[PATCH 1/2] doc/sphinx: Enable keep_warnings

Wed Jul 20 12:29:01 UTC 2016

Am 20.07.2016 um 13:27 schrieb Daniel Vetter <daniel.vetter at ffwll.ch>:

> On Wed, Jul 20, 2016 at 12:55 PM, Markus Heiser
> <markus.heiser at darmarit.de> wrote:
>> Hi Daniel, hi Mauro,
>> 
>> Am 19.07.2016 um 17:32 schrieb Daniel Vetter <daniel.vetter at ffwll.ch>:
>> 
>>> On Tue, Jul 19, 2016 at 5:25 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>>>> On Tue, Jul 19, 2016 at 4:59 PM, Markus Heiser
>>>> <markus.heiser at darmarit.de> wrote:
>>>>> 
>>>>> Am 19.07.2016 um 13:42 schrieb Daniel Vetter <daniel.vetter at ffwll.ch>:
>>>>> 
>>>>>> Unfortunately warnings generated after parsing in sphinx can end up
>>>>>> with entirely bogus files and line numbers as sources. Strangely for
>>>>>> outright errors this is not a problem. Trying to convert warnings to
>>>>>> errors also doesn't fix it.
>>>>>> 
>>>>>> The only way to get useful output out of sphinx to be able to root
>>>>>> cause the error seems to be enabling keep_warnings, which inserts
>>>>>> a System Message into the actual output. Not pretty at all, but I
>>>>>> don't really want to fix up core rst/sphinx code, and this gets the job
>>>>>> done meanwhile.
>>>>> 
>>>>> Hi Daniel,
>>>>> 
>>>>> may I misunderstood you. Did you really get more or different warnings
>>>>> if you include them into the output with "keep_warnings"?
>>>>> 
>>>>> The documentation says:
>>>>> 
>>>>> "Regardless of this setting, warnings are always written
>>>>>  to the standard error stream when sphinx-build is run."
>>>>> 
>>>>> see http://www.sphinx-doc.org/en/stable/config.html#confval-keep_warnings
>>>>> 
>>>>> Or did you not run "make cleandoc" first? Sphinx caches the doctrees
>>>>> and reports markup errors only when you rebuild the cache.
>>>>> The cache is also rebuild if you touch one of the source, e.g.
>>>>> the drivers/gpu/drm/drm_crtc.c or the rst-file where the drm_crtc.c
>>>>> is referred by a kernel-doc directive .. these dependence sometimes
>>>>> confuse me .. when I missed log messages, I clean the cache e.g. by
>>>>> target cleandocs.
>>>> 
>>>> Yes I'm aware that sphinx it's WARNINGs when doing a partially
>>>> rebuild, this is something entirely different. I didn't get more or
>>>> less warnings this way, but keep_warning = True seems to be the only
>>>> way to get reasonable information about them. Without that I get
>>>> warnings (for included kernel-doc) where the source file is the .rst
>>>> file that pulls in the kernel doc, and the line number is entirely
>>>> bogus (often past the end of the containing .rst).
>>>> 
>>>> With this I can at least then open the generated .html file, search
>>>> for the System Message and figure out (by looking at the surrounding
>>>> context) where the error really is from.
>>>> 
>>>> Strangely this only happens for WARNING. If I manged the kerneldoc
>>>> enough to upset sphinx into generating an ERROR, the line numbers and
>>>> source files are correct.
>>>> 
>>>> See patch 2/2 in this series for examples of such WARNINGs: Mostly
>>>> it's unbalanced _ * or `` annotations that confuse sphinx/rst a bit.
>>>> If you want to play around with the gpu sphinx conversion to reproduce
>>>> these locall you can grab the drm-intel-nightly branch from
>>>> 
>>>> https://cgit.freedesktop.org/drm-intel
>>>> 
>>>> It already includes Jon's latest docs-next branch.
>>> 
>>> btw, I couldn't check this since I didn't figure out how to intercept
>>> the parsed rst tree and view it, but I think what's going on is:
>>> - The source file for these warnings is .rst file containing the
>>> kernel-doc directive. This seems to be a bug in sphinx/docutils since
>>> we never use that file name when appending files at all.
>>> - The line number looks like it's just counting the inserted
>>> kernel-doc lines as part of the containing .rst file. At least
>>> changing the content_offset in nested_parse seems to suggest that this
>>> is the start line (e.g. adding 10k there results in all bogus WARNING
>>> line numbers being increased by 10k). And adding more blank lines at
>>> the beginning of the inserted kernel-doc rst also increases the
>>> reported lines. But not when inserting blank lines at the end (i.e. it
>>> seems like it's being reset after each directive again).
>> 
>> Thanks for the explanation.
>> 
>>> All that suggest to me this is a sphinx-internal issue, and google
>>> sugggests there's lots of errata around line reporting. Hence why I
>>> went with this. But of course a proper fix would be awesome! Just a
>>> bit outside of what I think I can pull off ...
>> 
>> It is not really a sphinx-internal issue (rather a drawback of the design).
>> The state machine needs a system reporter that takes the origin file
>> and it's line numbers as context.
>> 
>> I send a fix to Jon:
>> 
>> http://mid.gmane.org/1469011138-12448-1-git-send-email-markus.heiser@darmarit.de
>> 
>> could you test this patch and send us some feedback / thanks.
> 
> Yup, seems to work nicely. Thanks a lot for fixing this. Jon, pls
> drop/revert my hack and take Markus' proper fix instead.
> 
>> One remark: The line numbers are not "perfect". This is due to the fact,
>> that the kernel-doc parser could not generate "perfect" line numbers
>> or all extracted doc-items .. daniel knows this ;)
>> 
>> If you did not find the cause of a warning in the line number given
>> by the warning, take a look one line or one block above and/or below,
>> mostly you will see the cause.
> 
> Hm, I think I still have a few off-by-one in the kernel-doc line
> numbers. But tbh with all the intermediate layers I wasn't sure which
> one is wrong and where it would need to be fixed up. But it seems like
> for a bunch of cases kernel-doc reports 1 line too much.
> 
> If someone with more insight into all this would try to improve this,
> I think it'd be awesome ;-)

It will never be "perfect" ... as far as I know, Sphinx (docutils) will
always report on the block level, not on line level of the rst-origin.

The off-by-on could be fixed, I plan to revise the kernel-doc perl script, when
we know, what we need for man-pages [1], but I will wait for Jon's and Jani's
thoughts about man pages first.  

[1] http://mid.gmane.org/2CE565E6-19D4-4835-9A32-2FCAE754B357@darmarit.de

-- Markus --

> 
> Cheers, Daniel
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch