JS: ensure that extension values are serialized even if they're falsy

There was a bug where for JavaScript we would only serialize an
extension value if it evaluated as truthy, which meant that values like
0 would get silently dropped (even in proto2, where field presence is
significant). This fixes issue #2605, and takes care of the output of
toObject() in addition to the binary format.

1 files changed, 2 insertions, 2 deletions

diff --git a/js/message.js b/js/message.js
index 05d34e9d..4e2517d3 100644
--- a/js/message.js
+++ b/js/message.js
@@ -497,7 +497,7 @@ jspb.Message.toObjectExtension = function(proto, obj, extensions,
   for (var fieldNumber in extensions) {
     var fieldInfo = extensions[fieldNumber];
     var value = getExtensionFn.call(proto, fieldInfo);
-    if (value) {
+    if (goog.isDefAndNotNull(value)) {
       for (var name in fieldInfo.fieldName) {
         if (fieldInfo.fieldName.hasOwnProperty(name)) {
           break; // the compiled field name
@@ -541,7 +541,7 @@ jspb.Message.serializeBinaryExtensions = function(proto, writer, extensions,
                       'without binary serialization support');
     }
     var value = getExtensionFn.call(proto, fieldInfo);
-    if (value) {
+    if (goog.isDefAndNotNull(value)) {
       if (fieldInfo.isMessageType()) {
         // If the message type of the extension was generated without binary
         // support, there may not be a binary message serializer function, and