Merge resolvePath into windows-specific file; use (string, bool) API

Author: Copilot

go/extractor/util/BUILD.bazel

@@ -2,5 +2,5 @@
 
 package util
 
-// ResolveDrive is a no-op on non-Windows platforms.
-func ResolveDrive(driveRoot string) string { return "" }
+// ResolvePath is a no-op on non-Windows platforms.
+func ResolvePath(path string) string { return path }

go/extractor/util/subst.go

@@ -39,23 +39,48 @@ func init() {
 	available = true
 }
 
-// ResolveDrive resolves a subst'd drive root (e.g. "X:\") to its backing path.
-// Returns "" if the drive is not subst'd or on error.
-func ResolveDrive(driveRoot string) string {
+// ResolvePath resolves subst'd drive letters in a full path.
+// If the path starts with a subst'd drive letter, replaces it with the backing path.
+// Otherwise returns the path unchanged.
+func ResolvePath(path string) string {
+	if len(path) < 3 {
+		return path
+	}
+	if path[1] != ':' {
+		return path
+	}
+	if path[2] != '\\' && path[2] != '/' {
+		return path
+	}
+	c := path[0]
+	if !((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z')) {
+		return path
+	}
+
+	resolved, ok := resolveDrive(path[:3])
+	if !ok {
+		return path
+	}
+	return resolved + path[2:]
+}
+
+// resolveDrive resolves a subst'd drive root (e.g. "X:\") to its backing path.
+// The second return value is false if the drive is not subst'd or on error.
+func resolveDrive(driveRoot string) (string, bool) {
 	if !available {
-		return ""
+		return "", false
 	}
 	driveBytes, err := windows.ByteSliceFromString(driveRoot)
 	if err != nil {
-		return ""
+		return "", false
 	}
 	ret, _, _ := procResolve.Call(uintptr(unsafe.Pointer(&driveBytes[0])))
 	if ret == 0 {
-		return ""
+		return "", false
 	}
 	result := windows.BytePtrToString((*byte)(unsafe.Pointer(ret)))
 	if procFree != nil {
 		procFree.Call(ret)
 	}
-	return result
+	return result, true
 }