[Qgis-developer] How to debug and unit test Python plugins outside QGIS (e.g. in Ecplise IDE + PyDev)

[Alex Mandel]

I tried Eclipse with Pydev years back and felt that it was a dead end
for Python programming (Also a bit of a resource hog). Partly because
all the useful stuff wasn't in the open source version, and partly
because Eclipse was a huge memory hole for something as simple as python.

Eric, SPE, and Spyder all seem like better options - 2 of the 3 are
written with PyQt also and I've gotten at least 2 of them to work with
OSGeo4W installs (Requires launching via a batch file).

I'm not so sure this would be a QGIS SOC project, however if it's just a
task in say creating unit tests that would make sense.

Thanks,
Alex

On 03/03/2011 12:26 AM, Stefan Keller wrote:
> I still hope this should be an issue to be solved within reasonable
> time given Eclipse as IDE.
> However, yes, it could be that this turns out to be a larger endeavour.
> I can imagine that one solution could be that Python stubs have to be
> generated out of PyGt4/QGIS libs?
> 
> Yours, S.
> 
> 2011/3/3 Andreas Neumann <a.neumann at carto.net>:
>> Couldn't this be a GSoC idea?
>>
>> Creating a developer-friendly Development environment for Python Developers?
>> With a nice debugging solution, code completion, possibility to do unit
>> tests, integration with the plugin repository, etc.?
>>
>> I would guess a lot of devs would gain productivity through such improved
>> developer tools and a student could learn quite a bit in putting these
>> together.
>>
>> Andreas
>>
>> On Thu, 3 Mar 2011 08:38:36 +0100, Stefan Keller wrote:
>>>
>>> Many thanks also for the hint to standalone apps.!
>>> I still hope there is a solution to unit test QGIS plugins.
>>> This would make QGIS programmers even more happy :->
>>>
>>> Yours, S.
>>>
>>>
>>> 2011/3/3 Alex Mandel <tech_dev at wildintellect.com>:
>>>>
>>>> It might be possible, I'm not super familiar with units tests yet.
>>>> The big issue I see is that most plugins rely on the main QGIS app
>>>> providing data to the plugin or interacting with the plugin. If you can
>>>> design the test to provide what the unit test needs then it should be
>>>> doable. After all you can build standalone python apps with the QGIS api.
>>>>
>>>> Thanks,
>>>> Alex
>>>>
>>>> On 03/02/2011 10:13 PM, Stefan Keller wrote:
>>>>>
>>>>> Hi Alex,
>>>>>
>>>>> Many thanks for your reply. I'll try this.
>>>>>
>>>>> But: So you say implicitly that its impossible to run unit tests
>>>>> (PyUnit) on QGIS plugins?
>>>>> I still hope there is a way to make PyGt4 module interface accessible
>>>>> outside QGIS. At runtime its there, so it should be somehow possible
>>>>> either by "Forced builtin libs" or by extracting the information by
>>>>> hand with dummy stubs...?
>>>>>
>>>>> Yours, S.
>>>>>
>>>>> 2011/3/3 Alex Mandel <tech_dev at wildintellect.com>:
>>>>>>
>>>>>> On 03/02/2011 03:57 PM, Stefan Keller wrote:
>>>>>>>
>>>>>>> Hi,
>>>>>>>
>>>>>>> I'm new to writing Python plugins for QGIS and I like to debug and
>>>>>>> unit test theses outside QGIS runtime but don't see any instructions
>>>>>>> on how to do this.
>>>>>>>
>>>>>>> Of course, the ultimate test of any plugin is to run it inside QGIS.
>>>>>>> But I'd like do that outside QGIS for example in Eclipse IDE (+ PyDev)
>>>>>>> in order to get code-completion, to debug it and to write unit tests
>>>>>>> on it.
>>>>>>>
>>>>>>> The problem is that one gets "ImportError: No module named ..." with
>>>>>>> mostly PyQt4/qgis modules which (of course) cannot be imported.
>>>>>>>
>>>>>>> This post mentions "Forced builtin libs" and reports a similar
>>>>>>> problem:
>>>>>>> http://www.osgeo.org/pipermail/qgis-developer/2010-February/009182.html
>>>>>>> ... and this PyDev documentation explains "Forced builtin libs" and
>>>>>>> "Predefined completions":
>>>>>>> http://pydev.org/manual_101_interpreter.html#id1
>>>>>>>
>>>>>>> I can't imagine that I'm the first trying to debug and unit test
>>>>>>> Python plugins for QGIS.
>>>>>>>
>>>>>>> Can anybody give me a hand on this?
>>>>>>>
>>>>>>> Yours, S.
>>>>>>
>>>>>> I've been meaning to write this up for some time. The only way I've
>>>>>> found to Debug a QGIS plugin is using a debugger hook in python. While
>>>>>> I
>>>>>> have only tested this method with SPE's Winpdb (No Win does not stand
>>>>>> for MS Windows - SPE is python cross platform) debugger it
>>>>>> theoretically
>>>>>> should be possible with other tools if they support the same kind of
>>>>>> debugging method.
>>>>>>
>>>>>> Basically I insert something like:
>>>>>> import rpdb2; rpdb2.start_embedded_debugger("testing")
>>>>>>
>>>>>> just below the main part of my plugin:
>>>>>> class MetaEditPlugin:
>>>>>>    def __init__(self,iface):
>>>>>>        #Only turn on to use winpdb debugger
>>>>>>        import rpdb2; rpdb2.start_embedded_debugger("testing")
>>>>>>
>>>>>> Then the procedure is to start QGIS, Launch the plugin, switch to SPE's
>>>>>> winpdb, then do File attach, put in the same password "testing".
>>>>>> It will then show you the running apps you can connect to, once you
>>>>>> select and connect the plugin will continue to run.
>>>>>> At this point you can set breakpoints and catch errors. If/When it
>>>>>> stops
>>>>>> at such a point you can interact with the app in a way similar to
>>>>>> Python's pdb sending eval and exec snippets, and inpecting all your
>>>>>> variables in the list.
>>>>>>
>>>>>> Make sure to comment out that line for production use otherwise your
>>>>>> plugin will always stall and wait for the debug to connect.
>>>>>>
>>>>>> Basically I think this falls under the term "Remote Debugging" if you
>>>>>> want to try and find ways to do it with other apps.
>>>>>>
>>>>>> I'm not sure there is any other practical method as most plugins rely
>>>>>> on
>>>>>> the QGIS built in stuff to be in an active session, so I wouldn't waste
>>>>>> too much time trying to do it without QGIS running at all.
>>>>>>
>>>>>> Enjoy,
>>>>>> Alex