add support for Struct in Map

issue66_test.go

@@ -21,7 +21,7 @@ func TestPrivateSlice(t *testing.T) {
 		t.Fatalf("Error during the merge: %v", err)
 	}
 	if len(p1.PublicStrings) != 3 {
-		t.Error("5 elements should be in 'PublicStrings' field")
+		t.Error("3 elements should be in 'PublicStrings' field, when no append")
 	}
 	if len(p1.privateStrings) != 2 {
 		t.Error("2 elements should be in 'privateStrings' field")

issue90_test.go

@@ -0,0 +1,50 @@
+package mergo
+
+import (
+	"reflect"
+	"testing"
+)
+
+type CustomStruct struct {
+	SomeMap map[string]string
+}
+
+func TestMergoStructMap(t *testing.T) {
+	var testData = []struct {
+		name string
+		src  map[string]CustomStruct
+		dst  map[string]CustomStruct
+		exp  map[string]CustomStruct
+	}{
+		{name: "Normal",
+			dst: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "loosethis", "key2": "keepthis"}}},
+			src: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}},
+			exp: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10", "key2": "keepthis"}}},
+		},
+		{name: "Init of struct key", dst: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{}}},
+			src: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}},
+			exp: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}},
+		},
+		{name: "Not Init of struct key", dst: map[string]CustomStruct{},
+			src: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}},
+			exp: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}},
+		},
+		{name: "Nil struct key", dst: map[string]CustomStruct{"a": CustomStruct{SomeMap: nil}},
+			src: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}},
+			exp: map[string]CustomStruct{"a": CustomStruct{SomeMap: map[string]string{"key1": "key10"}}}},
+	}
+
+	for _, data := range testData {
+		dst := data.dst
+		src := data.src
+		exp := data.exp
+
+		err := Merge(&dst, src, WithAppendSlice, WithOverride)
+		if err != nil {
+			t.Errorf("mergo error was not nil, %v", err)
+		}
+		if !reflect.DeepEqual(dst, exp) {
+			t.Errorf("Actual: %#v did not match \nExpected: %#v", dst, exp)
+		}
+	}
+}

map.go

@@ -99,11 +99,11 @@ func deepMap(dst, src reflect.Value, visited map[uintptr]*visit, depth int, conf
 				continue
 			}
 			if srcKind == dstKind {
-				if err = deepMerge(dstElement, srcElement, visited, depth+1, config); err != nil {
+				if _, err = deepMerge(dstElement, srcElement, visited, depth+1, config); err != nil {
 					return
 				}
 			} else if dstKind == reflect.Interface && dstElement.Kind() == reflect.Interface {
-				if err = deepMerge(dstElement, srcElement, visited, depth+1, config); err != nil {
+				if _, err = deepMerge(dstElement, srcElement, visited, depth+1, config); err != nil {
 					return
 				}
 			} else if srcKind == reflect.Map {
@@ -157,7 +157,8 @@ func _map(dst, src interface{}, opts ...func(*Config)) error {
 	// To be friction-less, we redirect equal-type arguments
 	// to deepMerge. Only because arguments can be anything.
 	if vSrc.Kind() == vDst.Kind() {
-		return deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, config)
+		_, err := deepMerge(vDst, vSrc, make(map[uintptr]*visit), 0, config)
+		return err
 	}
 	switch vSrc.Kind() {
 	case reflect.Struct: