cbindgen failures after bumping Rust dependencies

[jlebon]

Still tracking this down, but it seems like I can no longer build git master from scratch after 3f722b5. It fails on the step to call cbindgen to generate the header:

$ cbindgen -c rust/cbindgen.toml -o rpmostree-rust.h ./rust -vv
ERROR: Couldn't execute `cargo metadata` with manifest "./rust/Cargo.toml": Json(Error("EOF while parsing a value", line: 1, column: 0))
ERROR: Couldn't generate bindings for ./rust.

[jlebon]

OK, so one obvious thing here is that CI is using cbindgen: internal, which currently pulls in v0.6.8, while I'm using the packaged one, which is at v0.6.3. Trying internal.

[jlebon]

Hmm nope, even internal fails:

   Compiling cbindgen v0.6.8
   Compiling rpmostree-bindgen v0.1.0 (file:///home/jlebon/Code/github.com/projectatomic/rpm-ostree/bindgen)
    Finished dev [unoptimized + debuginfo] target(s) in 1m 40s
  GEN      rpmostree-rust.h
error: Couldn't execute `cargo metadata` with manifest "./rust/Cargo.toml": Json(Error("EOF while parsing a value", line: 1, column: 0))
make: *** [Makefile:5362: rpmostree-rust.h] Error 1

[jlebon]

OK, so I think this is due to cargo v1.29.2 erroring out on fuchsia-cprng now using editions:

$ cargo metadata
warning: please specify `--format-version` flag explicitly to avoid compatibility problems
error: unable to get packages from source

Caused by:
  failed to parse manifest at `/home/jlebon/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/fuchsia-cprng-0.1.1/Cargo.toml`

Caused by:
  editions are unstable

Caused by:
  feature `edition` is required

It works fine with the latest cargo. So I think CI is just not hitting this because it's pulling in cargo from the Fedora repos, while the rust check we have doesn't actually go through the cbindgen path. Will fix.