Addition of --keep-going flag breaks analysis on older repos

[vitalytarasov]

Addition of --keep-going flag in v0.3.2037 breaks code analysis on older repos. Analyzer terminates with error:

2024-08-16T17:38:57.220808Z ERROR FetchBuildDataError:
error: the --keep-going flag is unstable, and only available on the nightly channel of Cargo, but this is the stable channel
See https://doc.rust-lang.org/book/appendix-07-nightly-rust.html for more information about Rust release channels.
See rust-lang/cargo#10496 for more information about the --keep-going flag.
rust-analyzer version: 0.3.2070

rustc version: 1.70.0 (set via rust-toolchain file)

editor or extension: VSCode

relevant settings: default settings

workaround: downgrade rust-analyzer to v0.3.2029

[Veykril]

We are aware of this, either upgrade your toolchain or if thats not possible install the rust-analyzer component in your toolchain and point your editor to use that rust-analyzer instead. We cannot reasonably support older rust versions.

[vitalytarasov]

Why not pass the flag conditional of rustc version?

[Veykril]

See #17662 and #17561

[IoIxD]

For those from Google for the same reason I am (I was forced to use an older Rust version due to an esoteric compile target), do know that while you can't remove this flag in your own config, you can compile the 2023-03-27 branch, install it on a seperate place on your computer, and then configure your repo to use that binary instead.

{
    "rust-analyzer.server.path": "/opt/rust-analyzer/rust-analyzer"
}

[jtmoon79]

Is it possible to add a setting that would drop the --keep-going flag?

[ChayimFriedman2]

@jtmoon79 Adding a flag won't be easier and will be worse than automatically detecting whether the toolchain supports it. But this is not the problem. By this date the flag is almost two years old, and like @Veykril said above we cannot support every Rust version forever. If you must use an old Rust toolchain, pin your rust-analyzer or override the Cargo command, but beware that overriding may not work well.