helper/schema: FieldReaderMap should mark map as exists if anything set

helper/schema/field_reader_map.go

@@ -56,10 +56,11 @@ func (r *MapFieldReader) readMap(k string) (FieldReadResult, error) {
 	prefix := k + "."
 	r.Map.Range(func(k, v string) bool {
 		if strings.HasPrefix(k, prefix) {
+			resultSet = true
+
 			key := k[len(prefix):]
 			if key != "#" {
 				result[key] = v
-				resultSet = true
 			}
 		}
 

helper/schema/field_reader_map_test.go

@@ -49,11 +49,14 @@ func TestMapFieldReader(t *testing.T) {
 func TestMapFieldReader_extra(t *testing.T) {
 	r := &MapFieldReader{
 		Schema: map[string]*Schema{
-			"mapDel": &Schema{Type: TypeMap},
+			"mapDel":   &Schema{Type: TypeMap},
+			"mapEmpty": &Schema{Type: TypeMap},
 		},
 
 		Map: BasicMapReader(map[string]string{
 			"mapDel": "",
+
+			"mapEmpty.#": "0",
 		}),
 	}
 
@@ -71,6 +74,14 @@ func TestMapFieldReader_extra(t *testing.T) {
 			false,
 			false,
 		},
+
+		"mapEmpty": {
+			[]string{"mapEmpty"},
+			map[string]interface{}{},
+			true,
+			false,
+			false,
+		},
 	}
 
 	for name, tc := range cases {