fix: better handling of windows paths (#646)

Issue #, if available:

*Description of changes:*
- Handle edge cases when dealing with Windows paths

*Testing done:*
- Tested on my Windows host


- [x] I've reviewed the guidance in CONTRIBUTING.md


#### License Acceptance

By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache 2.0 license.

Signed-off-by: Justin Alvarez <[email protected]>

pkg/disk/disk_windows.go

@@ -33,12 +33,16 @@ func (m *userDataDiskManager) EnsureUserDataDisk() error {
 		if err := m.fs.MkdirAll(disksDir, 0o700); err != nil {
 			return fmt.Errorf("could not create persistent disk directory: %w", err)
 		}
+	} else if err != nil {
+		return fmt.Errorf("error stating disksDir %q: %w", disksDir, err)
 	}
 
 	if _, err := m.fs.Stat(diskPath); errors.Is(err, fs.ErrNotExist) {
 		if err := m.createDisk(diskPath); err != nil {
 			return fmt.Errorf("could not create persistent disk: %w", err)
 		}
+	} else if err != nil {
+		return fmt.Errorf("error stating disksDir %q: %w", diskPath, err)
 	}
 
 	if err := m.attachDisk(diskPath); err != nil {

pkg/path/finch.go

@@ -16,21 +16,6 @@ import (
 // Finch provides a set of methods that calculate paths relative to the Finch path.
 type Finch string
 
-// FinchRootDir returns the path to the Finch root directory.
-// $HOME on UNIX and $LocalAppData on Windows.
-func (Finch) FinchRootDir(ffd FinchFinderDeps) (string, error) {
-	if runtime.GOOS == "windows" {
-		return ffd.Env("LOCALAPPDATA"), nil
-	}
-
-	home, err := ffd.GetUserHome()
-	if err != nil {
-		return "", err
-	}
-
-	return home, nil
-}
-
 // FinchDir returns the path to the Finch config directory.
 func (Finch) FinchDir(rootDir string) string {
 	return filepath.Join(rootDir, ".finch")

pkg/path/finch_unix.go

@@ -0,0 +1,17 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build !windows
+// +build !windows
+
+package path
+
+// FinchRootDir returns the path to the Finch root directory, which is $HOME on UNIX.
+func (Finch) FinchRootDir(ffd FinchFinderDeps) (string, error) {
+	home, err := ffd.GetUserHome()
+	if err != nil {
+		return "", err
+	}
+
+	return home, nil
+}

pkg/path/finch_windows.go

@@ -0,0 +1,24 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build windows
+// +build windows
+
+package path
+
+import (
+	"golang.org/x/sys/windows/registry"
+)
+
+// FinchRootDir returns the path to the Finch root directory, which is %LOCALAPPDATA% on Windows.
+// It also canonicalizes any environment variables that may be unexpanded in the path so that all
+// paths based on it can be passed safely to other programs which may execute outside of the user's context.
+func (Finch) FinchRootDir(ffd FinchFinderDeps) (string, error) {
+	appDir := ffd.Env("LOCALAPPDATA")
+	expandedPath, err := registry.ExpandString(appDir)
+	if err != nil {
+		return "", err
+	}
+
+	return expandedPath, nil
+}