InferredOWLClassHierarchyProvider can crash depending on the reasoner implementation

[bdionne]

InferredOWLClassHierarchyProvider crashes if the reasoner returns an immutable collection. Using getEntitiesMinus seems to fix it.

[bdionne]

Thanks @matthewhorridge - is this one ok?

[andrewdbate]

Sorry to be commenting on a closed issue... but I'm currently getting this exact crash due to a reasoner returning an immutable collection.

The code immediately below the fix commited in 61c4f7b calls remove:

protege/protege-editor-owl/src/main/java/org/protege/editor/owl/model/hierarchy/cls/InferredOWLClassHierarchyProvider.java

Lines 94 to 100 in 6eb72cb

	// Class which is not Thing or Nothing
	subs.remove(owlNothing);
	for (Iterator<OWLClass> it = subs.iterator(); it.hasNext();) {
	if (!getReasoner().isSatisfiable(it.next())) {
	it.remove();
	}
	}

The problem seems to be that a valid implementation of getFlattened() is to return an immutable collection:

protege/protege-editor-owl/src/main/java/org/protege/editor/owl/model/hierarchy/cls/InferredOWLClassHierarchyProvider.java

Line 85 in 6eb72cb

Set<OWLClass> subs = getReasoner().getSubClasses(object, true).getFlattened();