From 7985840da4ad23157a8726e6cf3b24a026f500e1 Mon Sep 17 00:00:00 2001
From: NicklasWallgren <nicklas.wallgren@stim.se>
Date: Tue, 10 Jan 2023 15:46:58 +0100
Subject: [PATCH] Fixed panic with nested pointer structs

---
 copier.go      | 12 +++++++++++-
 copier_test.go | 30 ++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/copier.go b/copier.go
index c699d70..0d21d14 100644
--- a/copier.go
+++ b/copier.go
@@ -270,7 +270,7 @@ func copier(toValue interface{}, fromValue interface{}, opt Option) (err error)
 				}
 
 				srcFieldName, destFieldName := getFieldName(name, flgs)
-				if fromField := source.FieldByName(srcFieldName); fromField.IsValid() && !shouldIgnore(fromField, opt.IgnoreEmpty) {
+				if fromField := fieldByNameOrZeroValue(source, srcFieldName); fromField.IsValid() && !shouldIgnore(fromField, opt.IgnoreEmpty) {
 					// process for nested anonymous field
 					destFieldNotSet := false
 					if f, ok := dest.Type().FieldByName(destFieldName); ok {
@@ -400,6 +400,16 @@ func copier(toValue interface{}, fromValue interface{}, opt Option) (err error)
 	return
 }
 
+func fieldByNameOrZeroValue(source reflect.Value, fieldName string) (value reflect.Value) {
+	defer func() {
+		if err := recover(); err != nil {
+			value = reflect.Value{}
+		}
+	}()
+
+	return source.FieldByName(fieldName)
+}
+
 func copyUnexportedStructFields(to, from reflect.Value) {
 	if from.Kind() != reflect.Struct || to.Kind() != reflect.Struct || !from.Type().AssignableTo(to.Type()) {
 		return
diff --git a/copier_test.go b/copier_test.go
index 08db7f3..de8dff8 100644
--- a/copier_test.go
+++ b/copier_test.go
@@ -1732,3 +1732,33 @@ func TestEmptySlice(t *testing.T) {
 		t.Error("from should be empty slice nil")
 	}
 }
+
+func TestNestedNilPointerStruct(t *testing.T) {
+	type destination struct {
+		Title string
+	}
+
+	type NestedSource struct {
+		ID int
+	}
+
+	type source struct {
+		Title string
+		*NestedSource
+	}
+
+	from := &source{
+		Title: "A title to be copied",
+	}
+
+	to := destination{}
+
+	err := copier.Copy(&to, from)
+	if err != nil {
+		t.Error("should not error")
+	}
+
+	if from.Title != to.Title {
+		t.Errorf("to (%v) value should equal from (%v) value", to.Title, from.Title)
+	}
+}