#726 breaks build

[matze]

We have a build.rs to add some additional methods to services. Upgrading from 0.11.1 to 0.11.2 caused this (actual binary names and paths redacted)

error: failed to run custom build command for `…`

Caused by:
  process didn't exit successfully: `/…/build-script-build` (exit status: 101)
  --- stderr
  thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', /…/prost/prost-build/src/lib.rs:1069:52
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

I could pinpoint the regressing behaviour to the change commited with #726 however I do not see yet how this causes the unwrap to fail. The crash traces from

    prost_build::Config::new()
        .file_descriptor_set_path(desc_path.clone())
        .skip_protoc_run()
        .extern_path(".foo", "foo_proto")
        .include_file("prost_includes.rs")
        .service_generator(Box::new(gen))
        .compile_protos(&Vec::<&str>::default(), &Vec::<&str>::default())?;

in build.rs to

        if let Some(ref mut service_generator) = self.service_generator {
            for (module, package) in packages {
                let buf = modules.get_mut(&module).unwrap();
                service_generator.finalize_package(&package, buf);
            }
        }

in the prost-build/src/lib.rs.

[LucioFranco]

Would it be possible to provide a reproduction proto file I can play around with?

[matze]

I will try to come up with a repro build.rs and proto file(s).

[LucioFranco]

I just need the proto file really, I can create a test to reproduce and look at it. We may need to yank 0.11.2 then and either fix or remove this commit. Thanks!

[matze]

Hmm, it's not so easy to come up with a repro from scratch, it will take a while I guess :-(

[LucioFranco]

All good! This has been a really tricky feature that I already had to revert once so getting that edge case test case would be super valuable!

[matze]

I could pin it down. As written in the PR, it happens for protos that specify a parent package.

[matze]

@LucioFranco could you reproduce this issue?

[LucioFranco]

I have not had the time to try it out yet but I think for your PR adding a test would be very helpful.

[matze]

The issue is actually a combination of the mentioned path hierarchy as well as the fact that we skip generating one particular service causing the output to be empty and hence the module to be removed. So, I will close this issue as a very peculiar case.