cargo: home does not compile on wasm

Problem

The home crate does not build for wasm32-unknown-unknown. I encountered this through a transitive dependency from another crate.

Steps

$ cargo new bugreport
$ cd bugreport
$ echo 'home = "0.5"' >> Cargo.toml
$ cargo build --target wasm32-unknown-unknown

results in error:

error[E0425]: cannot find function `home_dir_inner` in the crate root
  --> .cargo/registry/src/index.crates.io-6f17d22bba15001f/home-0.5.5/src/env.rs:33:16
   |
33 |         crate::home_dir_inner()
   |                ^^^^^^^^^^^^^^ not found in the crate root

Possible Solution(s)

Home has no obvious place in wasm, so I suggest adding the following (and I’m happy to add this myself, along with CI test on wasm target)

#[cfg(target_arch = "wasm32")]
fn home_dir_inner() -> Option<PathBuf> {
    None
}

Notes

No response

Version

No response

About this issue

Original URL
State: open
Created a year ago
Comments: 20 (17 by maintainers)

Most upvoted comments

I’m going to cancel the FCP here since I don’t think it is likely to move forward.

@rfcbot cancel

The team would like to see someone open an ACP as mentioned above in https://github.com/rust-lang/cargo/issues/12297#issuecomment-1707097192. @joshtriplett (who is also on the libs team) has also indicated they would like to see that route move forward.

ehuss on Feb 8, 2024

Yup, I’ll see if I can squeeze out an ACP.

djc on Sep 6, 2023

@djc we talked about this in the cargo team meeting and we are interested in the help. Additionally, we feel more of that time should probably be spent towards an ACP to merge this into the standard library as there is interest in such a thing

Independent of helping with home, is that something you’d be willing to take on?

epage on Sep 5, 2023

Sorry I was taking a break for a while and this issue then escaped me. I think adding support for wasm doesn’t make much sense anyways since its not a nix or windows platform. In addition, I don’t think any of us have the bandwidth to figure that out at the moment.

LucioFranco on Aug 9, 2023

My take is that home is primarily for rustup and cargo. I checked my box on this change because it is a relatively small change with what I think is little impact. But I think I would be against larger changes unless they are specifically to support cargo and rustup. So my perspective is to provide support on an as-available basis (like very small changes), but otherwise not accept larger changes.

We should have tagged @LucioFranco, since they said they would help with maintaining it. That’s not a process we have handled too well.

ehuss on Jun 27, 2023

I am pretty into this suggestion, similar to what you’ve proposed.

My suggestion would be to have home_dir return None, for now. That way, we don’t need to block you here, and an implementation can be added later if we figure out what it should do.

std::env::home_dir also returns a None on unsupported platforms despite its deprecation.

I want to expand the proposal to align with things mentioned above — returns None on currently unsupported platforms. Simply starting from this:

/// Returns `None` on unsupported platforms.
///
/// We can figure out the implementation of each platform when needed.
#[cfg(not(any(unix, target_os = "redox", windows)))]
fn home_dir_inner() -> Option<PathBuf> {
    None
}

Let’s do a quick poll.

@rfcbot fcp merge

weihanglo on Jun 22, 2023