Merge pull request #2916 from K900/better-toolchain-error

Provide a more actionable error message when a toolchain is not selected

Author: kinnison

src/bin/rustup-init.rs

@@ -13,8 +13,6 @@
 
 #![recursion_limit = "1024"]
 
-use std::path::PathBuf;
-
 use anyhow::{anyhow, Result};
 use cfg_if::cfg_if;
 use rs_tracing::*;
@@ -62,18 +60,7 @@ fn run_rustup_inner() -> Result<utils::ExitCode> {
     utils::current_dir()?;
     utils::current_exe()?;
 
-    // The name of arg0 determines how the program is going to behave
-    let arg0 = match process().var("RUSTUP_FORCE_ARG0") {
-        Ok(v) => Some(v),
-        Err(_) => process().args().next(),
-    }
-    .map(PathBuf::from);
-    let name = arg0
-        .as_ref()
-        .and_then(|a| a.file_stem())
-        .and_then(std::ffi::OsStr::to_str);
-
-    match name {
+    match process().name().as_deref() {
         Some("rustup") => rustup_mode::main(),
         Some(n) if n.starts_with("rustup-setup") || n.starts_with("rustup-init") => {
             // NB: The above check is only for the prefix of the file

src/currentprocess.rs

@@ -87,6 +87,8 @@ pub trait CurrentProcess:
     + Debug
 {
     fn clone_boxed(&self) -> Box<dyn CurrentProcess>;
+
+    fn name(&self) -> Option<String>;
 }
 
 // Machinery for Cloning boxes
@@ -107,6 +109,19 @@ where
     fn clone_boxed(&self) -> Box<dyn CurrentProcess + 'static> {
         Box::new(T::clone(self))
     }
+
+    fn name(&self) -> Option<String> {
+        let arg0 = match self.var("RUSTUP_FORCE_ARG0") {
+            Ok(v) => Some(v),
+            Err(_) => self.args().next(),
+        }
+        .map(PathBuf::from);
+
+        arg0.as_ref()
+            .and_then(|a| a.file_stem())
+            .and_then(std::ffi::OsStr::to_str)
+            .map(String::from)
+    }
 }
 
 impl Clone for Box<dyn CurrentProcess + 'static> {

src/errors.rs

@@ -8,6 +8,7 @@ use std::path::PathBuf;
 use thiserror::Error as ThisError;
 use url::Url;
 
+use crate::currentprocess::process;
 use crate::dist::manifest::{Component, Manifest};
 
 const TOOLSTATE_MSG: &str =
@@ -88,7 +89,11 @@ pub enum RustupError {
     ToolchainNotInstallable(String),
     #[error("toolchain '{0}' is not installed")]
     ToolchainNotInstalled(String),
-    #[error("no override and no default toolchain set")]
+    #[error(
+        "rustup could not choose a version of {} to run, because one wasn't specified explicitly, and no default is configured.\n{}",
+        process().name().unwrap_or_else(|| "Rust".into()),
+        "help: run 'rustup default stable' to download the latest stable release of Rust and set it as your default toolchain."
+    )]
     ToolchainNotSelected,
     #[error("toolchain '{}' does not contain component {}{}{}", .name, .component, if let Some(suggestion) = .suggestion {
         format!("; did you mean '{}'?", suggestion)

tests/cli-exact.rs

@@ -599,7 +599,9 @@ fn default_none() {
             config,
             &["rustc", "--version"],
             "",
-            "error: no override and no default toolchain set\n",
+            "error: rustup could not choose a version of rustc to run, because one wasn't specified explicitly, and no default is configured.
+help: run 'rustup default stable' to download the latest stable release of Rust and set it as your default toolchain.
+",
         );
     })
 }

tests/cli-rustup.rs

@@ -2179,7 +2179,7 @@ fn rust_toolchain_toml() {
         expect_err(
             config,
             &["rustc", "--version"],
-            "no override and no default toolchain set",
+            "rustup could not choose a version of rustc to run",
         );
 
         let cwd = config.current_dir();

tests/cli-v1.rs

@@ -22,7 +22,7 @@ fn rustc_no_default_toolchain() {
         expect_err(
             config,
             &["rustc"],
-            "no override and no default toolchain set",
+            "rustup could not choose a version of rustc to run",
         );
     });
 }
@@ -305,7 +305,7 @@ fn remove_override_no_default() {
             expect_err(
                 config,
                 &["rustc"],
-                "no override and no default toolchain set",
+                "rustup could not choose a version of rustc to run",
             );
         });
     });

tests/cli-v2.rs

@@ -30,7 +30,7 @@ fn rustc_no_default_toolchain() {
         expect_err(
             config,
             &["rustc"],
-            "no override and no default toolchain set",
+            "rustup could not choose a version of rustc to run",
         );
     });
 }
@@ -477,7 +477,7 @@ fn remove_override_no_default() {
             expect_err(
                 config,
                 &["rustc"],
-                "no override and no default toolchain set",
+                "rustup could not choose a version of rustc to run",
             );
         });
     });