Re: errorformat/cexpr bug?

On 19 February 2014, Aaron Bohannon <aaron678@gmail.com> wrote:
> Over the years, I have wasted many hours of my life on trying to write
> errorformat patterns -- and many times having to give up in defeat.
> Now, finally, I've managed to trace down a behavior that could explain
> all those hours of frustration.
>
> The meaning of the errorformat option is so arcane, though, that
> I cannot know for sure whether this is actually a bug in the
> implementation or simply the intended behavior. If it's intentional,
> can someone *please* explain to me why it works like this?
>
> :echo string(&efm)
>
> '%+CXXX,%+EERROR,%+IINFO,%-GYYY'
>
> :cgetexpr ['INFO', 'ERROR', 'XXX']
> :echomsg string(getqflist()[0].text) string(getqflist()[1].text)
>
> 'INFO' 'ERROR^@XXX'
>
> :cgetexpr ['INFO', 'YYY', 'ERROR', 'XXX']
> :echomsg string(getqflist()[0].text) string(getqflist()[1].text)
>
> 'INFO' 'ERROR'

Yeah, this one looks like a bug. What seems o be going on here is
that 'YYY' matches '%-GYYY', which sets the multiignore flag, which
doesn't get reset until 'XXX' is seen. Which basically means 'XXX' is
matched as '%-CXXX', thus ignored.

> :cgetexpr ['INFO', 'YYY', 'ZZZ', 'ERROR', 'XXX']
> :echomsg string(getqflist()[0].text) string(getqflist()[1].text) string(getqflist()[2].text)
>
> 'INFO' 'ZZZ' 'ERROR^@XXX'

In this case multiignore gets set at 'YYY', but then gets reset
when 'ZZZ' is seen. Thus the subsequent 'XXX' is correctly matched as
'%+CXXX'.

The patch below seems to fix the problem for this particular case,
but the context is pretty involved. F.i. what about O/P/Q? It would be
a good idea to have more pairs of eyes look at it.

/lcd


diff -r 7ea91c82839f src/quickfix.c
--- a/src/quickfix.c Sat Feb 15 19:47:51 2014 +0100
+++ b/src/quickfix.c Thu Feb 20 14:52:05 2014 +0200
@@ -751,7 +751,10 @@
fmt_start = fmt_ptr;

if (vim_strchr((char_u *)"AEWI", idx) != NULL)
+ {
multiline = TRUE; /* start of a multi-line message */
+ multiignore = FALSE; /* reset continuation */
+ }
else if (vim_strchr((char_u *)"CZ", idx) != NULL)
{ /* continuation of multi-line msg */
if (qfprev == NULL)

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