Visual Studio: Let the user choose install method

Also give advice on which option users should choose.

Author: ChrisDenton

src/cli/self_update.rs

@@ -313,7 +313,7 @@ static MSVC_AUTO_INSTALL_MESSAGE: &str = r#"# Rust Visual C++ prerequisites
 
 Rust requires a linker and Windows API libraries but they don't seem to be available.
 
-These components can be acquired by installing Visual Studio.
+These components can be acquired through a Visual Studio installer.
 
 "#;
 
@@ -376,37 +376,38 @@ pub(crate) fn install(
             warn!("installing msvc toolchain without its prerequisites");
         } else if !quiet && plan == VsInstallPlan::Automatic {
             md(&mut term, MSVC_AUTO_INSTALL_MESSAGE);
-            if common::confirm(
-                "\nAutomatically download and install Visual Studio 2022 Community edition? (Y/n)",
-                true,
-            )? {
-                match try_install_msvc(&opts) {
-                    Err(e) => {
-                        // Make sure the console doesn't exit before the user can
-                        // see the error and give the option to continue anyway.
-                        report_error(&e);
-                        if !common::confirm("\nContinue installing rustup? (y/N)", false)? {
-                            info!("aborting installation");
+            match windows::choose_vs_install()? {
+                Some(VsInstallPlan::Automatic) => {
+                    match try_install_msvc(&opts) {
+                        Err(e) => {
+                            // Make sure the console doesn't exit before the user can
+                            // see the error and give the option to continue anyway.
+                            report_error(&e);
+                            if !common::question_bool("\nContinue?", false)? {
+                                info!("aborting installation");
+                                return Ok(utils::ExitCode(0));
+                            }
+                        }
+                        Ok(ContinueInstall::No) => {
+                            ensure_prompt()?;
                             return Ok(utils::ExitCode(0));
                         }
+                        _ => {}
                     }
-                    Ok(ContinueInstall::No) => {
-                        ensure_prompt()?;
+                }
+                Some(VsInstallPlan::Manual) => {
+                    md(&mut term, MSVC_MANUAL_INSTALL_MESSAGE);
+                    if !common::question_bool("\nContinue?", false)? {
+                        info!("aborting installation");
                         return Ok(utils::ExitCode(0));
                     }
-                    _ => {}
-                }
-            } else {
-                md(&mut term, MSVC_MANUAL_INSTALL_MESSAGE);
-                if !common::confirm("\nContinue? (y/N)", false)? {
-                    info!("aborting installation");
-                    return Ok(utils::ExitCode(0));
                 }
+                None => {}
             }
         } else {
             md(&mut term, MSVC_MESSAGE);
             md(&mut term, MSVC_MANUAL_INSTALL_MESSAGE);
-            if !common::confirm("\nContinue? (y/N)", false)? {
+            if !common::question_bool("\nContinue?", false)? {
                 info!("aborting installation");
                 return Ok(utils::ExitCode(0));
             }

src/cli/self_update/windows.rs

@@ -2,6 +2,7 @@ use std::cell::RefCell;
 use std::env::{consts::EXE_SUFFIX, split_paths};
 use std::ffi::{OsStr, OsString};
 use std::fmt;
+use std::io::Write;
 use std::os::windows::ffi::{OsStrExt, OsStringExt};
 use std::path::Path;
 use std::process::Command;
@@ -27,6 +28,58 @@ pub(crate) fn ensure_prompt() -> Result<()> {
     Ok(())
 }
 
+fn choice(max: u8) -> Result<Option<u8>> {
+    write!(process().stdout(), ">")?;
+
+    let _ = std::io::stdout().flush();
+    let input = common::read_line()?;
+
+    let r = match str::parse(&input) {
+        Ok(n) if n <= max => Some(n),
+        _ => None,
+    };
+
+    writeln!(process().stdout())?;
+    Ok(r)
+}
+
+pub(crate) fn choose_vs_install() -> Result<Option<VsInstallPlan>> {
+    writeln!(
+        process().stdout(),
+        "\n1) Quick install via the Visual Studio Community installer"
+    )?;
+    writeln!(
+        process().stdout(),
+        "   (free for individuals, academic uses, and open source)."
+    )?;
+    writeln!(
+        process().stdout(),
+        "\n2) Manually install the prerequisites"
+    )?;
+    writeln!(
+        process().stdout(),
+        "   (for enterprise and advanced users)."
+    )?;
+    writeln!(process().stdout(), "\n3) Don't install the prerequisites")?;
+    writeln!(
+        process().stdout(),
+        "   (if you're targetting the GNU ABI).\n"
+    )?;
+
+    let choice = loop {
+        if let Some(n) = choice(3)? {
+            break n;
+        }
+        writeln!(process().stdout(), "Select option 1, 2 or 3")?;
+    };
+    let plan = match choice {
+        1 => Some(VsInstallPlan::Automatic),
+        2 => Some(VsInstallPlan::Manual),
+        _ => None,
+    };
+    Ok(plan)
+}
+
 #[derive(PartialEq, Eq)]
 pub(crate) enum VsInstallPlan {
     Automatic,