Merge pull request #3257 from fatih/fix-nil-setting-schema

schema: delete non existing values

helper/schema/field_writer_map.go

@@ -207,7 +207,8 @@ func (w *MapFieldWriter) setPrimitive(
 	k := strings.Join(addr, ".")
 
 	if v == nil {
-		delete(w.result, k)
+		// The empty string here means the value is removed.
+		w.result[k] = ""
 		return nil
 	}
 

helper/schema/field_writer_map_test.go

@@ -97,6 +97,15 @@ func TestMapFieldWriter(t *testing.T) {
 			},
 		},
 
+		"string nil": {
+			[]string{"string"},
+			nil,
+			false,
+			map[string]string{
+				"string": "",
+			},
+		},
+
 		"list of resources": {
 			[]string{"listResource"},
 			[]interface{}{