Parts of RA re-execute itself, making it unsuitable for use as a library

[aidanhs]

Specifically https://github.com/rust-analyzer/rust-analyzer/blob/ed4b312fa777ebb39ba1348fe3df574c441a485e/crates/rust-analyzer/src/cli/load_cargo.rs#L44-L63

I was surprised, because the comment says "this function is used by external tools that use rust-analyzer as a library" - but it then promptly re-executes RA.

I was able to work around via environment variables in my binary code, but I couldn't find this gotcha documented anywhere (in particular, in ARCHITECTURE.md).

[flodiebold]

I suspect the consumers using this function don't enable proc macros. IMO the rust-analyzer crate is not really intended as a public interface. But ping @matklad

[flodiebold]

Yeah: regexident/cargo-modules@5c71c97

[matklad]

Yeah, in general we don't give any guarantees about our API, up to potentially eating one of your socks.

That being said, it's the wrong API to just self-execute from the guts on the library. std::env::current_exe() should every be only called in main, and everything else should just get an ProcMacroServer as an argument.