test(json): add test case for #63

Author: dominicbarnes

json/json_test.go

@@ -1578,7 +1578,6 @@ func TestGithubIssue41(t *testing.T) {
 			"expected: ", expectedString,
 		)
 	}
-
 }
 
 func TestGithubIssue44(t *testing.T) {
@@ -1602,6 +1601,40 @@ func (r *rawJsonString) UnmarshalJSON(b []byte) error {
 	return nil
 }
 
+// See https://github.com/segmentio/encoding/issues/63
+// In short, embedding a struct pointer resulted in an incorrect memory address
+// as we were still looking to the parent struct to start and only using offsets
+// which resulted in the wrong values being extracted.
+func TestGithubIssue63(t *testing.T) {
+	expectedString := `{"my_field":"test","my_other_field":"testing","code":1}`
+
+	type MyStruct struct {
+		MyField      string `json:"my_field,omitempty"`
+		MyOtherField string `json:"my_other_field"`
+		MyEmptyField string `json:"my_empty_field,omitempty"`
+	}
+
+	type MyStruct2 struct {
+		*MyStruct
+		Code int `json:"code"`
+	}
+
+	input := MyStruct2{
+		MyStruct: &MyStruct{
+			MyField:      "test",
+			MyOtherField: "testing",
+		},
+		Code: 1,
+	}
+
+	if b, err := Marshal(input); err != nil {
+		t.Error(err)
+	} else if string(b) != expectedString {
+		t.Errorf("got:      %s", string(b))
+		t.Errorf("expected: %s", expectedString)
+	}
+}
+
 func TestSetTrustRawMessage(t *testing.T) {
 	buf := &bytes.Buffer{}
 	enc := NewEncoder(buf)