Cannot include generated code

[xitep]

Hi,

following cargo's documentation I've tried to generate my protobufs at build time (through a build.rs script) and include them in my main.rs using:

...
mod model {
    include!(concat!(env!("OUT_DIR"), "/model.rs"));
}
...

However, the (rustc) compilation then fails with:

.../target/debug/build/pubmonitor-42b07ea6e237e2f6/out/model.rs:3:3: 3:4 error: an inner attribute is not permitted in this context
.../target/debug/build/pubmonitor-42b07ea6e237e2f6/out/model.rs:3 #![allow(dead_code)]
                                                                    ^
.../target/debug/build/pubmonitor-42b07ea6e237e2f6/out/model.rs:3:3: 3:4 help: place inner attribute at the top of the module or block
...

It seems that module level attributes (e.g. #![allow(dead_code)] here) are not allowed in included content. Would there be a way to avoid these in the generated code by turning them into item-level attributes where needed?

Many thanks,
P.

[stepancheg]

Why can't you just copy model.rs into source directory, and then include generated file as mod model; as regular source file?

[xitep]

Well, that's what I'm doing right now. But it feels rather like a workaround to me.

[WillDignazio]

I've gotten around this by using a build.rs script that generates the source before the build process, then cargo will pick it up if you include it in a mod.rs. It's a little clunky, but not far off from what other large projects do.

[stepancheg]

I think rust-protobuf does it properly. But if you need to include generated code in another file, I might suggest stripping module attributes with sed scripts.

[xitep]

ok with me, i think that's feasible.

[mpartel]

FWIW another dirty workaround is to modify the generated file in your build.rs to add a mod foo { ... } around it. Then it can be included from a file under src and doesn't need to be copied there. I think this is a bit better than removing the attributes, which results in build warnings.

[SirVer]

Here is an example of @mpartel idea to wrap the generated proto in mod proto { ... } inside the build.rs script and how it is then included in lib.rs. We do all of this to avoid checking in the proto.rs file into source control, instead regenerating it whenever it changes.

@stepancheg It would be really nice if this could be supported more natively. Prost does this really well with prost-build.

[aep]

@SirVer Prost looks unmaintained. Should we somehow standardize that workaround in a crate?

[stepancheg]

@SirVer @aep I think this thing can be implemented as part of rust-protobuf codegen.

If you have specific proposal, e. g.

• option (wrap_in_module)
• option to push macros to declarations from the top level

please share.

[aep]

i think it should just be a simple option to protoc_rust::run. And some docs on that would be helpful, since the default is rather surprising.

[stepancheg]

@aep option to do what exactly?

Not sure why the default is surprising. Could you explain please?

[aep]

the wrap_in_module option sounds good to me :)

well it's quite standard to put generated files into OUT_DIR, and the solution for those errors is non-obvious.
so it might help to include that in README.md

[SirVer]

@aep Rust Tower seems to be betting on Prost, so I guess development will pick up eventually again. https://medium.com/@carllerche/announcing-tower-a-library-for-writing-robust-network-services-with-rust-67273f052c40

[clintfred]

I spent a good chunk of the day figuring this out since docs.rs no longer allows files to be written outside of $OUT_DIR. I eventually went with @SirVer's workaround. https://github.com/googlecartographer/point_cloud_viewer/blob/440d875f12e32dff6107233f24b5a02cf28776dc/point_viewer_proto_rust/build.rs#L33

@stepancheg I would ask that you reconsider you stance of writing files to the src/ directory as the official solution as writing to src/ will block any crates using rust-protobuf from having documentation on docs.rs.
Or maybe there is a more official solution now and I failed to find it? If that's the case, please point me in the right direction.