cargo_toml_env_vars requires extra Bazel repository dependencies when building generated targets

[jayzhuang]

Version: 0.59.0
Relevant PR: #2772

I'm using WORKSPACE with rules_rust_dependencies only, and I'm getting the following errors:

ERROR: no such package '@@rules_rust_ctve__cargo-util-schemas-0.3.1//': The repository '@@rules_rust_ctve__cargo-util-schemas-0.3.1' could not be resolved: Repository '@@rules_rust_ctve__cargo-util-schemas-0.3.1' is not defined

I think this is because ctve_crate_reposotires is not in rules_rust_dependencies. For my use case I have locally vendored third-party crates and I check in generated BUILD.bazel files. When building with Bazel later, it doesn't need to know about crate_universe since it's simply consuming generated targets. However, with the addition of cargo_toml_env_vars, it looks like I need to make sure crate_universe_dependencies is called in WORKSPACE as well, which in turn pulls in way too many dependencies than we want to vendor.

@illicitonion I guess a simple workaround for my use case would be a knob to disable generation of cargo_toml_env_vars targets. Is that a reasonable thing to do?

[UebelAndre]

I think this might be resolved by #3337

[jayzhuang]

Not really, I'm still seeing the same error after cherry-picking your commit.

I think these dependencies are needed as soon as Bazel tries to build a cargo_toml_env_vars? For example one of my generated BUILD.bazel has something like:

cargo_toml_env_vars(
    name = "cargo_toml_env_vars",
    src = "Cargo.toml",
)

rust_library(
    name = "aho_corasick",
    ....
    rustc_env_files = [
        ":cargo_toml_env_vars",
    ],
    ...
)

[illicitonion]

Sorry for the breakage here!

Yeah, my expectation is that if you're using anything in @rules_rust//crate_universe you're calling crate_universe_dependencies() as documented in https://bazelbuild.github.io/rules_rust/crate_universe.html - I'm honestly pretty surprised that vendor works without these, but I guess we pull in prebuilds for most of the stuff...

But good news! There's already a knob to disable cargo_toml_env_vars generation - see

rules_rust/cargo/cargo_toml_variable_extractor/3rdparty/BUILD.bazel

Line 13 in da170ec

render_config = render_config(generate_cargo_toml_env_vars = False),

for an example :)

However, it would be good to get you into a place where you can opt in to just loading the dependencies you need for this without pulling in everything needed for building cargo-bazel. Perhaps we can filter more things out if bootstrap is false?

[jayzhuang]

Thanks @illicitonion, that's exactly what I want! And appreciate your change since that's something we might want one day.

Our set up is bit complicated, we have multiple Bazel workspaces. We run crates_vendor in a dedicated workspace only to generate BUILD.bazel files. In this dedicated workspace we have crate_universe_dependencies. In the Bazel workspaces where we consume the generated BUILD.bazel files to build other things, we only provide rules_rust_dependencies.

Again, thanks for your help, closing.