feat(config)!: use unqualified names for default_toolchain

src/cli/rustup_mode.rs

@@ -887,13 +887,13 @@ async fn default_(
                 cfg.set_default(Some(&toolchain_name.into()))?;
             }
             MaybeResolvableToolchainName::Some(ResolvableToolchainName::Official(toolchain)) => {
-                let desc = toolchain.resolve(&cfg.default_host_tuple()?)?;
+                let desc = toolchain.clone().resolve(&cfg.default_host_tuple()?)?;
                 let status = cfg
                     .ensure_installed(&desc, vec![], vec![], None, force_non_host, true)
                     .await?
                     .status;
 
-                cfg.set_default(Some(&desc.clone().into()))?;
+                cfg.set_default(Some(&toolchain.into()))?;
 
                 writeln!(cfg.process.stdout().lock())?;
 
@@ -1091,7 +1091,7 @@ async fn update(
                     force_non_host,
                 )?;
             }
-            let desc = name.resolve(&cfg.default_host_tuple()?)?;
+            let desc = name.clone().resolve(&cfg.default_host_tuple()?)?;
 
             let components = opts.component.iter().map(|s| &**s).collect::<Vec<_>>();
             let targets = opts.target.iter().map(|s| &**s).collect::<Vec<_>>();
@@ -1134,7 +1134,7 @@ async fn update(
             if opts.default
                 || (cfg.get_default()?.is_none() && matches!(status, UpdateStatus::Installed))
             {
-                cfg.set_default(Some(&desc.into()))?;
+                cfg.set_default(Some(&name.into()))?;
             }
         }
         exit_code &= self_update_mode.update(should_self_update, &dl_cfg).await?;

src/cli/self_update.rs

@@ -69,7 +69,6 @@ use crate::{
     process::Process,
     toolchain::{
         DistributableToolchain, MaybeOfficialToolchainName, ResolvableToolchainName, Toolchain,
-        ToolchainName,
     },
     utils::{self, ExitCode},
 };
@@ -252,7 +251,8 @@ impl InstallOpts<'_> {
 
         let (components, targets) = (self.components, self.targets);
         let toolchain = self.select_toolchain(cfg)?;
-        if let Some(desc) = toolchain {
+        if let Some(partial_desc) = toolchain {
+            let desc = partial_desc.clone().resolve(&cfg.default_host_tuple()?)?;
             let options =
                 DistOptions::new(components, targets, &desc, cfg.get_profile()?, true, cfg)?;
             let status = if Toolchain::exists(cfg, &desc.clone().into())? {
@@ -272,7 +272,7 @@ impl InstallOpts<'_> {
 
             check_proxy_sanity(cfg.process, components, &desc)?;
 
-            cfg.set_default(Some(&desc.clone().into()))?;
+            cfg.set_default(Some(&partial_desc.into()))?;
             writeln!(cfg.process.stdout().lock())?;
             common::show_channel_update(cfg, PackageUpdate::Toolchain(desc), Ok(status))?;
         }
@@ -284,7 +284,7 @@ impl InstallOpts<'_> {
     /// This function first initializes the default profile and default host tuple in the
     /// configuration, then returns the toolchain that should be installed, or `None` if none is
     /// specified by the user.
-    fn select_toolchain(self, cfg: &mut Cfg<'_>) -> Result<Option<ToolchainDesc>> {
+    fn select_toolchain(self, cfg: &mut Cfg<'_>) -> Result<Option<PartialToolchainDesc>> {
         let Self {
             default_host_tuple,
             default_toolchain,
@@ -342,18 +342,14 @@ impl InstallOpts<'_> {
                         MaybeOfficialToolchainName::None => unreachable!(),
                         MaybeOfficialToolchainName::Some(n) => n,
                     };
-                    Some(toolchain_name.resolve(&cfg.default_host_tuple()?)?)
+                    Some(toolchain_name)
                 }
-                None => match cfg.get_default()? {
+                None => match cfg.get_default_resolvable()? {
                     // Default is installable
-                    Some(ToolchainName::Official(t)) => Some(t),
+                    Some(ResolvableToolchainName::Official(t)) => Some(t),
                     // Default is custom, presumably from a prior install. Do nothing.
-                    Some(ToolchainName::Custom(_)) => None,
-                    None => Some(
-                        "stable"
-                            .parse::<PartialToolchainDesc>()?
-                            .resolve(&cfg.default_host_tuple()?)?,
-                    ),
+                    Some(ResolvableToolchainName::Custom(_)) => None,
+                    None => Some(PartialToolchainDesc::from_str("stable")?),
                 },
             })
         } else {
@@ -1378,11 +1374,7 @@ mod tests {
             };
 
             assert_eq!(
-                "stable"
-                    .parse::<PartialToolchainDesc>()
-                    .unwrap()
-                    .resolve(&cfg.default_host_tuple().unwrap())
-                    .unwrap(),
+                "stable".parse::<PartialToolchainDesc>().unwrap(),
                 opts.select_toolchain(&mut cfg)
                     .unwrap() // result
                     .unwrap() // option

src/config.rs

@@ -384,7 +384,7 @@ impl<'a> Cfg<'a> {
         Ok(cfg)
     }
 
-    pub(crate) fn set_default(&self, toolchain: Option<&ToolchainName>) -> Result<()> {
+    pub(crate) fn set_default(&self, toolchain: Option<&ResolvableToolchainName>) -> Result<()> {
         self.settings_file.with_mut(|s| {
             s.default_toolchain = toolchain.map(|t| t.to_string());
             Ok(())
@@ -900,10 +900,24 @@ impl<'a> Cfg<'a> {
         })
     }
 
-    /// Get the configured default toolchain.
-    /// If none is configured, returns None
-    /// If a bad toolchain name is configured, errors.
+    /// Gets the configured default toolchain name in its resolved form, if any.
+    ///
+    /// This is essentially [`Cfg::get_default_resolvable()`] with an extra resolution step.
     pub(crate) fn get_default(&self) -> Result<Option<ToolchainName>> {
+        let Some(toolchain) = self.get_default_resolvable()? else {
+            return Ok(None);
+        };
+        Ok(Some(toolchain.resolve(&self.default_host_tuple()?)?))
+    }
+
+    /// Gets the configured default toolchain name in its unresolved form, if any.
+    ///
+    /// # Errors
+    ///
+    /// This function returns an error if:
+    /// - The configuration file is invalid.
+    /// - The configuration file contains an illegal default toolchain name.
+    pub(crate) fn get_default_resolvable(&self) -> Result<Option<ResolvableToolchainName>> {
         let user_opt = self.settings_file.with(|s| Ok(s.default_toolchain.clone()));
         let toolchain_maybe_str = if let Some(fallback_settings) = &self.fallback_settings {
             match user_opt {
@@ -913,11 +927,10 @@ impl<'a> Cfg<'a> {
         } else {
             user_opt
         }?;
-        toolchain_maybe_str
-            .map(|s| ResolvableToolchainName::from_str(&s))
-            .transpose()?
-            .map(|t| t.resolve(&self.default_host_tuple()?))
-            .transpose()
+        let Some(toolchain) = &toolchain_maybe_str else {
+            return Ok(None);
+        };
+        Ok(Some(ResolvableToolchainName::from_str(toolchain)?))
     }
 
     /// List all the installed toolchains: that is paths in the toolchain dir

src/toolchain/names.rs

@@ -296,6 +296,18 @@ impl ResolvableLocalToolchainName {
     }
 }
 
+impl From<PartialToolchainDesc> for ResolvableToolchainName {
+    fn from(value: PartialToolchainDesc) -> Self {
+        Self::Official(value)
+    }
+}
+
+impl From<CustomToolchainName> for ResolvableToolchainName {
+    fn from(value: CustomToolchainName) -> Self {
+        Self::Custom(value)
+    }
+}
+
 impl FromStr for ResolvableLocalToolchainName {
     type Err = InvalidName;
 

tests/suite/cli_exact.rs

@@ -23,7 +23,7 @@ async fn update_once() {
 info: syncing channel updates for nightly-[HOST_TUPLE]
 info: latest update on 2015-01-02 for version 1.3.0 (hash-nightly-2)
 info: downloading 4 components
-info: default toolchain set to nightly-[HOST_TUPLE]
+info: default toolchain set to nightly
 
 "#]]);
     cx.config
@@ -322,7 +322,7 @@ async fn default() {
 info: syncing channel updates for nightly-[HOST_TUPLE]
 info: latest update on 2015-01-02 for version 1.3.0 (hash-nightly-2)
 info: downloading 4 components
-info: default toolchain set to nightly-[HOST_TUPLE]
+info: default toolchain set to nightly
 
 "#]]);
     cx.config

tests/suite/cli_inst_interactive.rs

@@ -4,7 +4,9 @@ use std::env::consts::EXE_SUFFIX;
 use std::io::Write;
 use std::process::Stdio;
 
-use rustup::test::{Assert, CliTestContext, Config, SanitizedOutput, Scenario, this_host_tuple};
+use rustup::test::{
+    Assert, CROSS_ARCH1, CliTestContext, Config, SanitizedOutput, Scenario, this_host_tuple,
+};
 #[cfg(windows)]
 use rustup::test::{RegistryGuard, USER_PATH};
 use rustup::utils::raw;
@@ -685,3 +687,68 @@ warn: many Rust crates require a system C toolchain to build
 ...
 "#]]);
 }
+
+// https://github.com/rust-lang/rustup/issues/3651#issuecomment-5058868560
+#[tokio::test]
+async fn install_defaults_to_default_host() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+    let redactions = [("[RUSTUP_DIR]", &cx.config.rustupdir.to_string())];
+
+    cx.config
+        .expect([
+            "rustup-init",
+            "-y",
+            "--no-modify-path",
+            "--default-toolchain=beta",
+        ])
+        .await
+        .is_ok();
+
+    cx.config
+        .expect(["rustup", "show"])
+        .await
+        .extend_redactions(redactions)
+        .is_ok()
+        .with_stdout(snapbox::str![[r#"
+Default host: [HOST_TUPLE]
+rustup home:  [RUSTUP_DIR]
+
+installed toolchains
+--------------------
+beta-[HOST_TUPLE] (active, default)
+
+active toolchain
+----------------
+name: beta-[HOST_TUPLE]
+active because: it's the default toolchain
+installed targets:
+  [HOST_TUPLE]
+
+"#]]);
+
+    cx.config
+        .expect(["rustup", "set", "default-host", CROSS_ARCH1])
+        .await
+        .is_ok()
+        .with_stdout(snapbox::str![[r#""#]]);
+
+    cx.config
+        .expect_with_env(["rustup", "show"], [("RUSTUP_AUTO_INSTALL", "0")])
+        .await
+        .extend_redactions(redactions)
+        .is_ok()
+        .with_stdout(snapbox::str![[r#"
+Default host: [CROSS_ARCH_I]
+rustup home:  [RUSTUP_DIR]
+
+installed toolchains
+--------------------
+beta-[HOST_TUPLE]
+
+active toolchain
+----------------
+name: beta-[CROSS_ARCH_I]
+active because: it's the default toolchain
+
+"#]]);
+}

tests/suite/cli_rustup.rs

@@ -290,7 +290,7 @@ async fn default() {
 info: syncing channel updates for nightly-[HOST_TUPLE]
 info: latest update on 2015-01-02 for version 1.3.0 (hash-nightly-2)
 info: downloading 4 components
-info: default toolchain set to nightly-[HOST_TUPLE]
+info: default toolchain set to nightly
 
 "#]])
         .is_ok();
@@ -327,7 +327,7 @@ async fn default_override() {
         .await
         .with_stderr(snapbox::str![[r#"
 info: using existing install for stable-[HOST_TUPLE]
-info: default toolchain set to stable-[HOST_TUPLE]
+info: default toolchain set to stable
 info: note that the toolchain 'nightly-[HOST_TUPLE]' is currently in use (directory override for '[..]')
 
 "#]])
@@ -4032,7 +4032,7 @@ async fn custom_toolchain_with_components_toolchains_profile_does_not_err() {
 info: syncing channel updates for nightly-[HOST_TUPLE]
 info: latest update on 2015-01-02 for version 1.3.0 (hash-nightly-2)
 info: downloading 2 components
-info: default toolchain set to nightly-[HOST_TUPLE]
+info: default toolchain set to nightly
 
 "#]])
         .is_ok();
@@ -4264,3 +4264,63 @@ fn nightly_manifest_path(cx: &CliTestContext) -> PathBuf {
         .join("rustlib")
         .join("multirust-channel-manifest.toml")
 }
+
+// https://github.com/rust-lang/rustup/issues/3651#issuecomment-5058814392
+#[tokio::test]
+async fn default_stores_unqualified_toolchains() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+    let redactions = [("[RUSTUP_DIR]", &cx.config.rustupdir.to_string())];
+
+    cx.config
+        .expect(["rustup", "default", "beta"])
+        .await
+        .is_ok();
+
+    cx.config
+        .expect(["rustup", "show"])
+        .await
+        .extend_redactions(redactions)
+        .is_ok()
+        .with_stdout(snapbox::str![[r#"
+Default host: [HOST_TUPLE]
+rustup home:  [RUSTUP_DIR]
+
+installed toolchains
+--------------------
+beta-[HOST_TUPLE] (active, default)
+
+active toolchain
+----------------
+name: beta-[HOST_TUPLE]
+active because: it's the default toolchain
+installed targets:
+  [HOST_TUPLE]
+
+"#]]);
+
+    cx.config
+        .expect(["rustup", "set", "default-host", CROSS_ARCH1])
+        .await
+        .is_ok()
+        .with_stdout(snapbox::str![[r#""#]]);
+
+    cx.config
+        .expect_with_env(["rustup", "show"], [("RUSTUP_AUTO_INSTALL", "0")])
+        .await
+        .extend_redactions(redactions)
+        .is_ok()
+        .with_stdout(snapbox::str![[r#"
+Default host: [CROSS_ARCH_I]
+rustup home:  [RUSTUP_DIR]
+
+installed toolchains
+--------------------
+beta-[HOST_TUPLE]
+
+active toolchain
+----------------
+name: beta-[CROSS_ARCH_I]
+active because: it's the default toolchain
+
+"#]]);
+}