RFE: %generate_buildrequires should re-run until all dependencies are satisfied

[hroncok]

rpm-software-management/rpm#755

%generate_buildrequires currently only runs once. it should loop until no new depndencies are needed.

To reproduce:

%generate_buildrequires
echo package1
if rpm -q package1 &>/dev/null; then echo package2; fi

Actual result:

Executing(%generate_buildrequires):
+ umask 022
+ cd /builddir/build/BUILD
+ echo package1
+ rpm -q package1
+ RPM_EC=0
BUILDSTDERR: ++ jobs -p
+ exit 0
package1
Wrote: /builddir/build/SRPMS/reproducer_dynbrs-0.0-1.fc31.buildreqs.nosrc.rpm
Child return code was: 11

(installs package1)

Executing(%generate_buildrequires):
+ umask 022
+ cd /builddir/build/BUILD
+ echo package1
+ rpm -q package1
+ echo package2
+ RPM_EC=0
BUILDSTDERR: ++ jobs -p
+ exit 0
package1
package2
Executing(%build):
...

Expected results:

Executing(%generate_buildrequires):
+ umask 022
+ cd /builddir/build/BUILD
+ echo package1
+ rpm -q package1
+ RPM_EC=0
BUILDSTDERR: ++ jobs -p
+ exit 0
package1
Wrote: /builddir/build/SRPMS/reproducer_dynbrs-0.0-1.fc31.buildreqs.nosrc.rpm
Child return code was: 11

(installs package1)

Executing(%generate_buildrequires):
+ umask 022
+ cd /builddir/build/BUILD
+ echo package1
+ rpm -q package1
+ echo package2
+ RPM_EC=0
BUILDSTDERR: ++ jobs -p
+ exit 0
package1
package2
Wrote: /builddir/build/SRPMS/reproducer_dynbrs-0.0-1.fc31.buildreqs.nosrc.rpm
Child return code was: 11

(installs package2)

Executing(%generate_buildrequires):
+ umask 022
+ cd /builddir/build/BUILD
+ echo package1
+ rpm -q package1
+ echo package2
+ RPM_EC=0
BUILDSTDERR: ++ jobs -p
+ exit 0
package1
package2
Executing(%build):
...

[hroncok]

See https://github.com/rpm-software-management/mock/blob/devel/mock/py/mockbuild/backend.py#L722-L725

[praiskup]

Well, we discussed this in original feature request
rpm-software-management/rpm#104 (comment),
but we didn't really found a real use-case to bother with calculating fixed
point. What is your real use-case?

[hroncok]

My real use case is Python's two phased dependency resolution in PEP 517.

1. First, dependencies and build backend are parsed from the pyproject.toml file.
2. Second, a hook is called on the build backend to get the depndencies.

It could look like this:

1. parse toml, get depndneices: flit, build backend: flit
2. call flit.get_deps(), get: cython

Surely, without flit, we cannot get the information about cython. in order to make this work, we need to run the dependency check twice.

[praiskup]

TBH I'm not familiar with that PEP; though it sounds like you don't need to iterate -- but (at most) two steps. Can flit be added to static build requires?

[hroncok]

Yes, we need just two.

yes, flit can be added to static BRs to workaround this problem. It is not always flit, there are multiple backends (setuptools, flit, poetry...).

[xsuchy]

My main point is that I do not want to have - even potential - infinite loop. And detecting that installSrpmDeps do nothing is hard.
OK. Let's do more loops. Ten loops should be enough for everybody (I am sure this will be quoted with laughter one day).

[praiskup]

constant? => config option :-)

[hroncok]

will it do 10 loops by default or only if some packages are missing?

[xsuchy]

will it do 10 loops by default or only if some packages are missing?

only if some packages are missing. The constant is the upper limit.

[hroncok]

Awesome!

[hroncok]

only if some packages are missing. The constant is the upper limit.

with af02efc this is not true - not only it loops even when no new buildrequires are added, but it also does not stop after 10 runs.

[hroncok]

#285

[xsuchy]

Nice catch - thank you.