4329: Look for `cargo`, `rustc`, and `rustup` in standard installation path r=matklad a=cdisselkoen
Discussed in #3118. This is approximately a 90% fix for the issue described there.
This PR creates a new crate `ra_env` with a function `get_path_for_executable()`; see docs there. `get_path_for_executable()` improves and generalizes the function `cargo_binary()` which was previously duplicated in the `ra_project_model` and `ra_flycheck` crates. (Both of those crates now depend on the new `ra_env` crate.) The new function checks (e.g.) `$CARGO` and `$PATH`, but also falls back on `~/.cargo/bin` manually before erroring out. This should allow most users to not have to worry about setting the `$CARGO` or `$PATH` variables for VSCode, which can be difficult e.g. on macOS as discussed in #3118.
I've attempted to replace all calls to `cargo`, `rustc`, and `rustup` in rust-analyzer with appropriate invocations of `get_path_for_executable()`; I don't think I've missed any in Rust code, but there is at least one invocation in TypeScript code which I haven't fixed. (I'm not sure whether it's affected by the same problem or not.) a4778ddb7a/editors/code/src/cargo.ts (L79)
I'm sure this PR could be improved a bunch, so I'm happy to take feedback/suggestions on how to solve this problem better, or just bikeshedding variable/function/crate names etc.
cc @Veetaha
Fixes#3118.
Co-authored-by: Craig Disselkoen <craigdissel@gmail.com>
Co-authored-by: veetaha <veetaha2@gmail.com>
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