Correctly identify and distinguish crates in the dependency tree

[nicola-gigante]

Hi all,

I would need to distinguish crates in the dependency tree with the maximum fidelity.

I have a few questions when using display_name() and origin() for my purposes.

1. To start, one thing I've noticed is that if I have a renamed dependency in Cargo.toml such as:

   [dependencies]
   renamed-crate = { package = "my-crate", version = "0.42" }
   

   What I get from hir::Crate::display_name() is still "my-crate" instead of "renamed-crate". However the latter is useful
   because it's how the crate can be named in the source code. How do I get to this name?

2. Another issue is that Cargo allows different crates from different registries to have the same name and even the same version.
   In this case it seems to me that both display_name() and version() would be equal, and there is nothing in hir::Crate about the source registry. Is there a permanent way to distinguish two crates with the same name and version coming from different registries? By permanent I mean that is reproducible across different calls of the tool and of RA, so not the actual salsa id of the hir::Crate.

3. In all my tests I get that the crate_name() and canonical_name() of the crate's display_name() are the same. What's the difference between the two?

Thanks, any help is appreciated :)

[ChayimFriedman2]

Crates don't have names. They sometimes have display names, which are not required to be unique and are not used for anything other than presentation.

Dependencies have names. When you rename the crate in Cargo.toml, you rename the dependency. A Dependency carries a name you can check.

The difference between canonical name and crate name is that crate_name has dashes replaced with underscores.

[nicola-gigante]

I see what you mean by "crates do not have names", but still cargo uses the name declared in the package manifest to identify them somehow.

For example if I have two different packages which declare the same name (e.g. "dependency") and same version (e.g. "0.1.0") and I depend on both (renaming them) from a third package, I get this:

$ cargo build
error: package collision in the lockfile: packages dependency v0.1.0 (/Users/gigabytes/scratch/dependency) and dependency v0.1.0 (/Users/gigabytes/scratch/other/dependency) are different, but only one can be written to lockfile unambiguously

So it seems that the combination of display_name and version do matter in the sense that I cannot have collisions in a dependency tree, at least as far as cargo-managed projects are concerned. Is this correct? I'm sorry, I realize this is more a question about cargo than about rust analyzer but it's relevant to how I use RA in my project.

Also for the crate_name/canonical_name question: that is not what I'm observing. I have a crate called test-crate in the manifest and I see test_crate in both when I print them. What am I missing?

[ChayimFriedman2]

In Cargo name is a required manifest property. In other build systems not necessarily. rustc is not concerned with crate names, neither rust-analyzer.

In Cargo, the manifest's name should be the same as the display name.

Also for the crate_name/canonical_name question: that is not what I'm observing. I have a crate called test-crate in the manifest and I see test_crate in both when I print them. What am I missing?

Weird. This should not happen.

[nicola-gigante]

I see, thanks.

For the names, I do this, where dep is the CrateDependency:

println!("dep name: {:?}", dep.name);
println!("origin: {:?}", dep.krate.origin(self.sema.db));
println!("display name: {:?}", krate.display_name(self.sema.db));

and I get (for the crate that has "test-crate" as name in the manifest):

dep name: Name { symbol: "test_crate", ctx: () }
origin: Local { repo: None, name: Some("test-crate") }
display name: Some(CrateDisplayName { crate_name: CrateName("test_crate"), canonical_name: "test_crate" })

So the "dashed" name survives in the origin, but not in the display name, apparently.