trial warning reporting uses print to stdout

[exarkun]

See twisted/trial/runner.py:780-784

Using print means that the warning might not actually be reported, since print can fail with EINTR. It also means that what was once structured information (this is a warning, this is the message format string, these are the arguments) becomes unstructured data in a log file; sometimes this is desirable, but it should probably be up to a reporter what is done with the message, not the runner.

[glyph]

See duplicate #3070

[glyph]

See related ticket #2365

[exarkun]

#3433 was a duplicate of this.

[exarkun]

(In [25279]) Merge flushwarnings-3487

Author: radix, itamar, exarkun Reviewer: glyph Fixes: #3487 Fixes: #3427 Fixes: #2820 Fixes: #3506

Introduce TestCase.flushWarnings, an API for interacting with the Python warnings module in unit tests. By default, the default trial reporter will write warnings emitted by tests to its output stream (no longer does the runner print them to stdout). flushWarnings may be used to prevent this from happening in particular tests, and its return value may be used to make assertions about what warnings have been emitted. TestCase.assertWarns and TestCase.callDeprecated are both now implemented in terms of this more flexible API.

The default reporter includes rudamentary support for duplicate suppression: each warning will be reported only once per test, but if a warning is emitted by two or more tests, it will be reported for each test (isolating tests from each other further by making warning behavior the same regardless of what other tests have run).

There is also some support for failing tests based on warnings emitted. If the Python warnings filters system is used to turn a warning into an exception, any test which causes such a warning to be emitted will have an error attributed to it.

[exarkun]

Apparently this wasn't really fixed. :(

exarkun@charm:~$ trial twisted.test.test_log.LogTest.test_showwarning
twisted.test.test_log
  LogTest
    test_showwarning ... warning-filename.py:27: FakeWarning: unique warning message
                                                  [OK]

-------------------------------------------------------------------------------
Ran 1 tests in 0.002s

PASSED (successes=1)
exarkun@charm:~$ 

[jonathanj]

(In [27219]) Branching to 'leaky-warnings-2820'

[jonathanj]

(In [27220]) Make log.showwarning a method of LogPublisher and use a private log publisher for test_showwarning, to avoid other observers from polluting stdout, refs #2820.

[exarkun]

Okay, great. It looks like this ticket was mostly resolved by the previous branch. Only the tests needed the slight tweak in this new branch to avoid spitting ugly crap into the output. The change makes sense and looks good. Please update the copyright date on both modified files and then merge.

[jonathanj]

(In [27224]) Update copyright dates, refs #2820.

[jonathanj]

(In [27225]) Update the other copyright date, refs #2820.

[jonathanj]

(In [27226]) Merge leaky-warnings-2820 branch.

Author: jonathanj Revewer: exarkun Fixes: #2820

Tweak the tests for "showwarning" to avoid emitting a log message to all the normal observers, some of which simply print warnings to stdout, causing ugly spew in trial's output.