encoding/json: disable anonymous fields

We should, after Go 1, make them work the same as
package xml, that is, make them appear in the outer
struct.  For now turn them off so that people do not
depend on the old behavior.

Fixing them is issue 3069.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5656102

1 files changed, 29 insertions, 0 deletions

diff --git a/src/pkg/encoding/json/decode_test.go b/src/pkg/encoding/json/decode_test.go
index 775becfa7c..0eec586a9b 100644
--- a/src/pkg/encoding/json/decode_test.go
+++ b/src/pkg/encoding/json/decode_test.go
@@ -619,3 +619,32 @@ func TestRefUnmarshal(t *testing.T) {
 		t.Errorf("got %+v, want %+v", got, want)
 	}
 }
+
+// Test that anonymous fields are ignored.
+// We may assign meaning to them later.
+func TestAnonymous(t *testing.T) {
+	type S struct {
+		T
+		N int
+	}
+
+	data, err := Marshal(new(S))
+	if err != nil {
+		t.Fatalf("Marshal: %v", err)
+	}
+	want := `{"N":0}`
+	if string(data) != want {
+		t.Fatalf("Marshal = %#q, want %#q", string(data), want)
+	}
+
+	var s S
+	if err := Unmarshal([]byte(`{"T": 1, "T": {"Y": 1}, "N": 2}`), &s); err != nil {
+		t.Fatalf("Unmarshal: %v", err)
+	}
+	if s.N != 2 {
+		t.Fatal("Unmarshal: did not set N")
+	}
+	if s.T.Y != 0 {
+		t.Fatal("Unmarshal: did set T.Y")
+	}
+}