proxies: Make it clear when a binary is not applicable to a given toolchain

Signed-off-by: Daniel Silverstone <dsilvers@digital-scurf.org>

Author: kinnison

src/errors.rs

@@ -312,6 +312,10 @@ error_chain! {
             description("binary is provided by a component which is not available in current toolchain")
             display("the '{}' component which provides the command '{}' is not available for the '{}' toolchain", component, bin, toolchain)
         }
+        BinaryNotProvidedByComponent(component: String, bin: String, toolchain: String) {
+            description("binary should be provided by component but isn't in current toolchain")
+            display("the '{}' binary, normally provided by the '{}' component, is not applicable to the '{}' toolchain", bin, component, toolchain)
+        }
         NeedMetadataUpgrade {
             description("rustup's metadata is out of date. run `rustup self upgrade-data`")
         }

src/lib.rs

@@ -41,8 +41,7 @@ fn component_for_bin(binary: &str) -> Option<&'static str> {
     match binary_prefix {
         "rustc" | "rustdoc" => Some("rustc"),
         "cargo" => Some("cargo"),
-        "rust-lldb" => Some("lldb-preview"),
-        "rust-gdb" => Some("gdb-preview"),
+        "rust-lldb" | "rust-gdb" => Some("rustc"), // These are not always available
         "rls" => Some("rls"),
         "cargo-clippy" => Some("clippy"),
         "clippy-driver" => Some("clippy"),

src/toolchain.rs

@@ -297,6 +297,14 @@ impl<'a> InstalledCommonToolchain<'a> {
                             )
                             .into());
                         }
+                        if component_status.installed {
+                            return Err(ErrorKind::BinaryNotProvidedByComponent(
+                                component_status.component.short_name(&manifest),
+                                binary_lossy,
+                                self.0.name.clone(),
+                            )
+                            .into());
+                        }
                     }
                 }
                 let defaults = self.0.cfg.get_default()?;

tests/cli-misc.rs

@@ -483,6 +483,23 @@ fn run_rls_when_not_installed() {
     });
 }
 
+#[test]
+fn run_rust_lldb_when_not_in_toolchain() {
+    clitools::setup(Scenario::UnavailableRls, &|config| {
+        set_current_dist_date(config, "2015-01-01");
+        expect_ok(config, &["rustup", "default", "nightly"]);
+        expect_err(
+            config,
+            &["rust-lldb", "--version"],
+            &format!(
+                "the 'rust-lldb{}' binary, normally provided by the 'rustc' component, is not applicable to the 'nightly-{}' toolchain",
+                EXE_SUFFIX,
+                this_host_triple(),
+            ),
+        );
+    });
+}
+
 #[test]
 fn rename_rls_before() {
     clitools::setup(Scenario::ArchivesV2, &|config| {

tests/mock/clitools.rs

@@ -133,12 +133,14 @@ pub fn setup(s: Scenario, f: &dyn Fn(&mut Config)) {
     let rustc_path = config.exedir.join(format!("rustc{}", EXE_SUFFIX));
     let cargo_path = config.exedir.join(format!("cargo{}", EXE_SUFFIX));
     let rls_path = config.exedir.join(format!("rls{}", EXE_SUFFIX));
+    let rust_lldb_path = config.exedir.join(format!("rust-lldb{}", EXE_SUFFIX));
 
     copy_binary(&build_path, &rustup_path).unwrap();
     hard_link(&rustup_path, setup_path).unwrap();
     hard_link(&rustup_path, rustc_path).unwrap();
     hard_link(&rustup_path, cargo_path).unwrap();
     hard_link(&rustup_path, rls_path).unwrap();
+    hard_link(&rustup_path, rust_lldb_path).unwrap();
 
     // Make sure the host triple matches the build triple. Otherwise testing a 32-bit build of
     // rustup on a 64-bit machine will fail, because the tests do not have the host detection