fix(cp): ensure parent dirs for symlinks, check end marker unmarshal, remove unused OnError callback

- Add os.MkdirAll before creating symlinks in CpFromInstance to prevent ENOENT
- Check json.Unmarshal error for end marker to avoid indefinite hangs on malformed messages
- Remove unused OnError callback from CpCallbacks (never invoked)

Author: rgarcia

lib/cp.go

@@ -52,10 +52,9 @@ func ExtractCpConfig(opts []requestconfig.RequestOption) (CpConfig, error) {
 
 // CpCallbacks provides optional progress callbacks for copy operations.
 type CpCallbacks struct {
-	OnFileStart func(path string, size int64)    // Called when a file starts copying
-	OnProgress  func(bytesCopied int64)          // Called as bytes are copied
-	OnFileEnd   func(path string)                // Called when a file finishes copying
-	OnError     func(path string, err error)     // Called on per-file errors (non-fatal)
+	OnFileStart func(path string, size int64) // Called when a file starts copying
+	OnProgress  func(bytesCopied int64)       // Called as bytes are copied
+	OnFileEnd   func(path string)             // Called when a file finishes copying
 }
 
 // CpToInstanceOptions configures a copy-to-instance operation
@@ -471,15 +470,19 @@ func CpFromInstance(ctx context.Context, cfg CpConfig, opts CpFromInstanceOption
 					if opts.Archive && (header.Uid != 0 || header.Gid != 0) {
 						os.Chown(targetPath, int(header.Uid), int(header.Gid))
 					}
-				} else if header.IsSymlink {
-					// Validate symlink target to prevent pointing outside destination
-					if filepath.IsAbs(header.LinkTarget) || strings.HasPrefix(filepath.Clean(header.LinkTarget), "..") {
-						return fmt.Errorf("invalid symlink target: %s", header.LinkTarget)
-					}
-					os.Remove(targetPath)
-					if err := os.Symlink(header.LinkTarget, targetPath); err != nil {
-						return fmt.Errorf("create symlink %s: %w", targetPath, err)
-					}
+			} else if header.IsSymlink {
+				// Validate symlink target to prevent pointing outside destination
+				if filepath.IsAbs(header.LinkTarget) || strings.HasPrefix(filepath.Clean(header.LinkTarget), "..") {
+					return fmt.Errorf("invalid symlink target: %s", header.LinkTarget)
+				}
+				// Create parent directory if needed
+				if err := os.MkdirAll(filepath.Dir(targetPath), 0755); err != nil {
+					return fmt.Errorf("create parent dir for symlink: %w", err)
+				}
+				os.Remove(targetPath)
+				if err := os.Symlink(header.LinkTarget, targetPath); err != nil {
+					return fmt.Errorf("create symlink %s: %w", targetPath, err)
+				}
 					// Apply ownership if archive mode (use Lchown for symlinks)
 					if opts.Archive && (header.Uid != 0 || header.Gid != 0) {
 						os.Lchown(targetPath, int(header.Uid), int(header.Gid))
@@ -501,7 +504,9 @@ func CpFromInstance(ctx context.Context, cfg CpConfig, opts CpFromInstanceOption
 
 			case "end":
 				var endMarker cpEndMarker
-				json.Unmarshal(message, &endMarker)
+				if err := json.Unmarshal(message, &endMarker); err != nil {
+					return fmt.Errorf("invalid end marker: %w", err)
+				}
 
 				if currentFile != nil {
 					currentFile.Close()