From a48d90c56126bdb54259406645e008099e942cdb Mon Sep 17 00:00:00 2001
From: Chu Ka-cheong <kc@enyksecurity.com>
Date: Tue, 20 Sep 2022 12:34:20 +0800
Subject: [PATCH] Fix unintented initialization of pointer fields

- Invalid sql.Null* values should be copied to pointer field as nil
- Embedded struct should be initialized if its member is copied directly
- Add test cases to cover the above cases
---
 copier.go      |  3 ++-
 copier_test.go | 60 ++++++++++++++++++++++++++++++++++++++++----------
 2 files changed, 50 insertions(+), 13 deletions(-)

diff --git a/copier.go b/copier.go
index 84efd25..e7b5410 100644
--- a/copier.go
+++ b/copier.go
@@ -263,7 +263,8 @@ func copier(toValue interface{}, fromValue interface{}, opt Option) (err error)
 					// process for nested anonymous field
 					destFieldNotSet := false
 					if f, ok := dest.Type().FieldByName(destFieldName); ok {
-						for idx := range f.Index {
+						// only initialize parent embedded struct pointer in the path
+						for idx := range f.Index[:len(f.Index)-1] {
 							destField := dest.FieldByIndex(f.Index[:idx+1])
 
 							if destField.Kind() != reflect.Ptr {
diff --git a/copier_test.go b/copier_test.go
index ec097cc..08db7f3 100644
--- a/copier_test.go
+++ b/copier_test.go
@@ -1089,6 +1089,36 @@ func TestAnonymousFields(t *testing.T) {
 		}
 	})
 
+	t.Run("Should work with exported ptr fields with same name src field", func(t *testing.T) {
+		type Nested struct {
+			A string
+		}
+		type parentA struct {
+			A string
+		}
+		type parentB struct {
+			*Nested
+		}
+
+		fieldValue := "a"
+		from := parentA{A: fieldValue}
+		to := parentB{}
+
+		err := copier.CopyWithOption(&to, &from, copier.Option{
+			DeepCopy: true,
+		})
+		if err != nil {
+			t.Errorf("Unexpected error: %v", err)
+			return
+		}
+
+		from.A = "b"
+
+		if to.Nested.A != fieldValue {
+			t.Errorf("should not change")
+		}
+	})
+
 	t.Run("Should work with exported fields", func(t *testing.T) {
 		type Nested struct {
 			A string
@@ -1356,19 +1386,21 @@ func TestScanner(t *testing.T) {
 func TestScanFromPtrToSqlNullable(t *testing.T) {
 	var (
 		from struct {
-			S    string
-			Sptr *string
-			T1   sql.NullTime
-			T2   sql.NullTime
-			T3   *time.Time
+			S     string
+			Sptr  *string
+			Snull sql.NullString
+			T1    sql.NullTime
+			T2    sql.NullTime
+			T3    *time.Time
 		}
 
 		to struct {
-			S    sql.NullString
-			Sptr sql.NullString
-			T1   time.Time
-			T2   *time.Time
-			T3   sql.NullTime
+			S     sql.NullString
+			Sptr  sql.NullString
+			Snull *string
+			T1    time.Time
+			T2    *time.Time
+			T3    sql.NullTime
 		}
 
 		s string
@@ -1393,8 +1425,12 @@ func TestScanFromPtrToSqlNullable(t *testing.T) {
 		t.Errorf("to.T1 should be Zero but %v", to.T1)
 	}
 
-	if to.T2 != nil && !to.T2.IsZero() {
-		t.Errorf("to.T2 should be Zero but %v", to.T2)
+	if to.T2 != nil {
+		t.Errorf("to.T2 should be nil but %v", to.T2)
+	}
+
+	if to.Snull != nil {
+		t.Errorf("to.Snull should be nil but %v", to.Snull)
 	}
 
 	now := time.Now()