fix default for targetPath if not specified

Author: SteveL-MSFT

dsc/tests/dsc_functions.tests.ps1

@@ -42,4 +42,24 @@ Describe 'tests for function expressions' {
         $out = $config_yaml | dsc config --target-path $PSHOME get | ConvertFrom-Json
         $out.results[0].result.actualState.output | Should -BeExactly $expected
     }
+
+    It 'default targetPath() is correct for the OS' {
+        $config_yaml = @'
+            $schema: https://raw.githubusercontent.com/PowerShell/DSC/main/schemas/2024/04/config/document.json
+            resources:
+            - name: Echo
+              type: Microsoft.DSC.Debug/Echo
+              properties:
+                output: "[targetPath()]"
+'@
+
+        $expected = if ($IsWindows) {
+            $env:SYSTEMDRIVE + '\'
+        } else {
+            '/'
+        }
+        $out = $config_yaml | dsc config get | ConvertFrom-Json
+        $LASTEXITCODE | Should -Be 0
+        $out.results[0].result.actualState.output | Should -BeExactly $expected
+    }
 }

dsc_lib/src/configure/context.rs

@@ -25,7 +25,7 @@ impl Context {
         Self {
             execution_type: ExecutionKind::Actual,
             outputs: HashMap::new(),
-            target_path: PathBuf::new(),
+            target_path: get_default_os_target_path(),
             parameters: HashMap::new(),
             security_context: match get_security_context() {
                 SecurityContext::Admin => SecurityContextKind::Elevated,
@@ -42,3 +42,15 @@ impl Default for Context {
         Self::new()
     }
 }
+
+#[cfg(target_os = "windows")]
+fn get_default_os_target_path() -> PathBuf {
+    // use SYSTEMDRIVE env var to get the default target path
+    let system_drive = std::env::var("SYSTEMDRIVE").unwrap_or_else(|_| "C:".to_string());
+    PathBuf::from(system_drive).join("\\")
+}
+
+#[cfg(not(target_os = "windows"))]
+fn get_default_os_target_path() -> PathBuf {
+    PathBuf::from("/")
+}