marshal: descend through all interfaces/pointers when looking for time.Time

Previously, we would ignore an interface{} containing a *time.Time and
treat it as a TextMarshaler.

Fixes #82

Author: DHowett

marshal.go

@@ -91,6 +91,13 @@ func (p *Encoder) marshalTime(val reflect.Value) cfValue {
 	return cfDate(time)
 }
 
+func innermostValue(val reflect.Value) reflect.Value {
+	for val.Kind() == reflect.Ptr || (val.Kind() == reflect.Interface && val.NumMethod() == 0) {
+		val = val.Elem()
+	}
+	return val
+}
+
 func (p *Encoder) marshal(val reflect.Value) cfValue {
 	if !val.IsValid() {
 		return nil
@@ -105,7 +112,7 @@ func (p *Encoder) marshal(val reflect.Value) cfValue {
 		return p.marshalTime(val)
 	}
 	if val.Kind() == reflect.Ptr || (val.Kind() == reflect.Interface && val.NumMethod() == 0) {
-		ival := val.Elem()
+		ival := innermostValue(val)
 		if ival.IsValid() && ival.Type() == timeType {
 			return p.marshalTime(ival)
 		}

marshal_test.go

@@ -103,3 +103,26 @@ func TestInterfaceFieldMarshal(t *testing.T) {
 		t.Log("expect non-zero data")
 	}
 }
+
+func TestMarshalInterfaceFieldPtrTime(t *testing.T) {
+	type X struct {
+		C interface{} // C's type is unknown
+	}
+
+	var sentinelTime = time.Date(2013, 11, 27, 0, 34, 0, 0, time.UTC)
+	x := &X{
+		C: &sentinelTime,
+	}
+
+	e := &Encoder{}
+	rval := reflect.ValueOf(x)
+	cf := e.marshal(rval)
+
+	if dict, ok := cf.(*cfDictionary); ok {
+		if _, ok := dict.values[0].(cfDate); !ok {
+			t.Error("inner value is not a cfDate")
+		}
+	} else {
+		t.Error("failed to marshal toplevel dictionary (?)")
+	}
+}