doctest builds have a different working directory in virtual workspaces that breaks proc-macros that read relative paths

[leighmcculloch]

I tried this code in a crate that is in a virtual workspace:

#[proc_macro]
pub fn mymacro(_metadata: TokenStream) -> TokenStream {
    _ = fs::read("relativefilepath").unwrap();
    // ...
}

I expected to see this happen:

• When the relative file path is present relative to the root of the workspace, I expected to see builds, tests, and doctests for the crate to pass.

Instead, this happened:

• Builds and tests both pass, as the file is found.
• Doctests fail to compile, stating that the file cannot be found.

It appears that in a virtual workspace that:

• In build, test: the current working directory is the root of the workspace.
• In doctest: the current working directory is the root of the crate where the doctest lives.

The current working directory should be consistent between build, test, and doctest, otherwise proc-macros that load files cannot reliably and consistently load a relative path.

Meta

rustc --version --verbose:

rustc 1.63.0 (4b91a6ea7 2022-08-08)
binary: rustc
commit-hash: 4b91a6ea7258a947e59c6522cd5898e7c0a6a88f
commit-date: 2022-08-08
host: aarch64-apple-darwin
release: 1.63.0

[ehuss]

Thanks for the report! This is a known issue, with a fix available via -Z doctest-in-workspace. Closing as a duplicate of rust-lang/cargo#9427