Expose a function to obtain cargo's installation root

[yds12]

Problem

I have an application that needs to know where binaries installed via cargo install are located in the system. I can roughly assume it will be in $HOME/.cargo/bin, but according to this, when we do cargo install the location will be determined by, in order of priority:

• --root option
• CARGO_INSTALL_ROOT environment variable
• install.root Cargo config value
• CARGO_HOME environment variable
• $HOME/.cargo

My idea was to use cargo as a library crate (although I need to see the impact in terms of dependencies) to obtain this location. I assume cargo already has some internal function that does that, as far as I checked it uses a resolve_root function, but that function is not public.

In summary: it would be nice to have a function in cargo (as a library) that given a current working directory, could give me the installation root.

Proposed Solution

If I understand correctly, making resolve_root public would suffice.

Notes

No response

[epage]

Could you go into detail on why you need to know where the install directory is? That can help making sure we talk about a solution that is relevant to your problem. For example, if the user sets --root, then I don't think we track that for you. If they set it via config, then looking it up is dependent on what directory you are in.

[yds12]

Hi, thanks for the quick feedback! So, given a certain system-wide available binary x I need to be able to tell if x was installed via cargo, or not. The reason is that we want to take different actions depending on that. My idea was to compare the output of something like which x with cargo's install root to be able to say "yes, it was installed via cargo". I'm doing this in a "best-effort" basis, so it's ok if I miss the case when the user used --root or something of that sort.

I just noticed that I can also do cargo install --list to get the names of executables installed by cargo (although that would require me to shell -- for context, I'm doing this from rust code). That is enough to solve my problem, so if this feature is too niche, feel free to close the issue.

[epage]

So the request isn't "list of binaries cargo installed" but "list of binaries installed into the common location", right?

That reduces your look up to

• CARGO_HOME environment variable
• $HOME/.cargo

which is covered by home::cargo_home.

We might be adding more paths in the future for XDG support (see https://internals.rust-lang.org/t/pre-rfc-split-cargo-home/19747) but that would likely be a more specific entry point in home (e.g. cargo_install_dir)

[yds12]

Shouldn't I also check CARGO_INSTALL_ROOT, in case the user has modified that?

[epage]

That depends. CARGO_INSTALL_ROOT is exactly the same as install.root and most users who want it more permamently set would likely use install.root instwad, so I see CARGO_INSTALL_ROOT as more of a transient property which means you likely can't rely on it.