feat: Automatically detect rust library source file map

[vsrs]

This PR adds a new possible rust-analyzer.debug.sourceFileMap value:

{
    "rust-analyzer.debug.sourceFileMap": "auto"
}

I did not make it the default because it uses two shell calls (rustc --print sysroot and rustc -V -v). First one can be slow (rust-lang/rustup#783)

Fixes #8619

[EFanZh]

I also found that there are paths start with /cargo/, Like /cargo/registry/src/github.com-1ecc6299db9ec823/. Is it a good idea to map it to the user .cargo cache? Like ~/.cargo/?

Also, the "auto" value prevents user from adding custom source mappings. How about using a separate configuration property for this?

[vsrs]

I also found that there are paths start with /cargo/, Like /cargo/registry/src/github.com-1ecc6299db9ec823/. Is it a good idea to map it to the user .cargo cache? Like ~/.cargo/?

I suppose, these are dependencies, and all the necessary information should be in the compiled executable (or pdb on windows).

Also, the "auto" value prevents user from adding custom source mappings.

This is intentional. Conflicts are possible if you automatically add a value to the existing source map. And it's easy to forget and then spend a lot of time trying to figure out the reason. Trust me, I've done that before :)

[EFanZh]

The /cargo dependencies are likely to be dependencies used by standard libraries.

For example, this command on my PC:

nm -Cl ~/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/libstd-b1047a2788193be4.so | grep /cargo

shows many symbols that have paths start with /cargo/. This library is distributed with the Rust toolchain.

[matklad]

bors d+

The code looks OK to me, but I don't really understand the debugging domain at all )

[bors]

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[vsrs]

bors r+

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)