Merge #4329

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.) https://github.com/rust-analyzer/rust-analyzer/blob/a4778ddb7a00f552a8e653bbf56ae9fd69cfe1d3/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 <[email protected]>
Co-authored-by: veetaha <[email protected]>

1 files changed, 12 insertions, 4 deletions

diff --git a/crates/ra_project_model/src/sysroot.rs b/crates/ra_project_model/src/sysroot.rs
index 55ff5ad80..11c26ad89 100644
--- a/crates/ra_project_model/src/sysroot.rs
+++ b/crates/ra_project_model/src/sysroot.rs
@@ -8,6 +8,7 @@ use std::{
 };
 
 use ra_arena::{Arena, Idx};
+use ra_env::get_path_for_executable;
 
 #[derive(Default, Debug, Clone)]
 pub struct Sysroot {
@@ -88,9 +89,14 @@ fn create_command_text(program: &str, args: &[&str]) -> String {
     format!("{} {}", program, args.join(" "))
 }
 
-fn run_command_in_cargo_dir(cargo_toml: &Path, program: &str, args: &[&str]) -> Result<Output> {
+fn run_command_in_cargo_dir(
+    cargo_toml: impl AsRef<Path>,
+    program: impl AsRef<Path>,
+    args: &[&str],
+) -> Result<Output> {
+    let program = program.as_ref().as_os_str().to_str().expect("Invalid Unicode in path");
     let output = Command::new(program)
-        .current_dir(cargo_toml.parent().unwrap())
+        .current_dir(cargo_toml.as_ref().parent().unwrap())
         .args(args)
         .output()
         .context(format!("{} failed", create_command_text(program, args)))?;
@@ -114,13 +120,15 @@ fn get_or_install_rust_src(cargo_toml: &Path) -> Result<PathBuf> {
     if let Ok(path) = env::var("RUST_SRC_PATH") {
         return Ok(path.into());
     }
-    let rustc_output = run_command_in_cargo_dir(cargo_toml, "rustc", &["--print", "sysroot"])?;
+    let rustc = get_path_for_executable("rustc")?;
+    let rustc_output = run_command_in_cargo_dir(cargo_toml, &rustc, &["--print", "sysroot"])?;
     let stdout = String::from_utf8(rustc_output.stdout)?;
     let sysroot_path = Path::new(stdout.trim());
     let src_path = sysroot_path.join("lib/rustlib/src/rust/src");
 
     if !src_path.exists() {
-        run_command_in_cargo_dir(cargo_toml, "rustup", &["component", "add", "rust-src"])?;
+        let rustup = get_path_for_executable("rustup")?;
+        run_command_in_cargo_dir(cargo_toml, &rustup, &["component", "add", "rust-src"])?;
     }
     if !src_path.exists() {
         bail!(