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implement a --suppress-logger option to logging to suppress logging for one or multiple loggers #7873

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implement a --suppress-logger option to logging to suppress logging for one or multiple loggers #7873

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3dc6553
adding ability to disable certain loggers from propagating or writing…
symonk Oct 7, 2020
d28680a
initial work on --suppress-logger
symonk Oct 7, 2020
c8df5cb
assert using the caplog fixture correctly & assert stderr when writin…
symonk Oct 7, 2020
73fb810
add changelog entry; improve unit tests
symonk Oct 7, 2020
4806af7
use self._config of the LoggingPlugin instead of passing it explicitly
symonk Oct 7, 2020
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1 change: 1 addition & 0 deletions changelog/7431.feature.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
``--suppress-logger`` CLI option added to suppress output from individual loggers
18 changes: 18 additions & 0 deletions src/_pytest/logging.py
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,13 @@ def add_option_ini(option, dest, default=None, type=None, **kwargs):
default=None,
help="Auto-indent multiline messages passed to the logging module. Accepts true|on, false|off or an integer.",
)
group.addoption(
"--suppress-logger",
action="append",
default=[],
dest="suppress_logger",
help="Suppress loggers by name",
)


_HandlerType = TypeVar("_HandlerType", bound=logging.Handler)
Expand Down Expand Up @@ -575,6 +582,17 @@ def __init__(self, config: Config) -> None:
get_option_ini(config, "log_auto_indent"),
)
self.log_cli_handler.setFormatter(log_cli_formatter)
if config.option.suppress_logger:
self._suppress_loggers()

def _suppress_loggers(self) -> None:
logger_names = set(self._config.option.suppress_logger)
for name in logger_names:
# disable propagation for the given logger preventing of event passing to ancestor handlers
# adding a NullHandler to prevent logging.LastResort handler from logging warnings to stderr
logger = logging.getLogger(name)
logger.addHandler(logging.NullHandler())
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unsure about this

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Not sure myself, but what happens to other handlers that are installed in the logger? I suppose they will still process messages?

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@symonk symonk Oct 8, 2020 •
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Interesting one, from a quick check it will still use such handlers, this is outlined below:

>>> import logging
>>> log = logging.getLogger('pytest')
>>> log.setLevel(logging.DEBUG)
>>> # add a stream handler to stderr by default
>>> log.addHandler(logging.StreamHandler())
>>> log.debug('stderr')
stderr
>>> log.addHandler(logging.NullHandler())
>>> log.debug('does this still write to stderr')
does this still write to stderr

two questions:

  • Should we iterate / remove the handlers on the given logger?
  • Should we check the hierarchy of loggers if the logger provided exists, else I assume its going to register a new one by badly typed --suppress-logger names into the hierarchy dict (maybe thats not a big deal)

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@symonk symonk Oct 8, 2020 •
edited
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#1 check name is in: 
logs = [logging.getLogger(name).name for name in logging.root.manager.loggerDict] ?

#2 empty logger handlers for the given logger, unsure of the implications here
logger.handlers = [logging.NullHandler()]

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What we do to suppress logs of certain loggers is to simply set the logLevel of those loggers to CRITICAL. Have you thought about doing that?

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@symonk symonk Oct 8, 2020 •
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No I didn’t think about that as I was thinking about fully suppressing any level, however doing something like that may be better suited as I’d assume even users who wanted this feature would/should actually care about such messages from those libraries etc. Feels like a nice middle ground, thoughts?

logger.propagate = False

def _create_formatter(self, log_format, log_date_format, auto_indent):
# Color option doesn't exist if terminal plugin is disabled.
Expand Down
57 changes: 57 additions & 0 deletions testing/logging/test_reporting.py
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Expand Up @@ -1152,3 +1152,60 @@ def test_log_file_cli_subdirectories_are_successfully_created(testdir):
result = testdir.runpytest("--log-file=foo/bar/logf.log")
assert "logf.log" in os.listdir(expected)
assert result.ret == ExitCode.OK


def test_suppress_loggers(testdir):
testdir.makepyfile(
"""
import logging
import os
suppressed_log = logging.getLogger('suppressed')
other_log = logging.getLogger('other')
normal_log = logging.getLogger('normal')
def test_logger_propagation(caplog):
with caplog.at_level(logging.DEBUG):
suppressed_log.warning("no log; no stderr")
other_log.info("no log")
normal_log.debug("Unsuppressed!")
print(os.linesep)
assert caplog.record_tuples == [('normal', 10, 'Unsuppressed!')]
"""
)
result = testdir.runpytest(
"--suppress-logger=suppressed", "--suppress-logger=other", "-s"
)
assert result.ret == ExitCode.OK
assert not result.stderr.lines


def test_suppress_loggers_help(testdir):
result = testdir.runpytest("-h")
result.stdout.fnmatch_lines(
[" --suppress-logger=SUPPRESS_LOGGER", "*Suppress loggers by name*"]
)


def test_log_suppressing_works_with_log_cli(testdir):
testdir.makepyfile(
"""
import logging
log = logging.getLogger('mylog')
suppressed_log = logging.getLogger('suppressed')
def test_log_cli_works(caplog):
log.info("hello world")
suppressed_log.warning("Hello World")
"""
)
result = testdir.runpytest(
"--log-cli-level=DEBUG",
"--suppress-logger=suppressed",
"--suppress-logger=mylog",
)
assert result.ret == ExitCode.OK
result.stdout.no_fnmatch_line(
"INFO mylog:test_log_suppressing_works_with_log_cli.py:5 hello world"
)
result.stdout.no_fnmatch_line(
"WARNING suppressed:test_log_suppressing_works_with_log_cli.py:6 Hello World"
)
assert not result.stderr.lines