clap 3.0 needs a stricter dependency on clap_derive

[dimo414]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Rust Version

rustc 1.63.0 (4b91a6ea7 2022-08-08)

Clap Version

3.0.14

Minimal reproducible code

use clap::Parser;

#[derive(Parser)]
struct Cli {
    #[clap(long)]
    foo: bool,
}

fn main() {
    let cli = Cli::parse();
    println!("foo:{:?}", cli.foo);
}

Steps to reproduce the bug with the above code

The above compiles and runs with the following dependencies:

[dependencies]
clap = { version = "~3.0", features = ["derive"] }
clap_derive = "~3.0"

But removing the clap_derive dependency and clearing Cargo.lock causes the build to fail:

Actual Behaviour

$ cargo build
    Updating crates.io index
   Compiling clap_derive v3.2.18
   Compiling clap v3.0.14
   Compiling clap-demo v0.1.0
error[E0407]: method `from_arg_matches_mut` is not a member of trait `clap::FromArgMatches`
 --> src/main.rs:3:10
  |
3 | #[derive(Parser)]
  |          ^^^^^^
  |          |
  |          not a member of trait `clap::FromArgMatches`
  |          help: there is an associated function with a similar name: `from_arg_matches`
  |
  = note: this error originates in the derive macro `Parser` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0407]: method `update_from_arg_matches_mut` is not a member of trait `clap::FromArgMatches`
 --> src/main.rs:3:10
  |
3 | #[derive(Parser)]
  |          ^^^^^^
  |          |
  |          not a member of trait `clap::FromArgMatches`
  |          help: there is an associated function with a similar name: `update_from_arg_matches`
  |
  = note: this error originates in the derive macro `Parser` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0405]: cannot find trait `CommandFactory` in crate `clap`
 --> src/main.rs:3:10
  |
3 | #[derive(Parser)]
  |          ^^^^^^ not found in `clap`
  |
  = note: this error originates in the derive macro `Parser` (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0412]: cannot find type `Command` in crate `clap`
 --> src/main.rs:3:10
  |
3 | #[derive(Parser)]
  |          ^^^^^^ not found in `clap`
  |
  = note: this error originates in the derive macro `Parser` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider importing this struct
  |
1 | use std::process::Command;
  |
help: if you import `Command`, refer to it directly
  |
3 - #[derive(Parser)]
3 + #[derive(Parser)]
  |

error[E0433]: failed to resolve: could not find `Command` in `clap`
 --> src/main.rs:3:10
  |
3 | #[derive(Parser)]
  |          ^^^^^^ not found in `clap`
  |
  = note: this error originates in the derive macro `Parser` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider importing this struct
  |
1 | use std::process::Command;
  |
help: if you import `Command`, refer to it directly
  |
3 - #[derive(Parser)]
3 + #[derive(Parser)]
  |

Some errors have detailed explanations: E0405, E0407, E0412, E0433.
For more information about an error, try `rustc --explain E0405`.
error: could not compile `clap-demo` due to 5 previous errors

Expected Behaviour

I expected to be able to specify a tilde requirement on 3.0 and be able to use clap_derive, but because clap's Cargo.toml doesn't restrict the upgrade path for its clap_derive dep it pulls down newer, incompatible versions of clap_derive.

Additional Context

I'm planning to upgrade to 3.2 eventually, but for the time being I'm trying to keep a few different projects using the same syntax+version for ease of maintenance. An older project happened to migrate to 3.0 when clap_derive was on 3.1.4 and that worked without issue, but setting up a new project with clap:3.0 failed unexpectedly and confusingly, until I realized a different version of clap_derive was being linked in.

It looks like as of 3.1.9 the dependency on clap_derive was constrained to a nearby version (ed57342), but the 3.0 branch is still broken. It'd be great if a 3.0.15 patch could be cut that fixes this dep.

Debug Output

LMK if you need this.

[epage]

Especially as this is an old release and there is a workaround, I don't see sufficient justification for branching and updating 3.0.x when we've already moved on to 3.1.x, 3.2.x, and 4.0.x. As-is, 3.2.x is in maintenance mode.

[dimo414]

I feel it's still worth cutting a new release so that it continues to compile, as this is a regression from the behavior when the release was published. Although the workaround is straightforward it's totally opaque at the error-site - you have to recognize the compilation errors indicate a bug in a longstanding release of Clap, which isn't intuitive or expected.