Description Henrik Lindberg 2011-01-17 17:49:33 EST

When the ConcreteSyntaxConstraintProvider checks a trailing optional group consisting of two data rules NPE is trown. The loop in ConcreteSyntaxConstraintProvider has no check if it produces a null element. (Checks for other types except group has a corresponding check). (But since I am not 100 sure if it has bad input, or if the error is local to ConcreteSyntaxConstraintProvider, I stopped investigating this further).

The rules that caused this was changed from something like:
ARule : x += X (COMMA OWS x += X)* endComma? ;
endComma : COMMA OWS ;

terminal COMMA : ',' ;
OWS : WHITE * ;
WHITE : (SP | TAB | CR | NL) ; 
// SP, TAB etc. are all terminal

When changed to:
ARule : x += X (COMMA OWS x += X)* (COMMA OWS)? ;

...a NPE is thrown because the logic below in createElement method does not check if it assigns
null to ele, which will be the case if no element in the group is considered "relevant".

// lines 341 - 357
} else if (ele instanceof Group || ele instanceof UnorderedGroup) {
	CompoundElement comp = (CompoundElement) ele;
	AbstractElement lastChild = null;
	for (AbstractElement o : comp.getElements())
		if (containsRelevantElement(o)) {
			if (lastChild == null)
				lastChild = o;
			else {
				List<AbstractElement> c = new ArrayList<AbstractElement>(comp.getElements());
				List<ISyntaxConstraint> e = createSummarizedAssignments(comp, c, semanticType, optional);
				if (e.size() == 1 && c.size() == 0)
					return e.get(0);
				return createElement(ConstraintType.GROUP, ele, c, e, semanticType, multiple, optional);
			}
		}
	ele = lastChild;
	continue;


java.lang.NullPointerException
	at org.eclipse.xtext.GrammarUtil.isOneOrMoreCardinality(GrammarUtil.java:295)
	at org.eclipse.xtext.GrammarUtil.isMultipleCardinality(GrammarUtil.java:291)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxConstraintProvider.createElement(ConcreteSyntaxConstraintProvider.java:334)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxConstraintProvider.createElement(ConcreteSyntaxConstraintProvider.java:319)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxConstraintProvider.createElement(ConcreteSyntaxConstraintProvider.java:353)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxConstraintProvider.getConstraint(ConcreteSyntaxConstraintProvider.java:448)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxConstraintProvider.getConstraints(ConcreteSyntaxConstraintProvider.java:463)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxValidator.validateObject(ConcreteSyntaxValidator.java:104)
	at org.eclipse.xtext.validation.impl.ConcreteSyntaxValidator.validateRecursive(ConcreteSyntaxValidator.java:150)
	at org.eclipse.xtext.parsetree.reconstr.Serializer.serialize(Serializer.java:48)
	at org.eclipse.xtext.parsetree.reconstr.Serializer.serialize(Serializer.java:71)
	at org.eclipse.xtext.parsetree.reconstr.Serializer.serialize(Serializer.java:65)
	at org.eclipse.xtext.junit.AbstractXtextTests.serialize(AbstractXtextTests.java:131)
	at org.cloudsmith.geppetto.pp.dsl.test.TestPuppetResourceExpr.test_Serialize_1(TestPuppetResourceExpr.java:103)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at junit.framework.TestCase.runTest(TestCase.java:168)
	at junit.framework.TestCase.runBare(TestCase.java:134)
	at junit.framework.TestResult$1.protect(TestResult.java:110)
	at junit.framework.TestResult.runProtected(TestResult.java:128)
	at junit.framework.TestResult.run(TestResult.java:113)
	at junit.framework.TestCase.run(TestCase.java:124)
	at junit.framework.TestSuite.runTest(TestSuite.java:232)
	at junit.framework.TestSuite.run(TestSuite.java:227)
	at org.junit.internal.runners.JUnit38ClassRunner.run(JUnit38ClassRunner.java:83)
	at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
	at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
	at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
	at org.eclipse.pde.internal.junit.runtime.RemotePluginTestRunner.main(RemotePluginTestRunner.java:62)
	at org.eclipse.pde.internal.junit.runtime.CoreTestApplication.run(CoreTestApplication.java:23)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.eclipse.equinox.internal.app.EclipseAppContainer.callMethodWithException(EclipseAppContainer.java:587)
	at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:198)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
	at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:369)
	at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:179)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:619)
	at org.eclipse.equinox.launcher.Main.basicRun(Main.java:574)
	at org.eclipse.equinox.launcher.Main.run(Main.java:1407)
	at org.eclipse.equinox.launcher.Main.main(Main.java:1383)