandler, the standard logging will use %(message)s by default and hence display the message according to the loguru format.

Formatter().format(log_record)
# => '[22:12:08] Test'

Supposing you use a custom Formatter, you should make sure that the loguru format is equals to "{message}" to avoid duplication.

Formatter("%(asctime)s %(message)s").format(log_record)
# => '2020-11-10 22:12:08,312 [22:12:08] Test'

However, you can't the loguru formatter style (which uses {}) to configure a standard Formatter (which uses %). Also, the fields does not use the same names ("asctime" != "time").

[trallnag]

What am I even trying to achieve :thinking: Okay so thanks to @Delgan's post I managed to propagate Loguru's formatted message 1:1 to a Python logger which then outputs it to std error and Pytest seems to capture it. Here is the full script based on @dougthor42:

import logging

import pytest
from loguru import logger

# same as Unstructured.construct()).fmt
m = (
    "<green>{time:HH:mm:ss}</green>"
    " <level>{level}</level>"
    " <cyan>{module}:{function}:{line}</cyan>"
    " {message}"
    " <dim>{extra}</dim>"
)

pytest_logger = logging.getLogger("pytest")
ch = logging.StreamHandler()
ch.setFormatter(logging.Formatter('%(message)s'))
pytest_logger.addHandler(ch)
pytest_logger.propagate = False

class PropogateHandler(logging.Handler):
    def emit(self, record):
        pytest_logger.handle(record)

@pytest.fixture(scope="session", autouse=True)
def setup_logging_for_pytest():
    logger.remove()
    _ = logger.add(PropogateHandler(), format=m)

def test_a():
    logger.debug("foo")
    assert False

Notice that I set propagate to False. Without this the logger seems to propagate the record up. And somewhere "up there" the message gets formatted again.

Here is the output:

❯ pytest single.py
======================================= test session starts ========================================
platform linux -- Python 3.9.0, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
rootdir: /home/jfn/source/playground/test_loguru_pytest
collected 1 item

single.py F                                                                                  [100%]

============================================= FAILURES =============================================
______________________________________________ test_a ______________________________________________

    def test_a():
        logger.debug("foo")
>       assert False
E       assert False

single.py:39: AssertionError
-------------------------------------- Captured stdout setup ---------------------------------------
hallo
--------------------------------------- Captured stderr call ---------------------------------------
23:11:04 DEBUG single:test_a:38 foo {}
===================================== short test summary info ======================================
FAILED single.py::test_a - assert False
======================================== 1 failed in 0.06s =========================================

Here is how the output looks like when I enable propagation:

-------------------------------------- Captured stdout setup ---------------------------------------
hallo
--------------------------------------- Captured stderr call ---------------------------------------
23:13:08 DEBUG single:test_a:38 foo {}
---------------------------------------- Captured log call -----------------------------------------
DEBUG    single:single.py:38 23:13:08 DEBUG single:test_a:38 foo {}
===================================== short test summary info ======================================
FAILED single.py::test_a - assert False
======================================== 1 failed in 0.07s =========================================

I don't know why pytest does not recognize it as a log call in the propagation deactivated example, but I'm happy with it ending up in stderr as well. Though I would like to 23:13:08 DEBUG single:test_a:38 foo {} show up below Captured log call

---

Edit: Simplified example a bit

[trallnag]

Okay nevermind Pytest has it's own log format configuration :man_facepalming:

[dougthor42]

What am I even trying to achieve?

It sounds like you're just interested in having pytest capture log output on failures. Is that correct? If so, none of this PropogateHandler mumbo jumbo needs to be done - pytest will already capture loguru output for tests. The "Captured stderr call" section might not be formatted the same way, but I don't know if that matters to you.

from loguru import logger

def test_foo():
    print("hallo")
    logger.debug("foo")
    assert False

$ pytest test_foo.py
============================================ test session starts =============================================
platform linux -- Python 3.6.8, pytest-6.1.2, py-1.9.0, pluggy-0.13.1
rootdir: /home/dthor/temp/loguru-pytest
collected 1 item

test_foo.py F                                                                                          [100%]

================================================== FAILURES ==================================================
__________________________________________________ test_foo __________________________________________________

    def test_foo():
        print("hallo")
        logger.debug("foo")
>       assert False
E       assert False

test_foo.py:6: AssertionError
-------------------------------------------- Captured stdout call --------------------------------------------
hallo
-------------------------------------------- Captured stderr call --------------------------------------------
2020-11-10 14:32:31.733 | DEBUG    | test_foo:test_foo:5 - foo
========================================== short test summary info ===========================================
FAILED test_foo.py::test_foo - assert False
============================================= 1 failed in 0.14s ==============================================

The core of this issue is specific to pytest's caplog fixture, which you only need if you want to assert what's being logged. Meaning, you need the PropogateHandler if you want to do this:

from loguru import logger

def test_foo(caplog):
    print("hallo")
    logger.debug("foo")
    assert "foo" in caplog.text"     # This won't work without the PropogateHandler hack

[SomeAkk]

Hello, i am also have problems with pytest and loguru when try to test function with @logger.catch decorator. That function can throw exception and by that i need to write some log message. Also I need to test it: want to check if tested function throw any exception.

# tested_function.py
from loguru import logger

@logger.catch(message="oops!", default=False)
def tested_function(a: int, b: int) -> int:
    return a/b

Now when i try to write test, i also get exceptions like theme author:

# test_tested_function.py
import pytest

def test():
    with pytest.raises(Exception):
        _ = tested_function(9, 0)

Also as @dougthor42 mentioned, commenting of @logger.catch(... help to test function. I try to add conftest.py to my test directory with code example like in docs, but that not helped at all.

Maybe for my task i need PropogateHandler hack too ... Or i added conftest.py not in proper places in project and by that this not work ...

Can you give some hint for me:

1. where to add conftest.py or PropogateHandler?
2. how to call PropogateHandler or fixture from conftest.py to make test() working?

[Delgan]

Hi @SomeAkk.

The catch() decorator does not propagate exceptions by default. It will simply create a logging record and send it to the handlers as any other logged message. You need to specify reraise=True if you want to be able to explicitly catch it with try / except or with pytest.raises().

However, a little hack is possible to achieve what you want. That is, having a behavior similar to reraise=False in production but being able to switch to reraise=True during testing. Since the message is sent to each configured handler, you can add an error_handler() sink that will be in charge of re-raising the error. Be careful, it must also be added with the parameter catch=False parameter because Loguru prevents otherwise the propagation of the error.

def error_handler(message):
    exc = message.record["exception"]
    if exc is not None:
        _, val, _ = exc
        raise val

# Add this during testing
logger.add(error_handler, catch=False)

[SomeAkk]

@Delgan looks great - test is passed, thx for that hack

One minor problem that all error backtrace is fall in std, but not critical at all i thing:

============================= test session starts ==============================
platform darwin -- Python 3.7.9, pytest-5.4.3, py-1.9.0, pluggy-0.13.1 -- /Users/SomeAkk/...
cachedir: .pytest_cache
rootdir: ...
collecting ... collected 1 item

test_tested_function.py::Test::test PASSED                   [100%]

2020-12-04 18:26:04.582 | ERROR    | test_tested_function:61 - oops!
Traceback (most recent call last):

  File "/Applications/PyCharm.app/.../_jb_pytest_runner.py", line 43, in <module>
    sys.exit(pytest.main(args, plugins_to_load + [Plugin]))
    │   │    │      │    │     │                  └ <class '__main__.Plugin'>
    ...
    ... traceback ...
    ...

  ZeroDivisionError: ...

============================== 1 passed in 0.28s ===============================

Process finished with exit code 0

[Delgan]

@SomeAkk Maybe that is because of the other configured handler that you would first need to remove()?

[alextremblay]

Thank you all for code samples, they're incredibly useful. I just want to share my own, in case any of you find it useful:

# conftest.py
import logging

import pytest
from loguru import logger

@pytest.fixture
def caplog(caplog):
    """
    override and wrap the caplog fixture with one of our own
    """
    logger.remove() # remove default handler, if it exists
    logger.enable("") # enable all logs from all modules
    logging.addLevelName(5, "TRACE") # tell python logging how to interpret TRACE logs
    class PropogateHandler(logging.Handler):
        def emit(self, record):
            logging.getLogger(record.name).handle(record)
    logger.add(PropogateHandler(), format="{message} {extra}", level="TRACE") # shunt logs into the standard python logging machinery
    caplog.set_level(0) # Tell logging to handle all log levels
    yield caplog

[Delgan]

Please, note the documentation has been updated. The recommended way to integrate Loguru with pytest is to override the caplog fixture this way:

@pytest.fixture
def caplog(caplog):
    handler_id = logger.add(caplog.handler, format="{message}")
    yield caplog
    logger.remove(handler_id)

Using PropagateHandler could result in dead-lock if inadvertently combined with InterceptHandler see #474.

[benjamin-kirkbride]

I am trying to use this with multiprocessing, but am not having any luck. Is there something I should be looking out for there?

[n05tr0m0]

Please, note the documentation has been updated. The recommended way to integrate Loguru with pytest is to override the caplog fixture this way:

@pytest.fixture
def caplog(caplog):
    handler_id = logger.add(caplog.handler, format="{message}")
    yield caplog
    logger.remove(handler_id)

Using PropagateHandler could result in dead-lock if inadvertently combined with InterceptHandler see #474.

@Delgan Thank you so much! Your snippet helped me avoid deadlock!

[glass-ships]

Please, note the documentation has been updated. The recommended way to integrate Loguru with pytest is to override the caplog fixture this way:

@pytest.fixture
def caplog(caplog):
    handler_id = logger.add(caplog.handler, format="{message}")
    yield caplog
    logger.remove(handler_id)

Using PropagateHandler could result in dead-lock if inadvertently combined with InterceptHandler see #474.

So I've added this snippet to my conftest.py as suggested in the docs, but I notice some interesting behavior where the logger clearly emits the proper level of log, and the expected content, but for some reason is not being interpreted as such by caplog.

Pytest Errors

```python > assert caplog.records[0].levelname == 'WARNING' E AssertionError: assert 'DEBUG' == 'WARNING' E - WARNING E + DEBUG tests/unit/test_csvreader.py:64: AssertionError ----------------------------------- Captured stderr call ----------------------------------- 2023-03-28 19:20:50 | WARNING | koza.io.reader.csv_reader | Additional column(s) in source file csv file {'combined_score'} Checking if new column(s) inserted at end of the row ... > assert caplog.records[1].msg.startswith( 'Additional columns located within configured fields' ) E assert False E + where False = ('Additional columns located within configured fields') E + where = "Additional column(s) in source file csv file\n\t{'cooccurence'}\n\tChecking if new column(s) inserted at end of the row".startswith E + where "Additional column(s) in source file csv file\n\t{'cooccurence'}\n\tChecking if new column(s) inserted at end of the row" = .msg tests/unit/test_csvreader.py:75: AssertionError ----------------------------------- Captured stderr call ----------------------------------- 2023-03-28 19:20:50 | WARNING | koza.io.reader.csv_reader | Additional column(s) in source file csv file {'cooccurence'} Checking if new column(s) inserted at end of the row 2023-03-28 19:20:50 | WARNING | koza.io.reader.csv_reader | Additional columns located within configured fields given: ['protein1', 'protein2', 'neighborhood', 'fusion', 'coexpression', 'experimental', 'database', 'textmining', 'combined_score'] found: ['protein1', 'protein2', 'neighborhood', 'fusion', 'cooccurence', 'coexpression', 'experimental', 'database', 'textmining', 'combined_score'] additional columns: {'cooccurence'} ```

I did try to print some contents of caplog to stdout, and apart from the wrong level, it seems like the message is being parsed as not a string?

caplog.records[0].msg: headers for csv file parsed as ['protein1', 'protein2', 'neighborhood', 'fusion', 'cooccurence', 'coexpression', 'experimental', 'database', 'textmining', 'combined_score'] 

caplog.records[0].levelname: DEBUG

[Delgan]

@glass-ships Please open a new issue with fully reproducible example if possible.

[pokop]

By the way, there is a plugin for that: https://github.com/mcarans/pytest-loguru