"duplicated RLS configuration" each time RLS is started inside VSCode

I've been through the same problem. I am not exactly sure of the proper solution but these workarounds have solved my problem.

1. Remove all VSCode extensions that are Rust-related.
2. Remove any Rust-related configuration in VSCode settings.json.
3. If you are using Linux and you have done a lot of playing around, sometimes $HOME/.cargo/registry may be corrupt, so remove that folder if it helps.
4. Restart VSCode.

5. Install these extensions in order:

   • Rust RLS official extension

     Do not install Rust kalitaalexey (Seems to be the conflicting cause).

   • Rust Assist extension.

   • vscode-rust-syntax extension.

   • vsc-rustfmt extension.

   • Cargo extension.

   • Better TOML

The combination of these extensions work OK for me. Specifically, the syntax formatting works with Ctrl+Shift+I and saving the file automatically does that.

One last hint: Opening 2 Rust project folders in VSCode at the same time may cause an error message that states Unable to find root directory. Try to avoid that.