Shaving off some unneeded calls, saving CPU cycles

I know it’s very unlikely that a user will notice the difference, but
why range through the list, generate the set and calculate the
hashcode, only to find out that indexMap == nil (e.g. don’t do anything
with the generated hashcode).

As indexMap is only needed when len(parts) > 0, why not only create and
fill it (in one go) when len(parts) > 0?

helper/schema/resource_data.go

@@ -339,12 +339,10 @@ func (d *ResourceData) getSet(
 	var indexMap map[int]int
 	if len(parts) > 0 {
 		indexMap = make(map[int]int)
-	}
 
-	// Build the set from all the items using the given hash code
-	for i, v := range list {
-		code := s.add(v)
-		if indexMap != nil {
+		// Build the set from all the items using the given hash code
+		for i, v := range list {
+			code := s.add(v)
 			indexMap[code] = i
 		}
 	}