Add ToolchainComponentsMissing error msg

src/dist/dist.rs

@@ -625,9 +625,7 @@ fn update_from_dist_<'a>(
                     break Err(e);
                 }
 
-                if let ErrorKind::RequestedComponentsUnavailable(components, manifest, ..) =
-                    e.kind()
-                {
+                if let ErrorKind::ToolchainComponentsMissing(components, manifest, ..) = e.kind() {
                     (download.notify_handler)(Notification::SkippingNightlyMissingComponent(
                         &toolchain,
                         current_manifest.as_ref().unwrap_or(manifest),
@@ -777,9 +775,28 @@ fn try_update_from_dist_<'a>(
                 &download.notify_handler,
                 &toolchain.manifest_name(),
                 true,
-            )? {
-                UpdateStatus::Unchanged => Ok(None),
-                UpdateStatus::Changed => Ok(Some(hash)),
+            ) {
+                Ok(status) => match status {
+                    UpdateStatus::Unchanged => Ok(None),
+                    UpdateStatus::Changed => Ok(Some(hash)),
+                },
+                Err(err) => {
+                    return if let ErrorKind::RequestedComponentsUnavailable(
+                        cs,
+                        manifest,
+                        toolchain_str,
+                    ) = err.kind()
+                    {
+                        Err(ErrorKind::ToolchainComponentsMissing(
+                            cs.to_owned(),
+                            manifest.to_owned(),
+                            toolchain_str.to_owned(),
+                        )
+                        .into())
+                    } else {
+                        Err(err)
+                    }
+                }
             };
         }
         Ok(None) => return Ok(None),

src/errors.rs

@@ -299,6 +299,10 @@ error_chain! {
             description("some requested components are unavailable to download")
             display("{}", component_unavailable_msg(&c, &manifest, &toolchain))
         }
+        ToolchainComponentsMissing(c: Vec<Component>, manifest: Manifest,toolchain: String) {
+            description("at least one of the requested components is unavailable to download")
+            display("{}", components_missing_msg(&c,&manifest, &toolchain))
+        }
         UnknownMetadataVersion(v: String) {
             description("unknown metadata version")
             display("unknown metadata version: '{}'", v)
@@ -491,6 +495,54 @@ fn component_unavailable_msg(cs: &[Component], manifest: &Manifest, toolchain: &
     String::from_utf8(buf).unwrap()
 }
 
+fn components_missing_msg(cs: &[Component], manifest: &Manifest, toolchain: &str) -> String {
+    assert!(!cs.is_empty());
+    let mut buf = vec![];
+    let suggestion = format!("    rustup toolchain add {} --profile minimal", toolchain);
+    let nightly_tips = "Sometimes not all components are available in any given nightly. ";
+
+    if cs.len() == 1 {
+        let _ = writeln!(
+            buf,
+            "component {} is unavailable for download for channel '{}'",
+            &cs[0].description(manifest),
+            toolchain,
+        );
+
+        if toolchain.starts_with("nightly") {
+            let _ = write!(buf, "{}", nightly_tips.to_string());
+        }
+
+        let _ = write!(
+            buf,
+            "If you don't need the component, you could try a minimal installation with:\n\n{}",
+            suggestion
+        );
+    } else {
+        let cs_str = cs
+            .iter()
+            .map(|c| c.description(manifest))
+            .collect::<Vec<_>>()
+            .join(", ");
+        let _ = write!(
+            buf,
+            "some components unavailable for download for channel '{}': {}",
+            toolchain, cs_str
+        );
+
+        if toolchain.starts_with("nightly") {
+            let _ = write!(buf, "{}", nightly_tips.to_string());
+        }
+        let _ = write!(
+            buf,
+            "If you don't need the components, you could try a minimal installation with:\n\n{}",
+            suggestion
+        );
+    }
+
+    String::from_utf8(buf).unwrap()
+}
+
 fn install_msg(bin: &str, toolchain: &str, is_default: bool) -> String {
     if Toolchain::is_custom_name(toolchain) {
         return "\nnote: this is a custom toolchain, which cannot use `rustup component add`\n\

tests/cli-v2.rs

@@ -1085,6 +1085,23 @@ fn update_unavailable_std() {
     });
 }
 
+#[test]
+fn add_missing_component_toolchain() {
+    setup(&|config| {
+        make_component_unavailable(config, "rust-std", &this_host_triple());
+        expect_err(
+            config,
+            &["rustup", "toolchain", "add", "nightly"],
+            for_host!(
+                r"component 'rust-std' for target '{0}' is unavailable for download for channel 'nightly'
+Sometimes not all components are available in any given nightly. If you don't need the component, you could try a minimal installation with:
+
+    rustup toolchain add nightly --profile minimal"
+            ),
+        );
+    });
+}
+
 #[test]
 fn update_unavailable_force() {
     setup(&|config| {