feat(cli): add --check flag to rustup update to return exact Exitcode

src/cli/common.rs

@@ -228,6 +228,7 @@ fn show_channel_updates(
 pub(crate) async fn update_all_channels(
     cfg: &Cfg<'_>,
     force_update: bool,
+    check: bool,
 ) -> anyhow::Result<ExitCode> {
     let profile = cfg.get_profile()?;
     let channels = cfg.list_channels()?;
@@ -241,7 +242,9 @@ pub(crate) async fn update_all_channels(
     }))
     .await;
 
-    let mut toolchains = Vec::new();
+    let mut toolchains = Vec::with_capacity(channels_with_manifests.len());
+    let mut has_update_error = false;
+    let mut has_update = false;
     for (desc, distributable, manifest) in channels_with_manifests {
         let result = if force_update || manifest.is_some() {
             let options = DistOptions::new(&[], &[], &desc, profile, force_update, cfg)?
@@ -251,16 +254,22 @@ pub(crate) async fn update_all_channels(
             Ok(UpdateStatus::Unchanged)
         };
 
-        if let Err(e) = &result {
-            error!("{e}");
+        match &result {
+            Ok(UpdateStatus::Updated(_)) | Ok(UpdateStatus::Installed) => has_update = true,
+            Err(e) => {
+                has_update_error = true;
+                error!("{e}");
+            }
+            _ => (),
         }
 
         toolchains.push((desc, result));
     }
 
-    let has_update_error = toolchains.iter().any(|(_, r)| r.is_err());
     let exit_code = if has_update_error {
         ExitCode::FAILURE
+    } else if check && has_update {
+        ExitCode::UPDATES_AVAILABLE
     } else {
         ExitCode::SUCCESS
     };

src/cli/rustup_mode.rs

@@ -202,6 +202,10 @@ enum RustupSubcmd {
         /// Install toolchains that require an emulator. See https://github.com/rust-lang/rustup/wiki/Non-host-toolchains
         #[arg(long)]
         force_non_host: bool,
+
+        /// Indicate update status via exit code
+        #[arg(long)]
+        check: bool,
     },
 
     /// Check for updates to Rust toolchains and rustup
@@ -493,6 +497,10 @@ struct UpdateOpts {
     /// Set the installed toolchain as the default toolchain
     #[arg(long)]
     default: bool,
+
+    /// Indicate update status via exit code
+    #[arg(long)]
+    check: bool,
 }
 
 #[derive(Debug, Default, Args)]
@@ -765,6 +773,7 @@ pub async fn main(
             allow_downgrade,
             force,
             force_non_host,
+            check,
         } => {
             update(
                 cfg,
@@ -774,6 +783,7 @@ pub async fn main(
                     allow_downgrade,
                     force,
                     force_non_host,
+                    check,
                     ..UpdateOpts::default()
                 },
                 false,
@@ -1185,7 +1195,7 @@ async fn update(
         info!("it's active because: {}", source.to_reason());
         exit_code &= self_update_mode.update(should_self_update, &dl_cfg).await?;
     } else {
-        exit_code &= common::update_all_channels(cfg, opts.force).await?;
+        exit_code &= common::update_all_channels(cfg, opts.force, opts.check).await?;
         exit_code &= self_update_mode.update(should_self_update, &dl_cfg).await?;
 
         info!("cleaning up downloads & tmp directories");

tests/suite/cli_rustup.rs

@@ -16,6 +16,57 @@ use rustup::{
     utils::raw,
 };
 
+#[tokio::test]
+async fn update_check_no_updates() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+    cx.config
+        .expect(["rustup", "toolchain", "add", "stable"])
+        .await
+        .is_ok();
+
+    cx.config
+        .expect(["rustup", "update", "--check"])
+        .await
+        .is_ok()
+        .with_stdout(snapbox::str![[r#"
+
+  stable-[HOST_TUPLE] unchanged - 1.1.0 (hash-stable-1.1.0)
+
+
+"#]]);
+}
+
+#[tokio::test]
+async fn update_check_with_partial_updates() {
+    let mut cx = CliTestContext::new(Scenario::None).await;
+
+    {
+        let cx = cx.with_dist_dir(Scenario::ArchivesV2_2015_01_01);
+        cx.config
+            .expect(["rustup", "toolchain", "add", "stable"])
+            .await
+            .is_ok();
+    }
+
+    let cx = cx.with_dist_dir(Scenario::SimpleV2);
+    cx.config
+        .expect(["rustup", "toolchain", "add", "beta"])
+        .await
+        .is_ok();
+
+    cx.config
+        .expect(["rustup", "update", "--check"])
+        .await
+        .has_code(100)
+        .with_stdout(snapbox::str![[r#"
+
+  stable-[HOST_TUPLE] updated - 1.1.0 (hash-stable-1.1.0) (from 1.0.0 (hash-stable-1.0.0))
+  beta-[HOST_TUPLE] unchanged - 1.2.0 (hash-beta-1.2.0)
+
+
+"#]]);
+}
+
 #[tokio::test]
 async fn rustup_stable() {
     let mut cx = CliTestContext::new(Scenario::None).await;