[py-dev] Log to a file

[holger krekel]

Hi Simon,

i finally got around to look at your plugin ...

On Thu, Oct 29, 2009 at 17:42 +1100, Simon wrote:
> On 28/10/2009, at 19:44 , holger krekel holger-at-merlinux.eu |py-dev + 
> execnet-dev| wrote:
>
>>> Hi Holger,
>>>
>>> I started looking into this a bit but ran into a problem when I
>>> started to probe the py.io module.
>>>
>>> I tried running the py.io examples on the website <http://codespeak.net/py/dist/io.html
>>>> but when I run the py.io.StdCaptureFD example, python dies on the
>>> second line:
>>>
>>> stakita at okum:~$ python
>>> Python 2.6.2 (release26-maint, Apr 19 2009, 01:56:41)
>>> [GCC 4.3.3] on linux2
>>> Type "help", "copyright", "credits" or "license" for more  
>>> information.
>>> History restored: /auto/home/stakita/.pyhistory, Max Length: 500
>>>>>> import py, sys
>>>>>> capture = py.io.StdCaptureFD()
>>
>> The redirect here happens for stdout, stderr and stdin is put to
>> /dev/zero on the file descriptor level ...
>>
>>> stakita at okum:~$
>>
>> ... so the python interpreter immediately gets an EOL on stdin and  
>> dies.
>
> So does this mean that the example is a bit broken then?

yes, i fixed it in trunk. 

>>> My guess is that an exception is being thrown, but the captured
>>> sys.stderr descriptor is not passing any meaningful traceback.
>>
>> you can call py.io.StdCaptureFD(err=True, in_=False,
>> out=False) and should be able to play with writing to stderr.
>>
>>> I tried wrapping the call in try/except, but that didn't seem to  
>>> help.
>>> On the positive side, the problem appears to be quite reproducible.
>>>
>>> Any ideas on what is going on here?
>>
>> just anoter recommendation.  Maybe it is easiest for you to implement
>> a "--iocapturelog=filename" option and see to send output to
>> it from the pytest_capture plugin on the py-trunk repository.
>> You can start experimenting by copying the pytest_capture.py
>> file somewhere into your import path and modifying it.  Your
>> local version will override the builtin one.
>>
>> HTH,
>> holger
>
> Thanks for the suggestion, and here is a first pass. Attached is a  
> modified version of pytest_capture.py from the 1.0.2 release.
>
> In this file, I just push the options into the CaptureManager so that  
> the command line args are available. This does mean that the config file 
> options stuff is not hooked up, but at least it works from the command 
> line at the moment.

just using "config.getvalue()" should be fine.  "py.test --help-config" 
then shows the derived ENV/conftest.py settings, btw. 

> Additional plugin command line options are:
>     --log-file <filename>
>         When used with the two capture options ('fd' and 'sys') this  
> will enable pushing the stdout and stderr writes to the specified file.
>     --append-log
>         This allows appending to the file as opposed to the default  
> clobber behaviour.
>
> Does this fit with your model of how the plugin should be structured?

roughly, yes :)

some small comments:

* the "append-log" option i'd rather encode as "+logfilename"
  for the capture-file option  (goal is to minimize number of cmdline args)
  just one --capture-file option makes sense 

* "self.logfd" is actually a file object, not a file descriptor, so better use
  "self.capture_file" or so. 

* your code is not Python3 compatible 

I'd like to include your changes ... could you rework your
patch by checking out http://bitbucket.org/hpk42/py-trunk 
and modifying 

    _py/test/plugin/pytest_capture.py

and running and adding tests here:

    testing/pytest/plugin/test_pytest_capture.py

?  

FYI on linux/OSX you can do

    alias py.test='python /path/to/checkout/bin/py.test'
    alias py.test3='python3 /path/to/checkout/bin/py.test'

to easily have the two main py.test runs available ... adding
a py.testjython alias is a bonus :)

In any case, feel free to ask more questions, also on #pylib
freenode. 

cheers,
holger