Merge pull request #65 from nbrownus/nil-maps

Handle nil maps in dst

.travis.yml

@@ -4,4 +4,4 @@ install:
   - go get golang.org/x/tools/cmd/cover
   - go get github.com/mattn/goveralls
 script:
-  - $HOME/gopath/bin/goveralls -service=travis-ci -repotoken $COVERALLS_TOKEN
+  - $HOME/gopath/bin/goveralls -service=travis-ci

issue61_test.go

@@ -0,0 +1,22 @@
+package mergo
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestIssue61MergeNilMap(t *testing.T) {
+	type T struct {
+		I map[string][]string
+	}
+
+	t1 := T{}
+	t2 := T{I: map[string][]string{"hi": {"there"}}}
+	if err := Merge(&t1, t2); err != nil {
+		t.Fail()
+	}
+
+	if !reflect.DeepEqual(t2, T{I: map[string][]string{"hi": {"there"}}}) {
+		t.FailNow()
+	}
+}

merge.go

@@ -77,9 +77,8 @@ func deepMerge(dst, src reflect.Value, visited map[uintptr]*visit, depth int, co
 			}
 		}
 	case reflect.Map:
-		if len(src.MapKeys()) == 0 && !src.IsNil() && len(dst.MapKeys()) == 0 {
+		if dst.IsNil() && !src.IsNil() {
 			dst.Set(reflect.MakeMap(dst.Type()))
-			return
 		}
 		for _, key := range src.MapKeys() {
 			srcElement := src.MapIndex(key)