Wednesday, July 5, 2017

Type Corruption migrating from GWT 2.6.1 => 2.7.0

We're seeing an issue in GWT 2.7.0 where if a Java Object is passed to a JS method that's wrapped with $entry(), then the type information is stripped off. 

So for example, if a LinkedMap instance is created, and passed through an API wrapped with $entry(), it's typeMarker$ attribute will be changed from a known function to a copy of that function, so that hasTypeMarker() returns false, and thus isJavaScriptObject() returns true - but ti's not a JavaScriptObject, it's a LinkedMap!

function isJavaScriptObject_0_g$(src_0_g$){
  return !isJavaString_0_g$(src_0_g$) && !hasTypeMarker_0_g$(src_0_g$);

function hasTypeMarker_0_g$(o_0_g$){
  return o_0_g$.typeMarker$ === typeMarkerFn_0_g$;

This worked as expected in GWT 2.6.1, but obviously not in GWT 2.7.0.  In the release notes for GWT 2.8.0 (RC1) here, I see this item:

"Fix instanceof for primitives & string."

but I'm not exactly sure what that is - it sounds like it may be related.  I took a look at closed issues on Github for GWT, but I wasn't able to isolate any issue corresponding to that, or matching the problem I described.

Anyone know what might be causing the issue above?

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