Re: [PATCH 1/2] patch: special-case quilt in debian

[Henning Schild <henning.schild@siemens.com>]

On Wed, 29 Jul 2020 17:31:34 +0200
Jan Kiszka <jan.kiszka@siemens.com> wrote:

> On 29.07.20 17:08, Henning Schild wrote:
> > Hi,
> > 
> > working on that and getting some feedback from Adriaan the whole
> > issue is harder so solve than i initially thought.
> > 
> > Having Isar and Debian use quilt is hard if not impossible to get
> > right. Here i propose to detect Debian-quilt usage and hook into it.
> > While that is a nice idea and actually does work, it has one major
> > problem. We will not be able to patch "debian/" with it, which some
> > patches might want to do.
> > 
> > Now why cant we use two quilts (in some cases):
> > 1. in addition to the "patches" dir quilt creates a dir with its
> > state, and it finds that directory on more levels than it finds
> > "patches". That actually means that the first call to quilt will
> > potentially break the other caller, because it will find the wrong
> > state dir and work on the wrong patches. We do not even know which
> > instance comes first, if we fetch with "apt://" debian comes first,
> > otherwise isar comes first. 2. isar never should come first because
> > patching before debian applies its patches means potentially
> > breaking the debian-series, isar needs to patch last ... maybe
> > unless it patches "debian/" ...
> > 
> > So i suggest to stick to what i propose with that patch and add a
> > special patching method just for "debian/" and just for the
> > "debian-uses-quilt" case. The user would have to mark the patches
> > somehow, maybe with a naming convention or a SRC_URI paramter. Now
> > we need a special patch method to apply those outside of the
> > debian-quilt universe.
> > SRC_URI+="foo.patch;apply-with-isar=1" What do you think?  
> 
> If we are to add a special flag, I would say "debian-patch". Semantic 
> would be "inject into the debian package patch queue (and,
> implicitly, "apply=no" for Isar).

I am not sure about the user interface, when patching the source we
should magically hook into debians quilt by default, because we need to
be after debian. That breaks legacy recipes that patch "debian/" ...

And "debian-patch" could also be misunderstood as patching "debian/".
Let me come up with an implementation and discuss those details later.

> > 
> > The two quilts getting into each others ways can potentially also be
> > avoided if we prepare a QUILTRC for the Isar side. In that case we
> > can maybe still use two quilts and give users an option to hook
> > individual patches into debian instead of isar. Because isar should
> > not actually patch before debian does it ... In fact if debian uses
> > quilt any change that debian did not apply itself will trigger
> > build errors, only patches to "debian/" will be ok.  
> 
> Indeed. We likely need to split patches into those that target the 
> source and those that address debian/. The former should be hooked
> into debian/, the latter could be applied the classic way.

I am afraid the "classic way" wont work, unless we manage to convince
quilt to work on S/patches and do not fall for S/debian/patches in case
of "apt://". I think it is not only "apt://" but might also affect
partial rebuilds where somehow debians quilt already ran before isars
quilt enters the stage. Let us see.

Henning

> Jan
> 
> > 
> > Henning
> > 
> > On Tue, 28 Jul 2020 22:31:52 +0200
> > Henning Schild <henning.schild@siemens.com> wrote:
> >   
> >> From: Henning Schild <henning.schild@siemens.com>
> >>
> >> The OE patch lib uses quilt and so do many debian packages as well.
> >> Those two do not work well together, it is really hard to create a
> >> patch that will apply and not break what debian does later. debian
> >> is very pedantic about unexpected changes so even if patching
> >> works, building might not.
> >>
> >> Introduce a special-case where we detect quilt usage of a debian
> >> package and hook in there. Also make sure we are on top of debian
> >> so we do not risk breaking patches we inherit from there.
> >>
> >> If anyone ever managed to create a patch that works well in the
> >> face of two quilts, that might break with this change. You can set
> >> PATCHTOOL to "quilt" in your recipe to disable the magic.
> >>
> >> Signed-off-by: Henning Schild <henning.schild@siemens.com>
> >> ---
> >>   meta/classes/patch.bbclass | 28 ++++++++++++++++++++++++++++
> >>   1 file changed, 28 insertions(+)
> >>
> >> diff --git a/meta/classes/patch.bbclass
> >> b/meta/classes/patch.bbclass index 3060755a5c..06f32a2197 100644
> >> --- a/meta/classes/patch.bbclass
> >> +++ b/meta/classes/patch.bbclass
> >> @@ -91,6 +91,28 @@ def should_apply(parm, d):
> >>   
> >>   should_apply[vardepsexclude] = "DATE SRCDATE"
> >>   
> >> +def patch_do_debian_quilt(patchdir, d):
> >> +    import oe.patch
> >> +    class DummyPatchSet(oe.patch.PatchSet):
> >> +        def Clean(self):
> >> +            True
> >> +
> >> +        def Import(self, patch, force):
> >> +            os.putenv('QUILT_PATCHES', 'debian/patches')
> >> +            # push all so we are on top of debian
> >> +            pushed = False
> >> +            if os.path.exists(os.path.join(self.dir,
> >> 'debian/patches/series')):
> >> +                oe.patch.runcmd(["quilt", "push", "-a"], self.dir)
> >> +                pushed = True
> >> +            oe.patch.runcmd(["quilt", "import", "-f",
> >> os.path.join(d.getVar('WORKDIR'),
> >> os.path.basename(patch['file']))], self.dir)
> >> +            if pushed:
> >> +                oe.patch.runcmd(["quilt", "pop", "-a"], self.dir)
> >> +
> >> +        def Push(self, force = False):
> >> +            True
> >> +
> >> +    return DummyPatchSet(patchdir, d)
> >> +
> >>   python patch_do_patch() {
> >>       import sys
> >>   
> >> @@ -118,6 +140,12 @@ python patch_do_patch() {
> >>   
> >>       s = d.getVar('S')
> >>   
> >> +    debianformat = os.path.join(s, 'debian/source/format')
> >> +    if os.path.exists(debianformat) and d.getVar('PATCHTOOL') !=
> >> 'quilt':
> >> +        with open(debianformat, 'r+') as f:
> >> +            if f.readline() == '3.0 (quilt)\n':
> >> +                cls = patch_do_debian_quilt
> >> +
> >>       os.putenv('PATH', d.getVar('PATH'))
> >>   
> >>       # We must use one TMPDIR per process so that the "patch"
> >> processes  
> >   
>