Suggestion for misspelled component name

Cargo.toml

@@ -40,6 +40,7 @@ remove_dir_all = "0.5.1"
 same-file = "1"
 scopeguard = "1"
 semver = "0.9"
+strsim = "0.9.1"
 sha2 = "0.8"
 tar = "0.4"
 tempdir = "0.3.4"

src/dist/manifest.rs

@@ -448,4 +448,12 @@ impl Component {
             pkg.to_string()
         }
     }
+    pub fn description_in_manifest(&self) -> String {
+        let pkg = self.short_name_in_manifest();
+        if let Some(ref t) = self.target {
+            format!("'{}' for target '{}'", pkg, t)
+        } else {
+            format!("'{}'", pkg)
+        }
+    }
 }

src/errors.rs

@@ -302,9 +302,9 @@ error_chain! {
             description("toolchain does not support components")
             display("toolchain '{}' does not support components", t)
         }
-        UnknownComponent(t: String, c: String) {
+        UnknownComponent(t: String, c: String, s: String) {
             description("toolchain does not contain component")
-            display("toolchain '{}' does not contain component {}", t, c)
+            display("toolchain '{}' does not contain component {}{}", t, c, s)
         }
         AddingRequiredComponent(t: String, c: String) {
             description("required component cannot be added")

src/toolchain.rs

@@ -604,6 +604,7 @@ impl<'a> Toolchain<'a> {
                     return Err(ErrorKind::UnknownComponent(
                         self.name.to_string(),
                         component.description(&manifest),
+                        self.get_component_suggestion(&component, false),
                     )
                     .into());
                 }
@@ -629,6 +630,50 @@ impl<'a> Toolchain<'a> {
         }
     }
 
+    fn get_component_suggestion(&self, component: &Component, only_instaled: bool) -> String {
+        use strsim::damerau_levenshtein;;
+        // Suggest only for very small differences
+        // High number can result in innacurate suggestions for short queries e.g. `rls`
+        const MAX_DISTANCE: usize = 3;
+
+        let components = self.list_components();
+        if let Ok(components) = components {
+            let min = components
+                .iter()
+                .filter(|c| !only_instaled || c.installed)
+                .map(|c| {
+                    (
+                        damerau_levenshtein(
+                            &c.component.name_in_manifest()[..],
+                            &component.name_in_manifest()[..],
+                        ),
+                        c,
+                    )
+                })
+                .min_by_key(|t| t.0)
+                .expect("There should be always at least one component");
+
+            // If suggestion is too different don't suggest anything
+            if min.0 > MAX_DISTANCE {
+                return String::new();
+            }
+            // If component parts are the same include whole description
+            if min.1.component.short_name_in_manifest() == component.short_name_in_manifest() {
+                return format!(
+                    " - Did you mean {} (targets differ)?",
+                    min.1.component.description_in_manifest()
+                );
+            }
+
+            format!(
+                " - Did you mean '{}'?",
+                min.1.component.short_name_in_manifest()
+            )
+        } else {
+            String::new()
+        }
+    }
+
     pub fn remove_component(&self, mut component: Component) -> Result<()> {
         if !self.exists() {
             return Err(ErrorKind::ToolchainNotInstalled(self.name.to_owned()).into());
@@ -674,6 +719,7 @@ impl<'a> Toolchain<'a> {
                     return Err(ErrorKind::UnknownComponent(
                         self.name.to_string(),
                         component.description(&manifest),
+                        self.get_component_suggestion(&component, true),
                     )
                     .into());
                 }

tests/cli-v2.rs

@@ -920,3 +920,68 @@ fn update_unavailable_force() {
         );
     });
 }
+
+#[test]
+fn add_component_suggest_best_match() {
+    setup(&|config| {
+        expect_ok(config, &["rustup", "default", "nightly"]);
+        expect_err(
+            config,
+            &["rustup", "component", "add", "rustd"],
+            "Did you mean 'rustc'?",
+        );
+    });
+}
+
+#[test]
+fn remove_component_suggest_best_match() {
+    setup(&|config| {
+        expect_ok(config, &["rustup", "default", "nightly"]);
+        expect_err(
+            config,
+            &["rustup", "component", "remove", "rustd"],
+            "Did you mean 'rustc'?",
+        );
+    });
+}
+
+#[test]
+fn add_target_suggest_best_match() {
+    setup(&|config| {
+        expect_ok(config, &["rustup", "default", "nightly"]);
+        expect_err(
+            config,
+            &[
+                "rustup",
+                "target",
+                "add",
+                &format!("{}a", clitools::CROSS_ARCH1)[..],
+            ],
+            &format!(
+                "Did you mean 'rust-std' for target '{}' (targets differ)?",
+                clitools::CROSS_ARCH1
+            )[..],
+        );
+    });
+}
+
+#[test]
+fn remove_target_suggest_best_match() {
+    setup(&|config| {
+        expect_ok(config, &["rustup", "default", "nightly"]);
+        expect_ok(config, &["rustup", "target", "add", clitools::CROSS_ARCH1]);
+        expect_err(
+            config,
+            &[
+                "rustup",
+                "target",
+                "remove",
+                &format!("{}a", clitools::CROSS_ARCH1)[..],
+            ],
+            &format!(
+                "Did you mean 'rust-std' for target '{}' (targets differ)?",
+                clitools::CROSS_ARCH1
+            )[..],
+        );
+    });
+}