Build example as lib and bin at the same time

[pronebird]

Hi,

I wonder if it's possible to build an example as a lib and binary at the same time. The reason for that is basically the fact that I have a windows only crate with windows only example.

Adding #![cfg(windows)] at the top of the source code works well for libraries, but fails to compile for binaries that need explicit main.

One of solutions is to wrap everything in example.rs into mod and guard it with proper #[cfg(windows)] however it leads to issues with external crates used in the example since dev deps are defined for windows only too [target.'cfg(windows)'.dev-dependencies]. So there is a lot of noise in the code if I take this approach.

The other approach is split the source code on two targets (lib + binary):

// lib.rs
#![cfg(windows)]
#[macro_use]
extern crate log;

pub fn run() {
  // the rest of code.
}

// main.rs
#[cfg(windows)]
extern crate mylib;

#[cfg(windows)]
fn main() {
    mylib::run();
}

#[cfg(not(windows))]
fn main() {
    panic!("This program is only intended to run on Windows.");
}

So I configured the example in my Cargo.toml to include two crate-types, however Cargo does not seem to understand that configuration. At least what I see during compilation is an error that the compiler can't find mylib crate.

[[example]]
name = "example"
crate-type = ["lib", "bin"]

[ehuss]

See #3138 for a similar request (platform-specific examples).

[azriel91]

Different use case, but similar symptom: I'd like to create examples that can be run both natively and as a WASM application. The WASM version requires the example to be built as a library, whereas natively it should be a binary.

Currently I've gone with just making the example a normal crate, and users have to enter the directory (or pass in the manifest path) to run it.

[dclong]

Similar situation here.

[epage]

For myself, I feel like #9208 is the right way to be going such that I'm going to propose to the cargo team that we close this in favor of that.

[weihanglo]

Second. Closing in favor of #9208.