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

[Markus Heiser]

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.

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.

-- Markus --


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