I get new javascript every GWT compile without changing java source

Question

GWT compiles the Java source into Javascript, and names the files according to a hash of their contents. I'm getting a new set of files every compile, because the javascript contents are changing, even when I don't change the source at all.

The files are different for OBF and PRETTY output, but if I set it to DETAILED, they're no longer different every compile. In PRETTY, I can see that all/most of the differences between compiles are in the value parameters for typeId. For example, a funciton called initValues() is called with different values for it's typeId parameter.

Answer 1

As far as I know, GWT will compile a new version every time you compile it, this is a feature ;)

You can use ant to control it though, so that it only builds the GWT section of your application if it's actually changed:

http://wiki.shiftyjelly.com/index.php/GWT#Use_The_Power_of_Ant_to_Build_Changes_Only

Answer 2

In PRETTY mode, the differences you see are allocation of Java Classes to TypeIds. It's how GWT manages run time type checking. You'll notice a table at the bottom of each script essentially mapping each typeId to all compatible superclasses. This is how GWT can still throw ClassCastException in JavaScript (though you should run into this very rarely!).

In OBF mode, the differences are due to the allocation of minified function names.

In both cases, it's due to the order the compiler is processing the code. Some internal symbol tables might be using a non-ordered collection store symbols for processing. It can happen for lots of reasons.