How to reuse code from the main bin in another bin?

Question

My project structure looks like this:

.
├── Cargo.lock
├── Cargo.toml
└── src
    ├── bin
    │   └── other.rs
    ├── main.rs
    └── util.rs

(code: https://gitlab.com/msrd0/cargo-bin-import)

In my other.rs, I'm trying to reuse code from the util mod, which is declared as a public mod in my main.rs file. I tried the following:

• use util::do_sth
• use crate::util::do_sth
• use cargo_bin_import::util::do_sth (with and without extern crate)
• mod util; use util::do_sth
• extern crate util; use util::do_sth (suggested by rustc)

None of the above worked and gave me error messages similar to this one:

error[E0432]: unresolved import `crate::util`
 --> src/bin/other.rs:1:12
  |
1 | use crate::util::do_sth;
  |            ^^^^ maybe a missing `extern crate util;`?

error: aborting due to previous error

Answer 1

Use a library and two binaries, then reuse the lib's code in the two binaries. Example:

Cargo.toml

[lib]
name = "utils"
path = "src/utils.rs"

# cargo build --bin other
[[bin]]
name = "other"
path = "src/bin/other.rs"

# cargo build --bin main
[[bin]]
name = "main"
path = "src/main.rs"

Then use utils::{...}. The path are taken from your question, but putting main inside bin/ and renaming utils.rs to lib.rs could be a more standard way to do it.

If the library is generic enough, you could even release it on crates.io for others to benefit from it.