Consider interaction between artifact dependencies and required-features

[dtolnay]

Problem

When you use artifact dependency to depend on a binary that has required-features, those features do not get enabled automatically. Should they?

This was not addressed in the artifact dependencies RFC.

Steps

For example the lalrpop package currently contains this binary crate:

[package]
name = "lalrpop"
version = "0.19.12"

[dependencies]
pico-args = { version = "0.4", default_features = false, optional = true }

[[bin]]
name = "lalrpop"
required-features = ["pico-args"]

If something depends on that binary as an artifact dependency, it will fail to build.

[dependencies]
lalrpop = { version = "=0.19.12", artifact = "bin" }

$ cargo check -Z bindeps

error[E0463]: can't find crate for `pico_args`
 --> ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/lalrpop-0.19.12/src/main.rs:2:1
  |
2 | extern crate pico_args;
  | ^^^^^^^^^^^^^^^^^^^^^^^ can't find crate

Possible Solution(s)

I would prefer if required-features of an artifact dependency automatically got enabled.

Notes

Mentioning artifact dependencies tracking issue: #9096

Version

cargo 1.71.0-nightly (9e586fbd8 2023-04-25)
release: 1.71.0-nightly
commit-hash: 9e586fbd8b931494067144623b76c37d213b1ab6
commit-date: 2023-04-25
host: x86_64-unknown-linux-gnu
libgit2: 1.6.3 (sys:0.17.0 vendored)
libcurl: 8.0.1-DEV (sys:0.4.61+curl-8.0.1 vendored ssl:OpenSSL/1.1.1t)
ssl: OpenSSL 1.1.1t  7 Feb 2023
os: Ubuntu 22.04 (jammy) [64-bit]

[dtolnay]

@rustbot label +Z-bindeps

[weihanglo]

I think this is covered by rust-lang/rfcs#3374.

When depending on a binary artifact dependency, Cargo should enable any enable-features features of that binary. This may require plumbing that information into the index so that the dependency and feature resolvers can determine that field is being set. This RFC does not propose a specific plan here, but that it should eventually be supported.

Leave this open as the RFC is not yet merged.

[Nemo157]

It seems like it should at least error earlier currently, if the required features are not active it should not be attempting to build the binary at all.