Wednesday, July 24, 2019

Re: Building a GWT project in Eclipse 2019-03+ with Java 11.

When I configure Eclipse 2019-06 to use this modified GWT 2.8.2 SDK, i am able to more or less get it to build, eventually, but with a flood of obscure "Validating GWT Components" errors that have to be tediously clicked through:

An internal error occurred during: "Validating GWT components".

class org.eclipse.jdt.internal.compiler.lookup.ProblemReferenceBinding cannot be cast to class org.eclipse.jdt.internal.compiler.lookup.PackageBinding (org.eclipse.jdt.internal.compiler.lookup.ProblemReferenceBinding and org.eclipse.jdt.internal.compiler.lookup.PackageBinding are in unnamed module of loader org.eclipse.osgi.internal.loader.EquinoxClassLoader @57cd77e1)

So...first question: Did I miss an important step when I stripped those classes out of gwt-dev.jar? Or is there a way to make "Validating GWT components" stop complaining?

I don't think so. IMHO it looks like an Eclipse bug or the GWT plugin needs to be updated.

If we plan to announce that GWT 2.9 will be Java 11 compatible (syntax) then contributors will probably also sit down and make sure it works in IDEs either out of the box or by providing instructions how to configure Eclipse to make it work. In general all those 3rd party classes are included in gwt-dev.jar to just have a single dependency that needs to be added by the GWT plugin. The Maven release of GWT pulls those in as transitive dependencies. 

I think going forward GWT SDK release (non Maven release) should repackage all those dependencies into as it already does for some dependencies. That way we can also make sure that no dependency version conflicts exist on class path.

-- J.

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