Cargo.toml dependencies: avoid caret requirements

[Marcondiro]

What it does

Hello,
It would be nice to have a lint that highlights the presence of dependencies having the version specified with a ^ (caret) in the Cargo.toml. For example foo="^1.2.3".
As for Cargo docs:

Leaving off the caret is a simplified equivalent syntax to using caret requirements. While caret requirements are the default, it is recommended to use the simplified syntax when possible.

Advantage

This lint helps in having a uniform Cargo.toml where simplified syntax and explicit carets are not mixed, following Cargo docs suggestion.

Drawbacks

None I am aware of

Example

[dependencies]
foo="^1.2.3"
bar="9.8.7"

Could be written as:

[dependencies]
foo="1.2.3"
bar="9.8.7"

[weihanglo]

IMHO, this lint is a better fit in Cargo its own lint system:

• Lint againt non semver-open dependencies cargo#5340
• User control over cargo warnings cargo#12235

[Marcondiro]

@weihanglo are you aware of any policy about what sould go there and what in clippy?
A similar lint is already present in Clippy: https://rust-lang.github.io/rust-clippy/master/index.html#wildcard_dependencies

[weihanglo]

From @flip1995's last comment

Re: Move lints to the cargo repo

cargo lints in Clippy are not the usual Clippy style lints. And I think the cargo team would have a way easier time reviewing cargo lints than the Clippy team.

Should cargo implement the infrastructure to add lints for cargo itself, IMO it should maintain all of the available cargo lints. This includes documentation. Documenting cargo lints on the Clippy website doesn't really make sense to me.

Personally I look forward to the direction, though not sure if it was the decision.
(I am not on Clippy team but Cargo team BTW.)

cc @Muscraft (diagnostics magician on t-cargo)

[Marcondiro]

@weihanglo thanks for the info!
So, if I understand correctly, as for today cargo lints are still a future goal and not something I can use right now to address this issue

[weihanglo]

AFAIK, the only remaining task of stabilizing [lints.cargo] feature is finding a good lint candidate together with the stabilization. This one might be the one. Of course the lint infrastructure is not as polished as clippy's.