feat(errors): suggest another toolchain on component removal

src/errors.rs

@@ -82,6 +82,66 @@ impl fmt::Display for TargetSuggestion {
     }
 }
 
+#[derive(Debug, Clone)]
+pub enum ComponentSuggestion {
+    Toolchain { name: String, component: String },
+    Component(String),
+}
+
+impl ComponentSuggestion {
+    pub(crate) fn for_removal(
+        desc: &ChannelToolchainName,
+        component: &Component,
+        config: &DistConfig,
+        manifest: &Manifest,
+        cfg: &Cfg<'_>,
+    ) -> Option<Self> {
+        let Ok(toolchains) = cfg.list_toolchains(true) else {
+            return component_suggestion(desc, component, config, manifest, true)
+                .map(Self::Component);
+        };
+
+        let names = [component.name(), component.wildcard().name()];
+        for toolchain_name in toolchains {
+            if let ToolchainName::Channel(toolchain_desc) = &toolchain_name
+                && toolchain_desc == desc
+            {
+                continue;
+            }
+
+            let Ok(toolchain) = Toolchain::new(cfg, toolchain_name.clone().into()) else {
+                continue;
+            };
+            let Ok(installed_components) = toolchain.installed_components() else {
+                continue;
+            };
+
+            if installed_components
+                .iter()
+                .any(|c| names.iter().any(|n| n == c.name()))
+            {
+                return Some(Self::Toolchain {
+                    name: toolchain_name.to_string(),
+                    component: manifest.short_name(component).to_string(),
+                });
+            }
+        }
+
+        component_suggestion(desc, component, config, manifest, true).map(Self::Component)
+    }
+}
+
+impl fmt::Display for ComponentSuggestion {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Toolchain { name, component } => {
+                write!(f, "try `rustup +{name} component remove {component}`")
+            }
+            Self::Component(name) => write!(f, "did you mean '{name}'?"),
+        }
+    }
+}
+
 pub(crate) fn component_suggestion(
     desc: &ChannelToolchainName,
     component: &Component,
@@ -157,7 +217,7 @@ pub struct OperationError(pub anyhow::Error);
 pub struct UnknownComponentInfo {
     pub name: String,
     pub description: String,
-    pub suggestion: Option<String>,
+    pub suggestion: Option<ComponentSuggestion>,
 }
 
 #[derive(ThisError, Debug)]
@@ -418,7 +478,7 @@ fn unknown_components_msg(
             );
 
             if let Some(suggestion) = &component.suggestion {
-                let _ = write!(buf, "\nhelp: did you mean '{suggestion}'?");
+                let _ = write!(buf, "\nhelp: {suggestion}");
             }
 
             if component.description.contains("rust-std") {
@@ -442,7 +502,7 @@ fn unknown_components_msg(
                 let _ = writeln!(buf, "  - '{}'", component.name);
 
                 if let Some(suggestion) = &component.suggestion {
-                    let _ = writeln!(buf, "    help: did you mean '{suggestion}'?");
+                    let _ = writeln!(buf, "    help: {suggestion}");
                 }
             }
         }

src/toolchain/distributable.rs

@@ -21,7 +21,7 @@ use crate::{
         manifestation::{Changes, Manifestation},
         prefix::InstallPrefix,
     },
-    errors::{TargetSuggestion, UnknownComponentInfo, component_suggestion},
+    errors::{ComponentSuggestion, TargetSuggestion, UnknownComponentInfo, component_suggestion},
     install::InstallMethod,
 };
 
@@ -113,7 +113,7 @@ impl<'a> DistributableToolchain<'a> {
                     components: vec![UnknownComponentInfo {
                         name: manifest.short_name(&component).to_string(),
                         description: manifest.description(&component),
-                        suggestion,
+                        suggestion: suggestion.map(ComponentSuggestion::Component),
                     }],
                 }
                 .into());
@@ -361,7 +361,13 @@ impl<'a> DistributableToolchain<'a> {
                 .into());
             }
 
-            let suggestion = component_suggestion(&self.desc, &component, &config, &manifest, true);
+            let suggestion = ComponentSuggestion::for_removal(
+                &self.desc,
+                &component,
+                &config,
+                &manifest,
+                self.toolchain.cfg,
+            );
 
             unknown_components.push(UnknownComponentInfo {
                 name: manifest.short_name(&component).to_string(),

tests/suite/cli_v2.rs

@@ -1862,6 +1862,67 @@ error: toolchain 'stable-[HOST_TUPLE]' does not have target '[CROSS_ARCH_I]' ins
         .is_err();
 }
 
+#[tokio::test]
+async fn remove_component_not_installed_with_suggestion() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+    cx.config
+        .expect(["rustup", "toolchain", "install", "stable"])
+        .await
+        .is_ok();
+    cx.config
+        .expect(["rustup", "toolchain", "install", "nightly"])
+        .await
+        .is_ok();
+    cx.config
+        .expect(["rustup", "default", "stable"])
+        .await
+        .is_ok();
+    cx.config
+        .expect([
+            "rustup",
+            "component",
+            "add",
+            "rust-analysis",
+            "--toolchain=nightly",
+        ])
+        .await
+        .is_ok();
+    cx.config
+        .expect(["rustup", "component", "remove", "rust-analysis"])
+        .await
+        .with_stderr(snapbox::str![[r#"
+error: toolchain 'stable-[HOST_TUPLE]' does not contain component 'rust-analysis' for target '[HOST_TUPLE]'
+help: try `rustup +nightly-[HOST_TUPLE] component remove rust-analysis`
+
+"#]])
+        .is_err();
+}
+
+#[tokio::test]
+async fn remove_component_not_installed_no_alternative() {
+    let cx = CliTestContext::new(Scenario::SimpleV2).await;
+    cx.config
+        .expect(["rustup", "toolchain", "install", "stable"])
+        .await
+        .is_ok();
+    cx.config
+        .expect(["rustup", "toolchain", "install", "nightly"])
+        .await
+        .is_ok();
+    cx.config
+        .expect(["rustup", "default", "stable"])
+        .await
+        .is_ok();
+    cx.config
+        .expect(["rustup", "component", "remove", "rust-analysis"])
+        .await
+        .with_stderr(snapbox::str![[r#"
+error: toolchain 'stable-[HOST_TUPLE]' does not contain component 'rust-analysis' for target '[HOST_TUPLE]'
+
+"#]])
+        .is_err();
+}
+
 #[tokio::test]
 async fn remove_target_no_toolchain() {
     let cx = CliTestContext::new(Scenario::SimpleV2).await;