The `binding.rs` that is resolved in the upstream crate still causes failure in the downstream crate

[xmh0511]

Crate name

tun-rs

Build failure link

https://docs.rs/crate/tun-rs/2.5.5/builds/2364143/x86_64-apple-darwin.txt

Additional details

The upstream crate route_manager has adopted the following way to resolve the failure of building on doc.rs

#![allow(warnings)]
#[cfg(not(docsrs))]
include!(concat!(env!("OUT_DIR"), "/bindings.rs"));

#[cfg(all(target_os = "freebsd", docsrs))]
include!("freebsd_bindings.rs");

#[cfg(all(target_os = "openbsd", docsrs))]
include!("openbsd_bindings.rs");

#[cfg(all(target_os = "macos", docsrs))]
include!("macos_bindings.rs");

It does work for route_manager itself, see https://docs.rs/crate/route_manager/0.2.3/builds/2364099/x86_64-apple-darwin.txt. However, the downstream crate tun-rs uses the route_manager; it still has a failure when building on doc.rs

[INFO] [stderr] error: couldn't read `/opt/rustwide/target/x86_64-apple-darwin/debug/build/route_manager-0a8d6cd0a193af04/out/bindings.rs`: No such file or directory (os error 2)
[INFO] [stderr]  --> /opt/rustwide/cargo-home/registry/src/index.crates.io-1949cf8c6b5b557f/route_manager-0.2.3/src/unix_bsd/bind.rs:3:1
[INFO] [stderr]   |
[INFO] [stderr] 3 | include!(concat!(env!("OUT_DIR"), "/bindings.rs"));
[INFO] [stderr]   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[INFO] [stderr] 

It looks like tun-rs don't pass docsrs to route_manager such that #[cfg(doscrs)] can work on the side of route_manager when building docs for tun-rs,

[syphar]

Hi,

from what I know, #[cfg(doscrs)] is only passed to the crate that is documented at the moment, not its dependencies.

So in this case, the upstream crate would have to be changed so it uses (for example) a normal cargo feature to enable the docs-specific config. Then your upstream create can use docs.rs metadata to enable the feature for their docs builds.

In your crate you now can do the same, and enable that special feature of the upstream dependency in your own docs.rs metadata.

[xmh0511]

Adding

[package.metadata.docs.rs]
rustc-args = ["--cfg","docsrs"]

in the Cargo.toml can make #[cfg(not(docsrs))] work in the upstream crate when building on docs.rs. But, I don't know why RUSTFLAGS="--cfg docsrs" is needed when building documents.