Erroneous aliases for async-global-executor-1.4.2

[nikclayton-dfinity]

Repro:

Add a dependency on the crate async-global-executor-1.4.2 (https://github.com/async-rs/async-global-executor/blob/master/Cargo.toml).

That has this section in the Cargo.toml file:

[features]
default = ["async-io"]
tokio02 = ["tokio02-crate"]
tokio03 = ["tokio03-crate"]

# ...

[dependencies.tokio02-crate]
package = "tokio"
version = "^0.2"
optional = true
default-features = false
features = ["rt-core"]

[dependencies.tokio03-crate]
package = "tokio"
version = "^0.3"
optional = true
default-features = false
features = ["rt"]

However, the file generated by cargo raze (v0.6.1, installed a few moments ago) looks like:

# boilerplate omitted

# buildifier: leave-alone
rust_library(
    name = "async_global_executor",
    crate_type = "lib",
    deps = [
        "@raze__async_executor__1_3_0//:async_executor",
        "@raze__async_io__1_1_10//:async_io",
        "@raze__futures_lite__1_11_2//:futures_lite",
        "@raze__num_cpus__1_13_0//:num_cpus",
        "@raze__once_cell__1_4_1//:once_cell",
        "@raze__tokio__0_2_22//:tokio",
    ],
    srcs = glob(["**/*.rs"]),
    crate_root = "src/lib.rs",
    edition = "2018",
    rustc_flags = [
        "--cap-lints=allow",
    ],
    version = "1.4.2",
    tags = [
        "cargo-raze",
        "manual",
    ],
    crate_features = [
        "async-io",
        "default",
        "tokio02",
        "tokio02-crate",
    ],
    aliases = {
        "@raze__tokio__0_2_22//:tokio": "tokio03_crate",
    },
)

Note the aliases section at the bottom, and how tokio_0_2_22 points to tokio03_crate, resulting in the following build error:

INFO: From Compiling Rust lib async_global_executor v1.4.2 (1 files):
error[E0433]: failed to resolve: use of undeclared type or module `tokio02_crate`
  --> external/raze__async_global_executor__1_4_2/src/lib.rs:69:22
   |
69 | static TOKIO02: Lazy<tokio02_crate::runtime::Handle> = Lazy::new(|| {
   |                      ^^^^^^^^^^^^^ use of undeclared type or module `tokio02_crate`

error[E0433]: failed to resolve: use of undeclared type or module `tokio02_crate`
  --> external/raze__async_global_executor__1_4_2/src/lib.rs:70:42
   |
70 |     let mut rt = tokio02_crate::runtime::Builder::new()
   |                                          ^^^^^^^ not found in `tokio02_crate::runtime`

Changing that tokio03_crate to tokio02_crate is enough for the build to succeed.

[GregBowyer]

I think I have honed in on this one and should have a fix shortly, the downside is it relates to #187 and will be a bit of a rework

[joell]

When using Tokio 1.0, this aliasing bug now also triggers on async-compression 0.3.7, a dependency of reqwest 0.11.0 which itself is a fairly popular library. As more and more libraries migrate to Tokio 1.0, I expect this issue will start cropping up for people with increasing frequency.

No doubt the completion and merging of #282 would bring great rejoicing! 😄

In the meantime, an ugly hack to work around this is to use raze crate settings to skip and immediately re-add the Tokio dependency, e.g.:

[package.metadata.raze.crates.async-compression.'*']
skipped_deps    = ["tokio-1.0.1"]
additional_deps = ["@raze__tokio__1_0_1//:tokio"]

This seems to trigger cargo-raze to elide the aliases on the tokio package, which allows compilation to continue in my particular case.