Print captured logs before entering pdb

[brianmaissy]

Extension of PR #3186 for the caplog feature.

When a test fails and we are about the enter the debugger, we first print the traceback and the captured stdout and stderr. We need to add the captured logs. This is being opened as a separate ticket because caplog was added in the features branch, so if this issue is fixed before it gets merged, target the features branch for this issue as well.

See discussion here: https://github.com/pytest-dev/pytest/pull/3186/files#r166777807

[brianmaissy]

@nicoddemus @Thisch So do you think we should still print captured logs at the end when live logging is on? It seems to me that as long as we capture something we should print it. Live logging is in addition to capturing, because if it's on we get the logs as they happen and also in the report if the test fails. I think the behavior before entering the debugger should parallel the failed test report.

[twmr]

I have some long running tests, which output a lot of log messages when I debug them. For debugging I use live-logging and --pdb. This allows me to abort the tests when I spot sth suspicious in the live-logs while the test is running).

For me it does not make sense to show the captured logs before entering pdb, since

1) the captured logs are not colored. IMO the captured logs are not as readable as the colored live-logs (see #3142).
2) the large number of logs generated by my tests is displayed twice (first the live-logs then the captured logs).

For the test reports it is possible to disable the printing of caught logs on failure (--no-print-logs). AFAIK this is not possible for the captured stdout/stderr, right (@Niccodemus)? --no-print-logs is not taken into account in your PR #3210.

It might make sense to only display the captured logs before entering pdb when --no-print-logs is not given.

WDYT?

[brianmaissy]

Sounds good, I'll modify it to take into consideration the --no-print-logs option

[nicoddemus]

Thanks @Thisch for the explanation, indeed it makes sense to consider --no-print-logs to not print the logs in that case. 👍

[twmr]

BTW I would suggest to introduce a new generic --no-captured-output option and deprecate the --no-print-logs option. The --no-captured-output option disables the printing of captured output (stdout, stderr and logs) on failure and can also be used in the "enter pdb" code in #3186 and #3210.

[nicoddemus]

@Thisch I think this should go in a separate issue, would you mind opening it? Thanks!

[twmr]

Given that we've merged #3234, we can close this issue.