Cargo doesn't execute per-target runner for target set in Cargo.toml (per-package-target)

[elaforma]

Problem

I'm working on an embedded Rust project. In order to be able to run it using cargo run, I use the target.<triplet>.runner attribute in .cargo/config.toml to launch an emulator. The target also used to be set in config.toml.

Recently, in order to use the xtask pattern, I decided to try out the per-package-target feature (#9406). I removed the target from config.toml and added a forced-target field to my Cargo.toml. Unfortunately, now cargo no longer executes my runner, instead trying to execute the binary directly (which, of course, doesn't work).

Cargo is building for the correct target, but for some reason not taking this into account when deciding whether or not to use the runner. Manually passing the --target option solves this issue, but that's exactly what I'm trying to avoid by using this feature.

Steps

1. Create a #![no_std] project for a different target triplet
2. Specify a runner for this triplet in .cargo/config.toml
3. Use the per-package-target cargo feature and the default-target or forced-target keys in Cargo.toml to specify the triplet
4. cargo run without a --target option
5. Observe that cargo is building for the correct triplet, but not using the runner.

Possible Solution(s)

There are multiple other issues (e.g. the -Zbuild-std one in #9451) that suggest cargo assumes it's building for the host during various stages of the build if no --target flag is passed. I don't know enough about the internals of cargo to tell if this is what's happening here.

Notes

No response

Version

cargo 1.63.0-nightly (8d42b0e87 2022-06-17)

[4LT]

Possible duplicate of #10518 ?

[ehuss]

Ah, yes, closing as a duplicate of #10518.