Error compiling class that implements trait (binary reference from grails-testing-support)

[AntonPanikov]

I am using Grails framework (3.3.x and 3.2.x) and all grails applications is always producing some strange compile error, while application is always compile fine with gradle and internal eclipse compiler. So I can run an app as regular spring boot app and debug it. The issue is if I have some gradle sub-project then any project that depends on it will be not compiled at all by internal eclipse compiler, so will be not runnable and I can not debug it, while gradle still can compile and run it.

I am using:
Eclipse Oxygen.3a Release (4.7.3a)
Groovy-Eclipse 3.1.0.xx-201808241936-e47

You can easily create sample app with sdkman or use attached one below:

1. Install sdkman:
   curl -s "https://get.sdkman.io" | bash
2. Source or open new shell:
   source "$HOME/.sdkman/bin/sdkman-init.sh"
3. Install grails:
   sdk i grails
4. Create sample app in some folder (grails-example):
   grails create-app --profile web --inplace

Import it into eclipse and add gradle nature, you will get:

The project was not built since its build path is incomplete. Cannot find the class file for grails.testing.services.ServiceUnitTest$Trait$FieldHelper$1. Fix the build path then try building this project

Based on source you can get different variations of this error referencing different classes from grail, like:

The project was not built since its build path is incomplete. Cannot find the class file for grails.artefact.Controller$Trait$FieldHelper$1. Fix the build path then try building this project

While project is actually compile fine and running.
grails-sample.zip

[eric-milles]

There are two facets to this issue:

1. Groovy-Eclipse is performing very eager resolution of member types when trying to resolve names in a compilation unit.
2. Grails is not including the trait member types in some of their distributions. For example, grails.testing.services.ServiceUnitTest is a trait, but only the outer class ServiceUnitTest is included in the grails-testing-support artifact. The class files list member types such as ServiceUnitTest$Trait$FieldHelper$1, so it is only logical that an IDE might try to resolve them at some point.

[eric-milles]

Here is the source of the error during compilation:

		// walk all visible interfaces to find ambiguous references
		if (interfacesToVisit != null) {
			ProblemReferenceBinding ambiguous = null;
			done : for (int i = 0; i < nextPosition; i++) {
				ReferenceBinding anInterface = interfacesToVisit[i];
				unitScope.recordReference(anInterface, typeName);
				if ((memberType = anInterface.getMemberType(typeName)) != null) {

The interface being examined is ServiceUnitTest and the typeName string is "java".

[eric-milles]

Even if inner class resolve can be deferred, compilation against a trait requires resolution of its inner class "helper" types:

        addPhaseOperation(new PrimaryClassNodeOperation() {
            public void call(SourceUnit source, GeneratorContext context,
                             ClassNode classNode) throws CompilationFailedException {
                TraitComposer.doExtendTraits(classNode, source, CompilationUnit.this);
            }
        }, Phases.CANONICALIZATION);
// From TraitComposer:
    public static void doExtendTraits(final ClassNode cNode, final SourceUnit unit, final CompilationUnit cu) {
        if (cNode.isInterface()) return;
        boolean isItselfTrait = Traits.isTrait(cNode);
        SuperCallTraitTransformer superCallTransformer = new SuperCallTraitTransformer(unit);
        if (isItselfTrait) {
            checkTraitAllowed(cNode, unit);
            return;
        }
        if (!cNode.getNameWithoutPackage().endsWith(Traits.TRAIT_HELPER)) {
            List<ClassNode> traits = findTraits(cNode);
            for (ClassNode trait : traits) {
                TraitHelpersTuple helpers = Traits.findHelpers(trait); // this line tries to resolve trait helpers
                applyTrait(trait, cNode, helpers);
                superCallTransformer.visitClass(cNode);
                if (unit!=null) {
                    ASTTransformationCollectorCodeVisitor collector = new ASTTransformationCollectorCodeVisitor(unit, cu.getTransformLoader());
                    collector.visitClass(cNode);
                }
            }
        }
    }

[eric-milles]

Seems like this was reported to the Grails project as well: grails/grails-testing-support#31

[eric-milles]

Ready to test

[AntonPanikov]

It is working right now, this type of compilation is gone, but I am getting:

The method cannot be declared static; static methods can only be declared in a static or top level type

for something like this:

class Test {

    class TestInner {
        static {
        }

    }
}

I am on 3.1.0.xx-201809141915-e47

[eric-milles]

Can you file a separate issue? The original issue has been fixed.