Print help when a ValueValidation error occurs

Signed-off-by: hi-rustin <[email protected]>

Author: 0xPoe

src/cli/rustup_mode.rs

@@ -30,6 +30,10 @@ use crate::utils::utils;
 use crate::Notification;
 use crate::{command, Cfg, ComponentStatus, Toolchain};
 
+const TOOLCHAIN_OVERRIDE_ERROR: &str =
+    "To override the toolchain using the 'rustup +toolchain' syntax, \
+                        make sure to prefix the toolchain override with a '+'";
+
 fn handle_epipe(res: Result<utils::ExitCode>) -> Result<utils::ExitCode> {
     match res {
         Err(e) => {
@@ -110,6 +114,15 @@ pub fn main() -> Result<utils::ExitCode> {
                 write!(process().stdout().lock(), "{err}")?;
                 return Ok(utils::ExitCode(1));
             }
+            if err.kind() == ValueValidation {
+                if err.to_string().contains(TOOLCHAIN_OVERRIDE_ERROR) {
+                    err!("{TOOLCHAIN_OVERRIDE_ERROR}\n");
+                    cli().print_help()?;
+                } else {
+                    write!(process().stdout().lock(), "{err}")?;
+                }
+                return Ok(utils::ExitCode(1));
+            }
             Err(err)
         }
     }?;
@@ -245,7 +258,7 @@ pub(crate) fn cli() -> Command<'static> {
                     if s.starts_with('+') {
                         Ok(s.to_owned())
                     } else {
-                        Err("Toolchain overrides must begin with '+'".to_owned())
+                        Err(TOOLCHAIN_OVERRIDE_ERROR.to_owned())
                     }
                 }),
         )

tests/suite/cli-ui/rustup/rustup_unknown_arg_stdout.toml

@@ -0,0 +1,51 @@
+bin.name = "rustup"
+args = ["random"]
+status.code = 1
+stdout = """
+rustup [..]
+The Rust toolchain installer
+
+USAGE:
+    rustup[EXE] [OPTIONS] [+toolchain] <SUBCOMMAND>
+
+ARGS:
+    <+toolchain>    release channel (e.g. +stable) or custom toolchain to set override
+
+OPTIONS:
+    -v, --verbose    Enable verbose output
+    -q, --quiet      Disable progress output
+    -h, --help       Print help information
+    -V, --version    Print version information
+
+SUBCOMMANDS:
+    show           Show the active and installed toolchains or profiles
+    update         Update Rust toolchains and rustup
+    check          Check for updates to Rust toolchains and rustup
+    default        Set the default toolchain
+    toolchain      Modify or query the installed toolchains
+    target         Modify a toolchain's supported targets
+    component      Modify a toolchain's installed components
+    override       Modify directory toolchain overrides
+    run            Run a command with an environment configured for a given toolchain
+    which          Display which binary will be run for a given command
+    doc            Open the documentation for the current toolchain
+...
+    self           Modify the rustup installation
+    set            Alter rustup settings
+    completions    Generate tab-completion scripts for your shell
+    help           Print this message or the help of the given subcommand(s)
+
+DISCUSSION:
+    Rustup installs The Rust Programming Language from the official
+    release channels, enabling you to easily switch between stable,
+    beta, and nightly compilers and keep them updated. It makes
+    cross-compiling simpler with binary builds of the standard library
+    for common platforms.
+
+    If you are new to Rust consider running `rustup doc --book` to
+    learn Rust.
+"""
+stderr = """
+error: To override the toolchain using the 'rustup +toolchain' syntax, make sure to prefix the toolchain override with a '+'
+
+"""