clap help trims .0 from float default values

[SzilvasiPeter]

Please complete the following tasks

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

Rust Version

rustc 1.93.0 (254b59607 2026-01-19)

Clap Version

4.5.57

Minimal reproducible code

use clap::Parser;

#[derive(Parser, Debug)]
struct Args {
    #[arg(short = 'a', default_value_t = 1.0)]
    amplify: f32,
}

fn main() {
    let _ = Args::parse();
}

Steps to reproduce the bug with the above code

1. Build and run cargo run -- --help from any workspace containing the code above.
2. Observe the generated help text line for -a argument.

Usage: playground [OPTIONS]

Options:
  -a <AMPLIFY>  [default: 1]
  -h, --help    Print help

Actual Behaviour

Clap displays the default as [default: 1] even though the default_value_t is 1.0.

Expected Behaviour

The help text should show [default: 1.0] for the --amplify argument, so the default is clearly presented as a floating-point value matching the configured literal.

Additional Context

If the 1.1 value is specified, then it displays the default value properly. The zero decimal (X.0) numbers are trimmed.

Debug Output

No response

[epage]

default_value_t relies on Display for the given type. See also https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=db3388422afebd730c7dfcc380fa70af

The only suggestion I have at this time is if it matters, to use a newtype that provides the rendering you expect.