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2024 Deprecations

Problem

Cargo has been emitting a bunch deprecation message for a (long?) while. Since edition 2024 is approaching (1.82.0 anticipated), and a Cargo linting system is on the way (https://github.com/rust-lang/cargo/pull/13621), we might want to take advantage of this timing to evaluate whether this deprecations could be turned into a hard error.

The main risk here is CI automation might fail. Unlike rustc and clippy lints, people hardly noticed Cargo warnings becuase because there was no way to set -D on them.

Deprecations

2024 Edition

dependency without path, version, git, workspace specified

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/cargo/util/toml/mod.rs#L1914-L1918

license-file and readme pointing to a non-existent file

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/ops/cargo_package.rs#L416-L418

dev_dependencies/build_dependencies/default_features/crate_types/proc_macro

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/util/toml/mod.rs#L198-L199

  • Warn since: 1.61 (2022-05-19) but only when conflicting with dash ones
  • may become a hard error? NO
  • Risk: Old crates fail to compile. Might need an edition boundary.
  • https://github.com/rust-lang/cargo/pull/10316
  • Next step:
    • Error on 2024 edition

good old [project] (replaced with [package])

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/util/toml/mod.rs#L497-L498

default-features in inherited dependencies

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/util/toml/mod.rs#L1801-L1803

plugin support

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/util/toml/targets.rs#L211-L216

  • Warn since: 1.77.0 (2024-03-21)
  • may become a hard error? ✅ (stop supporting plugin)
  • Risk: Too new.
  • https://github.com/rust-lang/cargo/pull/13248
  • Next step:
    • Wait until 2024 release
    • Remove key, making it an "unused key" warning

Independent of Edition

--release is ignored when paired with --profile

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/cargo/util/command_prelude.rs#L570-L573

  • Warn since: 1.57.0 (2021-12-02)
  • may become a hard error? ✅
  • Risk: Break people's build. Easy to fix by themselves.
  • https://github.com/rust-lang/cargo/pull/9943
  • Next step:
    • Check with ehuss, is hard error justified? If accepted for long time and no indication to user its a bug, then maybe keep as warning?

cargo read-manifest

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/bin/cargo/commands/read_manifest.rs#L9

  • Warn since: Merged on 2016-10-03.
  • Become a hard error? NO
  • Risk: Automations might still rely on it. cargo metadata --no-deps should cover its use cases.
  • https://github.com/rust-lang/cargo/pull/3150
  • Next step:
    • Add runtime warning saying its deprecated (not just help)
    • CLI, so no further steps

[replace] is deprecated

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/doc/src/reference/overriding-dependencies.md?plain=1#L300-L301

  • Warn since: 1.42.0 (2020-03-12)
  • may become a hard error? NO
  • Risk: Can we patch [patch] to fully replace [repalce]?
  • https://github.com/rust-lang/cargo/pull/7733
  • Next step
    • Deprecation warning using lint system (since restricted Cargo.toml)
    • Maybe with future edition turn it into forbid (based on people's reaction to warning)

old cargo tree flags: --all, no-dev-dependencies, --no-indent, --prefix-depth, --all-targets

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/bin/cargo/commands/tree.rs#L144-L146

  • Warn since: 1.44.0 (2020-06-04)
  • may become a hard error? ✅ for all; NO for others
  • Risk: Have alternatives. Easy to fix.
  • https://github.com/rust-lang/cargo/pull/8115
  • Next step:
    • Downgrade to consistent deprecation (no point removing one when others would be kept)

path override modifying dependency graph

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/core/registry.rs#L535-L538

  • Warn since: Merged on 2016-10-05 (1.14 or so)
  • may become a hard error? ✅ (was a bug)
  • Risk: Assuming people seldom use it?
  • https://github.com/rust-lang/cargo/pull/3136
  • Next step:
    • Turn into error because it was a bug with buggy behavior and people using this went into it knowing its bad (since they likely started post-1.14), and we've not been getting necro-posts for people saying they need this (like depending on bins)

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/core/compiler/custom_build.rs#L850-L856

user-defined alias is shadowing an external subcommand found:

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/bin/cargo/cli.rs#L321-L323

  • Warn since: 1.58.0 (2022-01-13)
  • may become a hard error? ✅
  • Risk: Custom workflow might fail. cargo clippy and cargo fmt are what we concerned.
  • #10049
  • https://github.com/rust-lang/cargo/pull/10082
  • Next step:
    • Turn into hard error. Aliases are generally for user interaction, rather than automation (except for things like xtasks) so the impact is low

output artifact name collisions

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/core/compiler/build_runner/mod.rs#L472-L474

  • Warn since: 1.32.0 (2019-01-17)
  • may become a hard error? ✅
  • Risk: Workaround could be quite complicated.
  • https://github.com/rust-lang/cargo/pull/6308
  • Next step:
    • Maybe in a future Edition, switch to forbid by default?
    • Or just warn because this is implementation-defined for when a collision may occur and new collisions may come up in the future

https://github.com/rust-lang/cargo/blob/f0ae76519127d16d87362c6d88416d92cba86c6a/src/cargo/core/compiler/mod.rs#L1427-L1430

  • Warn since: 1.24.0 (2018-02-15)
  • may become a hard error? ✅
  • Risk: People depend on this in a quirky way.
  • https://github.com/rust-lang/cargo/pull/4797
  • Next step:
    • Needs investigation into replacement feature for those relying on it
    • Likely should instead be hard error conditioned on Edition

Ambiguous package name in git dependency

https://github.com/rust-lang/cargo/blob/bd1cf584af2c356eeb3980c3c9bb0fea190ed633/src/cargo/ops/cargo_read_manifest.rs#L225-L234

  • Warn since: 1.63
  • may become a hard error? NO
  • Risk: too many false positives, see #10752
  • #10701, #10767
  • Next step:
    • Address #10752
    • Turn into error on edition

No further steps

deprecate --all (alias to --workspace)

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/cargo/util/command_prelude.rs#L54

  • Warn since: 1.39.0 (2019-11-07)
  • may become a hard error? NO
  • Risk: Automations might still rely on it. Some users use it exclusively due to brevity (see also #11554)
  • https://github.com/rust-lang/cargo/pull/7241
  • Next step:
    • CLI, so no further steps
    • Not doing runtime warning because of pervasive use by people who really like it for brevity

Deprecate .cargo/config

https://github.com/rust-lang/cargo/blob/8bcecfeed464c990733ff680e0b4546a73fbed44/src/cargo/util/context/mod.rs#L1563-L1567

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rust-cargo-team
Cargo team for the Rust Programming Language
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