I am starting out with a Bazel project in Rust, without Cargo. I am trying to set up a feature-gated, optional dependency.

I have a crates_vendor set up:

crates_vendor(
    name = "crates_io",
    cargo_lockfile = ":Cargo.Bazel.lock",
    mode = "remote",
    packages = {
        "tonic": crate.spec(version = "*"),
        "serde": crate.spec(version = "1.0"),
        "serde_json": crate.spec(version = "1.0"),
    },
    repository_name = "crates_io",
    tags = ["manual"],
)

Now my Rust library is defined as:

rust_library(
    name = "foo",
    srcs = glob("**/*.rs"),
    deps = [
        "@crates_io//:serde",
        "@crates_io//:serde_json",
    ],
)

It is @crates_io//:serde_json that I want to feature-gate.

The Cargo.toml code for that would be:

[dependencies]
serde_json = { version = "1.0", optional = true }

[features]
json = ["dep:serde_json"]

However, as I mentioned, this is a non-Cargo project.

What would be the correct way of achieving this? Tried diggint through the docs, but can’t figure out.