feat: ptr -> zero value and zero value -> ptr overrides now work

Author: Rocco Ciccone

copier.go

@@ -593,6 +593,9 @@ func set(to, from reflect.Value, deepCopy bool, converters map[converterPair]Typ
 			}
 			// allocate new `to` variable with default value (eg. *string -> new(string))
 			to.Set(reflect.New(to.Type().Elem()))
+		} else if from.Kind() != reflect.Ptr && from.IsZero() {
+			to.Set(reflect.Zero(to.Type()))
+			return true, nil
 		}
 		// depointer `to`
 		to = to.Elem()
@@ -607,6 +610,7 @@ func set(to, from reflect.Value, deepCopy bool, converters map[converterPair]Typ
 			}
 		}
 		if from.Kind() == reflect.Ptr && from.IsNil() {
+			to.Set(reflect.Zero(to.Type()))
 			return true, nil
 		}
 		if _, ok := to.Addr().Interface().(sql.Scanner); !ok && (toKind == reflect.Struct || toKind == reflect.Map || toKind == reflect.Slice) {

copier_tags_test.go

@@ -60,6 +60,29 @@ func TestCopyTagOverrideZeroValue(t *testing.T) {
 	}
 }
 
+func TestCopyTagOverridePtrToZeroValue(t *testing.T) {
+	options := copier.Option{IgnoreEmpty: true}
+	address := "21 Jump Street"
+	user1 := User1{ID: 100, Address: ""}
+	user2 := User2{DOB: "1 November, 1970", Address: &address, ID: 12345}
+
+	copier.CopyWithOption(&user2, user1, options)
+	if user2.Address != nil {
+		t.Error("Original Address was not overwritten")
+	}
+}
+
+func TestCopyTagOverrideZeroValueToPtr(t *testing.T) {
+	options := copier.Option{IgnoreEmpty: true}
+	user1 := User2{DOB: "1 November, 1970", Address: nil, ID: 12345}
+	user2 := User1{ID: 100, Address: "1 November, 1970"}
+
+	copier.CopyWithOption(&user2, user1, options)
+	if user1.Address != nil {
+		t.Error("Original Address was not overwritten")
+	}
+}
+
 func TestCopyTagOverridePtr(t *testing.T) {
 	options := copier.Option{IgnoreEmpty: true}
 	address := "21 Jump Street"