cargo install uses my project's .cargo/config target triple and it shouldn't?

[slimsag]

TL;DR: I spent multiple hours trying to figure out why I couldn't cargo install some tools. It turned out that the reason I couldn't was because, unbeknownst to me, cargo install was trying to build the tools for the wrong target due to .cargo/config in my project directory!

Full explanation

1. My project has a .cargo/config file to build for a wasm target triple since my project is wasm only:

[build]
target = "wasm32-unknown-emscripten"

2. I ran cargo install cargo-web from my project's working directory. It failed due to a bunch of obscure errors about dependencies being unable to compile. This made me think the dependencies had been really broken, which gave me a really sour taste in my mouth for Rust.

3. After cloning the dependencies and trying to fix them, I finally realized: cargo install cargo-web is for some reason building for wasm32-unknown-emscripten on my system! 😢

As it turned out, cargo install is respecting my project's .cargo/config target triple.

What I expected

I think that cargo install should ignore the target triple specified in a project directory.

I imagine that at some point or another, most users developing projects primarily targeting wasm/asmjs will run into this issue, and it is incredibly annoying to debug.

I'm using:

$ cargo --version
cargo 1.27.0-nightly (0a1add2d8 2018-04-20)

[vramana]

Hi,

I will work on this bug. I have explored the relevant code a bit. https://github.com/rust-lang/cargo/blob/master/src/bin/cargo/commands/install.rs#L75 Setting the BuildConfig.target to host triplet fixes the bug if I understand it correctly.

https://github.com/rust-lang/cargo/blob/master/src/cargo/util/rustc.rs#L43-L56 host triplet is calculated here. It can be extracted into a seperate function and used in commands/install.rs

How should I add test for this bug?

[rambip]

Is it really solved ?
I'm on rust 1.70.0 and it seems I get the same bug:

# in .cargo/config.toml
[build]
target = "wasm32-unknown-unknown"

And when I use cargo install, I have to specify --target x86_64-unwnown-linux=gnu