Improve Windows update parity

install.ps1

@@ -24,6 +24,24 @@ function Require-Command($Name) {
     }
 }
 
+function Ensure-Cargo {
+    if (Get-Command cargo -ErrorAction SilentlyContinue) {
+        return
+    }
+    if (-not (Get-Command winget -ErrorAction SilentlyContinue)) {
+        throw "cargo not found and winget is unavailable; install Rust from https://rustup.rs or set DOSH_USE_PREBUILT=1"
+    }
+    Write-Host "cargo not found; installing Rust toolchain with winget/rustup"
+    winget install --id Rustlang.Rustup -e --accept-package-agreements --accept-source-agreements
+    $cargoBin = Join-Path $HOME ".cargo\bin"
+    if (Test-Path $cargoBin) {
+        $env:Path = "$cargoBin;$env:Path"
+    }
+    if (-not (Get-Command cargo -ErrorAction SilentlyContinue)) {
+        throw "cargo was installed but is not available in this terminal yet; open a new terminal and rerun dosh update"
+    }
+}
+
 function Normalize-Arch {
     $arch = if ($env:PROCESSOR_ARCHITEW6432) { $env:PROCESSOR_ARCHITEW6432 } else { $env:PROCESSOR_ARCHITECTURE }
     switch ($arch) {
@@ -367,7 +385,7 @@ function Install-Prebuilt {
 }
 
 function Install-FromSource {
-    Require-Command cargo
+    Ensure-Cargo
     if (Test-Path "Cargo.toml") {
         $src = (Get-Location).Path
     } else {

src/bin/dosh-client.rs

@@ -4428,7 +4428,7 @@ fn run_update(config: &dosh::config::ClientConfig, options: UpdateOptions) -> Re
         env!("CARGO_PKG_VERSION"),
         latest_release_tag(&repo)?.as_deref(),
     );
-    let status = run_update_installer(
+    run_update_installer(
         config,
         &repo,
         &installer,
@@ -4437,9 +4437,6 @@ fn run_update(config: &dosh::config::ClientConfig, options: UpdateOptions) -> Re
         &use_prebuilt,
         binary_version.as_deref(),
     )?;
-    if !status.success() {
-        return Err(anyhow!("dosh update failed with status {status}"));
-    }
     Ok(())
 }
 
@@ -4451,7 +4448,7 @@ fn run_update_installer(
     update_cache: &str,
     use_prebuilt: &str,
     binary_version: Option<&str>,
-) -> Result<std::process::ExitStatus> {
+) -> Result<()> {
     if cfg!(windows) {
         let script = windows_update_script(
             config,
@@ -4462,15 +4459,18 @@ fn run_update_installer(
             use_prebuilt,
             binary_version,
         );
-        return Command::new("powershell.exe")
+        let script = windows_deferred_update_script(std::process::id(), &script);
+        Command::new("powershell.exe")
             .arg("-NoProfile")
             .arg("-ExecutionPolicy")
             .arg("Bypass")
             .arg("-Command")
             .arg(script)
             .stdin(Stdio::null())
-            .status()
-            .context("run dosh update installer");
+            .spawn()
+            .context("start deferred dosh update installer")?;
+        println!("dosh update started; the installer will run after this process exits");
+        return Ok(());
     }
     let script = unix_update_script(
         config,
@@ -4481,12 +4481,16 @@ fn run_update_installer(
         use_prebuilt,
         binary_version,
     );
-    Command::new("sh")
+    let status = Command::new("sh")
         .arg("-c")
         .arg(script)
         .stdin(Stdio::null())
         .status()
-        .context("run dosh update installer")
+        .context("run dosh update installer")?;
+    if !status.success() {
+        return Err(anyhow!("dosh update failed with status {status}"));
+    }
+    Ok(())
 }
 
 fn unix_update_script(
@@ -4566,6 +4570,17 @@ fn windows_update_script(
     script
 }
 
+fn windows_deferred_update_script(parent_pid: u32, installer_script: &str) -> String {
+    format!(
+        "$ErrorActionPreference='Stop';\
+         $ProgressPreference='SilentlyContinue';\
+         while (Get-Process -Id {parent_pid} -ErrorAction SilentlyContinue) {{ \
+             Start-Sleep -Milliseconds 100 \
+         }};\
+         {installer_script}"
+    )
+}
+
 fn powershell_string(value: &str) -> String {
     format!("'{}'", value.replace('\'', "''"))
 }
@@ -10175,7 +10190,8 @@ mod tests {
         trace_report_warnings, unix_update_script, update_binary_version_for_installer,
         update_installer_url, update_version_status, upsert_managed_block, valid_forward_host,
         vscode_safe_alias, wake_repaint_retry_deadline, windows_command_word,
-        windows_mode_from_readonly, windows_readonly_from_mode, windows_update_script,
+        windows_deferred_update_script, windows_mode_from_readonly, windows_readonly_from_mode,
+        windows_update_script,
     };
     use dosh::config::{ClientConfig, CommandExtension, HostConfig};
     use dosh::native::EnvVar;
@@ -12423,6 +12439,31 @@ mod tests {
         assert!(!windows.contains(" sh -s "));
     }
 
+    #[test]
+    fn windows_update_script_waits_for_parent_before_replacing_locked_exe() {
+        let installer = windows_update_script(
+            &ClientConfig::default(),
+            "https://git.palav.dev/Palav/dosh.git",
+            "https://git.palav.dev/Palav/dosh/raw/branch/main/install.ps1",
+            "client",
+            "C:\\Users\\palav\\AppData\\Local\\dosh\\source",
+            "1",
+            None,
+        );
+        let deferred = windows_deferred_update_script(4242, &installer);
+        assert!(deferred.contains("Get-Process -Id 4242 -ErrorAction SilentlyContinue"));
+        assert!(deferred.contains("Start-Sleep -Milliseconds 100"));
+        assert!(
+            deferred.contains(
+                "irm 'https://git.palav.dev/Palav/dosh/raw/branch/main/install.ps1' | iex"
+            )
+        );
+        assert!(
+            deferred.find("Get-Process -Id 4242").unwrap()
+                < deferred.find("irm 'https://git.palav.dev").unwrap()
+        );
+    }
+
     #[test]
     fn update_uses_local_tag_when_release_latest_is_older() {
         assert_eq!(

tests/release_scripts.rs

@@ -145,6 +145,20 @@ fn windows_installer_reuses_persistent_source_update_cache() {
     );
 }
 
+#[test]
+fn windows_installer_bootstraps_rust_for_source_fallback_like_unix() {
+    let install = include_str!("../install.sh");
+    let ps1 = include_str!("../install.ps1");
+    assert!(install.contains("ensure_cargo()"));
+    assert!(install.contains("cargo not found; installing Rust toolchain with rustup"));
+    assert!(ps1.contains("function Ensure-Cargo"));
+    assert!(ps1.contains("cargo not found; installing Rust toolchain with winget/rustup"));
+    assert!(ps1.contains("winget install --id Rustlang.Rustup"));
+    assert!(ps1.contains("--accept-package-agreements --accept-source-agreements"));
+    assert!(ps1.contains("Ensure-Cargo"));
+    assert!(!ps1.contains("Require-Command cargo"));
+}
+
 #[test]
 fn windows_installer_adds_user_path_idempotently() {
     let ps1 = include_str!("../install.ps1");