[PATCH 1 of 8 py3] bundle2: raise a more helpful error if building a bundle part header fails

[Yuya Nishihara]

On Sat, 16 Sep 2017 11:08:07 -0400, Augie Fackler wrote:
> 
> > On Sep 16, 2017, at 7:54 AM, Yuya Nishihara <yuya at tcha.org> wrote:
> > 
> > On Fri, 15 Sep 2017 19:14:04 -0400, Augie Fackler wrote:
> >> # HG changeset patch
> >> # User Augie Fackler <raf at durin42.com>
> >> # Date 1505515049 14400
> >> #      Fri Sep 15 18:37:29 2017 -0400
> >> # Node ID 662bbd6d96952985eff807f424dd128663724672
> >> # Parent  209120041d12b524648fa856732aa404dfedd91d
> >> bundle2: raise a more helpful error if building a bundle part header fails
> >> 
> >> I've tripped on this several times now, and am tired of debugging. Now
> >> the header parts are part of the error message when the ''.join()
> >> fails, which makes debugging obvious.
> >> 
> >> diff --git a/mercurial/bundle2.py b/mercurial/bundle2.py
> >> --- a/mercurial/bundle2.py
> >> +++ b/mercurial/bundle2.py
> >> @@ -1050,7 +1050,11 @@ class bundlepart(object):
> >>             header.append(key)
> >>             header.append(value)
> >>         ## finalize header
> >> -        headerchunk = ''.join(header)
> >> +        try:
> >> +            headerchunk = ''.join(header)
> >> +        except TypeError:
> >> +            raise TypeError(u'Found a non-bytes trying to '
> >> +                            u'build bundle part header: %r' % header)
> > 
> > I was making it a r'' string, but probably ProgrammingError would be better.
> 
> I was conflicted on this one. Preserving the type of the exception seemed reasonable, since this can only happen with weird bugs, but it’s also something I can just sit on for a while as a debugging aid.

Okay, queued with s/u'/r'/ change in flight, thanks.