Get Unknown configuration option rust-version when running the rust format command

[HaoYang670]

Describe the bug
On my desktop, when I run the command

cargo +stable fmt --all -- --check

I always get the warning

Warning: Unknown configuration option `rust-version`

When I run the command

rustfmt --help=config

I could not find a configuration option called rust-version
I am not sure whether it is a bug or my problem.

To Reproduce
Run the command

cargo +stable fmt --all -- --check

Expected behavior
Remove the warning.

Additional context
Developer's guide to Arrow Rust.

[HaoYang670]

Should we delete this line:
https://github.com/apache/arrow-rs/blob/master/rustfmt.toml#L19

I do not find the configuration rust-version in other project's rustfmt file, such as:
https://github.com/apache/arrow-datafusion/blob/master/rustfmt.toml

[HaoYang670]

Does anyone meet the same problem?

[HaoYang670]

@alamb Could you reproduce the problem?

[alamb]

Hi @HaoYang670 -- I do see the same problem and I agree with your assessment of the problem.

I had assumed it was related to not using nightly, but it happens for me with nightly and with stable rust.

cd /Users/alamb/Software/arrow-rs && CARGO_TARGET_DIR=/Users/alamb/Software/df-target cargo fmt
Warning: Unknown configuration option `rust-version`
Warning: Unknown configuration option `rust-version`
Warning: Unknown configuration option `rust-version`

cargo +nightly  fmt
Warning: Unknown configuration option `rust-version`
Warning: Unknown configuration option `rust-version`
Warning: Unknown configuration option `rust-version`