Rustdoc re-exports only include one item per name across all namespaces

[obi1kenobi]

I tried this code:

//! This crate exports the following:
//! - the function `Foo`, also as `Bar` and `nested::Foo`
//! - the type `Foo`, also as `Bar` and `nested::Foo`

pub mod nested {
    pub struct Foo {}

    #[allow(non_snake_case)]
    pub fn Foo() {}
}

pub use nested::Foo;
pub use Foo as Bar;

// Proof that both the type and the function are visible.
// Not exported.
#[allow(dead_code)]
fn proof() -> Bar {
    Bar();
    Bar {}
}

I expected to see this happen: generated rustdoc JSON should include "import" items that point to both the function and the type named Foo, for each of the re-exported Foo and Bar names.

Instead, this happened: the rustdoc JSON only one "import" item for Foo and one for Bar, both pointing to the function. No re-export items pointing to the struct were present, as if the struct was not re-exported (even though the proof() function shows it is).

These are the only "kind": "import" items present in the rustdoc JSON.

{
    // ...
    "kind": "import",
    "inner": {
        "source": "nested::Foo",
        "name": "Foo",
        "id": "0:5:1592",
        "glob": false
    }

    // ...
    "kind": "import",
    "inner": {
        "source": "Foo",
        "name": "Bar",
        "id": "0:5:1592",
        "glob": false
    }
}

This is the item those point to:

"0:5:1592": {
    "id": "0:5:1592",
    "crate_id": 0,
    "name": "Foo",
    "span": {
        "filename": "src/lib.rs",
        "begin": [
            18,
            4
        ],
        "end": [
            18,
            19
        ]
    },
    "visibility": "public",
    "docs": null,
    "links": {},
    "attrs": [
        "#[allow(non_snake_case)]"
    ],
    "deprecation": null,
    "kind": "function",
    // ...
}

This issue originally came up as obi1kenobi/cargo-semver-checks#343, since clap v3.2.0 re-exports a trait and a derive macro that have the same name.

trustfall-rustdoc-adapter PR obi1kenobi/trustfall-rustdoc-adapter#72 includes this failing test case.

Meta

rustc --version --verbose:

$ rustc --version --verbose
rustc 1.69.0-nightly (d7948c843 2023-01-26)
binary: rustc
commit-hash: d7948c843de94245c794e8c63dd4301a78bb5ba3
commit-date: 2023-01-26
host: x86_64-unknown-linux-gnu
release: 1.69.0-nightly
LLVM version: 15.0.7

Also present in 1.67 and 1.68.0-beta.1 (efd2745 2023-01-25).

[obi1kenobi]

It seems like the simplest fix would be to have rustdoc JSON emit multiple "import" entries, one per "id" that is pointed to and with duplicated names. That appears to be both forward and backward compatible.

[obi1kenobi]

@rustbot label T-rustdoc

[GuillaumeGomez]

It's working for the HTML output too.

[obi1kenobi]

Thanks for the fix, much appreciated! 🎉