Add RUSTUP_TOOLCHAIN_DIR

src/toolchain.rs

@@ -401,6 +401,7 @@ impl<'a> InstalledCommonToolchain<'a> {
 
         cmd.env("RUSTUP_TOOLCHAIN", &self.0.name);
         cmd.env("RUSTUP_HOME", &self.0.cfg.rustup_dir);
+        cmd.env("RUSTUP_TOOLCHAIN_DIR", &self.0.path);
     }
 
     fn set_ldpath(&self, cmd: &mut Command) {

tests/cli-rustup.rs

@@ -4,7 +4,7 @@ pub mod mock;
 
 use std::env::consts::EXE_SUFFIX;
 use std::fs;
-use std::path::{PathBuf, MAIN_SEPARATOR};
+use std::path::{Path, PathBuf, MAIN_SEPARATOR};
 
 use rustup::for_host;
 use rustup::test::this_host_triple;
@@ -2252,3 +2252,19 @@ fn warn_on_duplicate_rust_toolchain_file() {
         );
     });
 }
+
+/// Checks that the RUSTUP_TOOLCHAIN_DIR is set.
+#[test]
+fn toolchain_dir_env() {
+    setup(&|config| {
+        expect_ok(config, &["rustup", "default", "nightly"]);
+        let output = clitools::run(config, "rustup", &["which", "rustc"], &[]);
+        let real_mock_rustc = Path::new(output.stdout.trim());
+        let toolchain_dir = real_mock_rustc.parent().unwrap().parent().unwrap();
+        expect_stderr_ok(
+            config,
+            &["rustc", "--echo-env", "RUSTUP_TOOLCHAIN_DIR"],
+            toolchain_dir.to_str().unwrap(),
+        );
+    });
+}

tests/mock/mock_bin_src.rs

@@ -71,6 +71,11 @@ fn main() {
             let mut out = io::stderr();
             writeln!(out, "{}", std::env::var("PATH").unwrap()).unwrap();
         }
+        Some("--echo-env") => {
+            let mut out = io::stderr();
+            let var = args.next().unwrap();
+            writeln!(out, "{}", std::env::var(var).unwrap_or_default()).unwrap();
+        }
         _ => panic!("bad mock proxy commandline"),
     }
 }