fix(rustup-mode)!: don't install toolchain on rustup --version

src/cli/rustup_mode.rs

@@ -547,9 +547,10 @@ pub async fn main(current_dir: PathBuf, process: &Process) -> Result<utils::Exit
             write!(process.stdout().lock(), "{err}")?;
             info!("This is the version for the rustup toolchain manager, not the rustc compiler.");
             let mut cfg = common::set_globals(current_dir, false, true, process)?;
-            match cfg.active_rustc_version().await {
-                Ok(version) => info!("The currently active `rustc` version is `{}`", version),
-                Err(err) => trace!("Wanted to tell you the current rustc version, too, but ran into this error: {}", err),
+            match cfg.active_rustc_version() {
+                Ok(Some(version)) => info!("The currently active `rustc` version is `{version}`"),
+                Ok(None) => info!("No `rustc` is currently active"),
+                Err(err) => trace!("Failed to display the current `rustc` version: {err}"),
             }
             return Ok(utils::ExitCode(0));
         }

src/config.rs

@@ -694,17 +694,16 @@ impl<'a> Cfg<'a> {
     }
 
     #[tracing::instrument(level = "trace")]
-    pub(crate) async fn active_rustc_version(&mut self) -> Result<String> {
+    pub(crate) fn active_rustc_version(&mut self) -> Result<Option<String>> {
         if let Some(t) = self.process.args().find(|x| x.starts_with('+')) {
             trace!("Fetching rustc version from toolchain `{}`", t);
             self.set_toolchain_override(&ResolvableToolchainName::try_from(&t[1..])?);
         }
 
-        Ok(self
-            .find_or_install_active_toolchain()
-            .await?
-            .0
-            .rustc_version())
+        let Some((name, _)) = self.find_active_toolchain()? else {
+            return Ok(None);
+        };
+        Ok(Some(Toolchain::new(self, name)?.rustc_version()))
     }
 
     pub(crate) async fn resolve_toolchain(

tests/suite/cli_misc.rs

@@ -21,21 +21,25 @@ async fn smoke_test() {
 
 #[tokio::test]
 async fn version_mentions_rustc_version_confusion() {
-    let cx = CliTestContext::new(Scenario::SimpleV2).await;
-    let out = cx.config.run("rustup", vec!["--version"], &[]).await;
-    assert!(out.ok);
-    assert!(out
-        .stderr
-        .contains("This is the version for the rustup toolchain manager"));
+    let mut cx = CliTestContext::new(Scenario::SimpleV2).await;
 
-    let out = cx
-        .config
-        .run("rustup", vec!["+nightly", "--version"], &[])
+    cx.config
+        .expect_stderr_ok(
+            &["rustup", "--version"],
+            "This is the version for the rustup toolchain manager",
+        )
+        .await;
+
+    cx.config
+        .expect_ok(&["rustup", "toolchain", "install", "nightly"])
+        .await;
+
+    cx.config
+        .expect_stderr_ok(
+            &["rustup", "+nightly", "--version"],
+            "The currently active `rustc` version is `1.3.0",
+        )
         .await;
-    assert!(out.ok);
-    assert!(out
-        .stderr
-        .contains("The currently active `rustc` version is `1.3.0"));
 }
 
 #[tokio::test]