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Call for Testing: MSRV-aware resolver #13873

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epage opened this issue May 7, 2024 · 6 comments
Open

Call for Testing: MSRV-aware resolver #13873

epage opened this issue May 7, 2024 · 6 comments
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A-dependency-resolution Area: dependency resolution and the resolver S-waiting-on-feedback Status: An implemented feature is waiting on community feedback for bugs or design concerns.

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@epage
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epage commented May 7, 2024 •
edited

Call for testing

The MSRV-aware resolver part of this RFC is implemented and we are wanting to collect feedback in preparation for stabilization.

The goal is to allow you to manage your dependencies without having to manually ensure they are compatible with your rust-version

  • When stabilized, this will be opt-in. When upgrading to the 2024 Edition, it will be the opt-out.
  • It uses package.rust-version if set, otherwise rustc --version
  • It won't fail if there isn't a MSRV-compatible version but instead it will pick a compatible version

Basic steps:

Requirements:

  • 1.80.0-nightly (9c9b56879 2024-05-05) or newer
  • beta
  • stable

At minimum, run

$ CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-rust-version cargo +nightly -Zmsrv-policy generate-lockfile

NOTE: The config field name and values are intentionally not ready yet. This is being tracked in #13540. This will be resolved before stabilization

Feel free to run any other commands and workflows with

  • CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-rust-version (proposed behavior) or CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-maximum (existing behavior) with +nightly -Zmsrv-policy
    • You could also set them via .cargo/config.toml
  • workspace.resolver = "3" or package.edition = "2024" with cargo-features = ["edition2024"] in your Cargo.toml

See also Documentation

Please leave feedback on this issue
@epage epage added A-dependency-resolution Area: dependency resolution and the resolver S-waiting-on-feedback Status: An implemented feature is waiting on community feedback for bugs or design concerns. labels May 7, 2024
@epage epage mentioned this issue May 7, 2024
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@Nemo157
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Nemo157 commented May 8, 2024

Initial impressions, when I ran this command in a project (https://github.com/Nemo157/u2f-touch-detector @ e12096fe3571ac3b7c501dca9f9d452b2b9f0e4c) it emitted what looked like a bunch of warnings to me:

> CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-rust-version cargo -Zmsrv-policy generate-lockfile
    Updating crates.io index
     Locking 101 packages to latest Rust 1.79.0 compatible versions
      Adding addr2line v0.21.0 (latest: v0.22.0)
      Adding gimli v0.28.1 (latest: v0.29.0)
      Adding io-lifetimes v1.0.11 (latest: v2.0.3)
      Adding linux-raw-sys v0.4.13 (latest: v0.6.4)
      Adding nix v0.27.1 (latest: v0.28.0)
      Adding nu-ansi-term v0.46.0 (latest: v0.50.0)
      Adding object v0.32.2 (latest: v0.35.0)
      Adding owo-colors v3.5.0 (latest: v4.0.0)
      Adding regex-automata v0.1.10 (latest: v0.4.6)
      Adding regex-syntax v0.6.29 (latest: v0.8.3)
      Adding windows-sys v0.48.0 (latest: v0.52.0)
      Adding windows-targets v0.48.5 (latest: v0.52.5)
      Adding windows_aarch64_gnullvm v0.48.5 (latest: v0.52.5)
      Adding windows_aarch64_msvc v0.48.5 (latest: v0.52.5)
      Adding windows_i686_gnu v0.48.5 (latest: v0.52.5)
      Adding windows_i686_msvc v0.48.5 (latest: v0.52.5)
      Adding windows_x86_64_gnu v0.48.5 (latest: v0.52.5)
      Adding windows_x86_64_gnullvm v0.48.5 (latest: v0.52.5)
      Adding windows_x86_64_msvc v0.48.5 (latest: v0.52.5)

Looking into the lockfile this had nothing to do with the MSRV clause though, this is just the transitive version requirements of my dependencies, so the same messages are emitted without the msrv-policy. It seems like there should be some distinction in these messages about why the latest isn't being selected.

I tried to force a MSRV conflict by extracting eyre@0.6.12 into a local directory, adding a patch.crates-io pointing to it, and bumping it to have version = "0.6.13" and rust-version = "1.80.0". Running the above command seemed to ignore that and still chose to use the local 0.6.13 version instead of the remote 0.6.12; but maybe there's something specifically about patch/path dependencies causing that.

@Nemo157
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Nemo157 commented May 9, 2024

I came up with a different scheme for testing a current-rustc MSRV conflict, I overlaid a nightly cargo version on top of a stable 1.72 toolchain (I have no idea if something like this is possible with rustup, but it's easy to do with oxalica/rust-overlay with nix):

> nix shell pkgs#rust-bin.stable.'"1.72.0"'.minimal
> nix shell pkgs#rust-bin.nightly.latest.cargo
> cargo --version && rustc --version
cargo 1.80.0-nightly (0ca60e940 2024-05-08)
rustc 1.72.0 (5680fa18f 2023-08-23)

Regenerating the lockfile seemed to happen just as before, but correctly detected 1.72:

> CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-rust-version cargo -Zmsrv-policy generate-lockfile
    Updating crates.io index
     Locking 101 packages to latest Rust 1.72.0 compatible versions
      ... same as before ...

Trying to build then failed

> cargo check
error: rustc 1.72.0 is not supported by the following packages:
  clap@4.5.4 requires rustc 1.74
  clap_builder@4.5.2 requires rustc 1.74
  clap_derive@4.5.4 requires rustc 1.74
  clap_lex@0.7.0 requires rustc 1.74
Either upgrade rustc or select compatible dependency versions with
`cargo update <name>@<current-ver> --precise <compatible-ver>`
where `<compatible-ver>` is the latest version supporting rustc 1.72.0

I would have expected a warning about this when generating the lockfile (maybe even mentioning the latest compatible version so I didn't have to go searching the repository for when clap's MSRV was last bumped).

Setting the minimum requirement on clap back to a compatible version, regenerating the lockfile and building worked, but as I mentioned above there's no distinction that the reason the latest wasn't chosen was MSRV related rather than version constraint related

> cargo add clap@4.4.18
    Updating crates.io index
      Adding clap v4.4.18 to dependencies
             Features:
             ...

> CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-rust-version cargo -Zmsrv-policy generate-lockfile
    Updating crates.io index
     Locking 101 packages to latest Rust 1.72.0 compatible versions
      Adding addr2line v0.21.0 (latest: v0.22.0)
      Adding clap v4.4.18 (latest: v4.5.4)
      Adding clap_builder v4.4.18 (latest: v4.5.2)
      Adding clap_derive v4.4.7 (latest: v4.5.4)
      Adding clap_lex v0.6.0 (latest: v0.7.0)
      ... rest same as before ...

> cargo check
    ...
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 12.62s

@epage
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epage commented May 9, 2024

We have two challenges with the reporting

As for having too high of version requirements, I wonder how often that will be happening in practice. Users get their version requirements from

  • cargo add: will auto-select a compatible version
  • crates.io: shows what the MSRV is

Hopefully this isn't a high traffic workflow that we have to worry about. Instead, we also expect people to see these messages when they are intentionally not using the MSRV-aware resolver where there is nothing actionable from the messages and they will likely annoy people.

I think I'd be ok with experimenting with adding to Adding line a requires Rust 1.74.0 but also saying what an alternative is might be a bit too noisy.

@Xaeroxe
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Xaeroxe commented May 10, 2024 •
edited

This works great for the which crate. We've previously struggled with this issue, so thanks a bunch for devoting attention to it!

$ CARGO_RESOLVER_SOMETHING_LIKE_PRECEDENCE=something-like-rust-version cargo +nightly -Zmsrv-policy generate-lockfile
    Updating crates.io index
     Locking 36 packages to latest Rust 1.63 compatible versions
      Adding home v0.5.5 (latest: v0.5.9)
      Adding linux-raw-sys v0.4.13 (latest: v0.6.4)
      Adding regex v1.9.6 (latest: v1.10.4)
      Adding regex-automata v0.3.9 (latest: v0.4.6)
      Adding regex-syntax v0.7.5 (latest: v0.8.3)
      Adding windows-sys v0.48.0 (latest: v0.52.0)
      Adding windows-targets v0.48.5 (latest: v0.52.5)
      Adding windows_aarch64_gnullvm v0.48.5 (latest: v0.52.5)
      Adding windows_aarch64_msvc v0.48.5 (latest: v0.52.5)
      Adding windows_i686_gnu v0.48.5 (latest: v0.52.5)
      Adding windows_i686_msvc v0.48.5 (latest: v0.52.5)
      Adding windows_x86_64_gnu v0.48.5 (latest: v0.52.5)
      Adding windows_x86_64_gnullvm v0.48.5 (latest: v0.52.5)
      Adding windows_x86_64_msvc v0.48.5 (latest: v0.52.5)
$ cargo +1.69.0 build
   Compiling rustix v0.38.34
   Compiling bitflags v2.5.0
   Compiling linux-raw-sys v0.4.13
   Compiling home v0.5.5
   Compiling either v1.11.0
   Compiling which v5.0.0 (~/Documents/source_code/which-rs)
    Finished dev [unoptimized + debuginfo] target(s) in 1.00s

@Xaeroxe Xaeroxe mentioned this issue May 10, 2024
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@Darksonn
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What is the syntax for configuring this using .cargo/config.toml? I could not figure it out.

Is there an option for using dependencies compatible with whichever rustc the user happens to be using?

@weihanglo
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What is the syntax for configuring this using .cargo/config.toml? I could not figure it out.

Is there an option for using dependencies compatible with whichever rustc the user happens to be using?

This should work.

[unstable]
msrv-policy = true # or put this in CLI `-Zmsrv-policy`

[resolver]
something-like-precedence = 'something-like-rust-version'

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