yamldiff updates with better array diff

cmd/yamldiff/yamldiff.go

@@ -46,12 +46,17 @@ func Type(elem any) TypeId {
 	}
 }
 
-func subtract(yaml1 yaml.MapSlice, yaml2 yaml.MapSlice) yaml.MapSlice {
+// hack to be able to compare slices and dictionires that cannot be put into a map.
+func strval(v any) string {
+	return fmt.Sprintf("%v", v)
+}
+
+func subtract(yaml2 yaml.MapSlice, yaml1 yaml.MapSlice) yaml.MapSlice {
 	res := make(yaml.MapSlice, 0)
 	for _, item := range yaml2 {
 		k := item.Key
-		v1 := item.Value
-		v2 := yaml1.ToMap()[k]
+		v2 := item.Value
+		v1 := yaml1.ToMap()[k]
 		switch {
 		case reflect.DeepEqual(v1, v2):
 			// delete is implicit by not copying to the output
@@ -61,9 +66,29 @@ func subtract(yaml1 yaml.MapSlice, yaml2 yaml.MapSlice) yaml.MapSlice {
 				res = append(res, item)
 			}
 		case Type(v1) == Slice && Type(v2) == Slice:
-			if !reflect.DeepEqual(v1, v2) {
-				res = append(res, item)
+			v2set := make(map[string]bool)
+			v1set := make(map[string]bool)
+			stringToValue := make(map[any]any)
+			for _, v := range v2.([]any) {
+				sval := strval(v)
+				stringToValue[sval] = v
+				v2set[sval] = true
 			}
+			for _, v := range v1.([]any) {
+				v1set[strval(v)] = true
+			}
+			s := make([]any, 0)
+			for k2, _ := range v2set {
+				if v1set[k2] {
+					s = append(s, "<UNMODIFIED>")
+				} else {
+					s = append(s, stringToValue[k2])
+				}
+			}
+			res = append(res, yaml.MapItem{
+				Key:   k,
+				Value: s,
+			})
 		default:
 			res = append(res, item)
 		}
@@ -77,6 +102,7 @@ func main() {
 Usage: yamldiff <file1> <file2>")
   Shows changes and additions made in <file2> w.r.t. <file1> 
 `)
+		os.Exit(1)
 	}
 	file1 := os.Args[1]
 	file2 := os.Args[2]
@@ -84,7 +110,7 @@ Usage: yamldiff <file1> <file2>")
 	yaml1 := parse(read(file1))
 	yaml2 := parse(read(file2))
 
-	subtract(yaml2, yaml1)
+	yaml2 = subtract(yaml2, yaml1)
 
 	enc := yaml.NewEncoder(os.Stdout,
 		yaml.UseLiteralStyleIfMultiline(true),