Stack overflow on virtual project with patched dependencies which point at each other

[handicraftsman]

Literally this

handicraftsman@NickolayPC:~/Projects/airkit$ cargo build --verbose

thread 'main' has overflowed its stack
fatal runtime error: stack overflow
Aborted

Steps

1. Create a root project Cargo.toml with [workspace] section and [patch.crates-io] section

[workspace]
members = [
    "auragfx",
    "auragfx-backend-glutin"
]

[patch.crates-io]
auragfx = { path = "./auragfx" }
auragfx-backend-glutin = { path = "./auragfx-backend-glutin" }

2. Create other two manifests

[package]
name = "auragfx"
version = "0.1.0"
authors = ["handicraftsman <nickolay02@inbox.ru>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[features]
default = ["backend-glutin"]

backend-glutin = ["auragfx-backend-glutin"]

[dependencies]
spirv_cross = "0.15.0"
shaderc = "0.6.0"

auragfx-backend-glutin = { version = "0.1.0", optional = true }

[package]
name = "auragfx-backend-glutin"
version = "0.1.0"
authors = ["handicraftsman <nickolay02@inbox.ru>"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
auragfx = "0.1.0"
glutin = "0.21.0"
gl = "0.13.0"

3. ???

Notes

Output of cargo version:

cargo 1.38.0-nightly (e3563dbdc 2019-07-16)

[ehuss]

I've narrowed this down to a test case:

#[cargo_test]
fn cycle() {
    Package::new("a", "1.0.0").publish();
    Package::new("b", "1.0.0").publish();
    let p = project()
        .file("Cargo.toml",
            r#"
            [workspace]
            members = ["a", "b"]

            [patch.crates-io]
            a = {path="a"}
            b = {path="b"}
            "#)
        .file("a/Cargo.toml",
            r#"
            [package]
            name = "a"
            version = "1.0.0"

            [dependencies]
            b = "1.0"
            "#)
        .file("a/src/lib.rs", "")
        .file("b/Cargo.toml",
            r#"
            [package]
            name = "b"
            version = "1.0.0"

            [dependencies]
            a = "1.0"
            "#)
        .file("b/src/lib.rs", "")
        .build();

    p.cargo("check").run();
}

This gets caught in a cycle in metadata_of.

@Eh2406 or @alexcrichton, I could have sworn the resolver had some cycle detection, but it doesn't seem to trigger in this case with [patch]. I don't think I know enough about the resolver to investigate more.

EDIT: The Package::new at the top isn't necessary. It can also be crate::support::registry::init();.

[Eh2406]

Thanks @ehuss, I have not looked into this yet but here are some links.
The cycle detection is check_cycles.
I would guess that it is related to #7118.

[handicraftsman]

Well, i understand what needs to be done to resolve this for me and what is wrong in project layout. But yeah, not giving a proper error is definitely user friendly 😸

[ehuss]

@handicraftsman You can't have a cycle in your dependency graph. You'll need to restructure so that auragfx and auragfx-backend-glutin don't depend on one another.

[handicraftsman]

Yeah, already noticed that as i've said above. Already done.

[ehuss]

Yeah, already noticed that as i've said above. Already done.

Oh, haha, I misread. 😄

[alexcrichton]

I believe the bug is this line which returns a false negative for matches_id when using [patch]. Instead that code should be using something like deps where it returns (&PackageId, &[Dependency]) only we'll need to update the implementation of Resolve::deps_not_replaced to return this (basically be the same-ish implementation of Resolve::deps