GH-4769 ArrayBindingSet access to non existing variables should not fail, but return as if

Signed-off-by: Jerven Bolleman <jerven.bolleman@sib.swiss>

Author: JervenBolleman

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/impl/ArrayBindingBasedQueryEvaluationContext.java

@@ -55,7 +55,7 @@ public final class ArrayBindingBasedQueryEvaluationContext implements QueryEvalu
 	private final BiConsumer<Value, MutableBindingSet>[] setBinding;
 	private final BiConsumer<Value, MutableBindingSet>[] addBinding;
 
-	boolean initialized;
+	private final boolean initialized;
 
 	ArrayBindingBasedQueryEvaluationContext(QueryEvaluationContext context, String[] allVariables) {
 		assert new HashSet<>(Arrays.asList(allVariables)).size() == allVariables.length;
@@ -109,7 +109,12 @@ public Predicate<BindingSet> hasBinding(String variableName) {
 
 		assert variableName != null && !variableName.isEmpty();
 		Function<ArrayBindingSet, Boolean> directHasVariable = defaultArrayBindingSet.getDirectHasBinding(variableName);
-		return new HasBinding(variableName, directHasVariable);
+		if (directHasVariable != null) {
+			return new HasBinding(variableName, directHasVariable);
+		} else {
+			// If the variable is not in the default set, it can never be part of this array binding
+			return (bs) -> false;
+		}
 	}
 
 	static private class HasBinding implements Predicate<BindingSet> {
@@ -147,16 +152,19 @@ public Function<BindingSet, Binding> getBinding(String variableName) {
 
 		Function<ArrayBindingSet, Binding> directAccessForVariable = defaultArrayBindingSet
 				.getDirectGetBinding(variableName);
-		return (bs) -> {
-			if (bs.isEmpty()) {
-				return null;
-			}
-			if (bs instanceof ArrayBindingSet) {
-				return directAccessForVariable.apply((ArrayBindingSet) bs);
-			} else {
-				return bs.getBinding(variableName);
-			}
-		};
+		if (directAccessForVariable != null) {
+			return (bs) -> {
+				if (bs instanceof ArrayBindingSet) {
+					return directAccessForVariable.apply((ArrayBindingSet) bs);
+				} else if (bs.isEmpty()) {
+					return null;
+				} else {
+					return bs.getBinding(variableName);
+				}
+			};
+		} else {
+			return (bs) -> null;
+		}
 	}
 
 	@Override
@@ -171,7 +179,12 @@ public Function<BindingSet, Value> getValue(String variableName) {
 
 		Function<ArrayBindingSet, Value> directAccessForVariable = defaultArrayBindingSet
 				.getDirectGetValue(variableName);
-		return new ValueGetter(variableName, directAccessForVariable);
+		if (directAccessForVariable != null) {
+			return new ValueGetter(variableName, directAccessForVariable);
+		} else {
+			// If the variable is not in the default set, it can never be part of this array binding
+			return (bs) -> null;
+		}
 	}
 
 	private static class ValueGetter implements Function<BindingSet, Value> {
@@ -210,13 +223,17 @@ public BiConsumer<Value, MutableBindingSet> setBinding(String variableName) {
 
 		BiConsumer<Value, ArrayBindingSet> directAccessForVariable = defaultArrayBindingSet
 				.getDirectSetBinding(variableName);
-		return (val, bs) -> {
-			if (bs instanceof ArrayBindingSet) {
-				directAccessForVariable.accept(val, (ArrayBindingSet) bs);
-			} else {
-				bs.setBinding(variableName, val);
-			}
-		};
+		if (directAccessForVariable != null) {
+			return (val, bs) -> {
+				if (bs instanceof ArrayBindingSet) {
+					directAccessForVariable.accept(val, (ArrayBindingSet) bs);
+				} else {
+					bs.setBinding(variableName, val);
+				}
+			};
+		} else {
+			return (val, bs) -> bs.setBinding(variableName, val);
+		}
 	}
 
 	@Override
@@ -231,13 +248,17 @@ public BiConsumer<Value, MutableBindingSet> addBinding(String variableName) {
 
 		BiConsumer<Value, ArrayBindingSet> wrapped = defaultArrayBindingSet
 				.getDirectAddBinding(variableName);
-		return (val, bs) -> {
-			if (bs instanceof ArrayBindingSet) {
-				wrapped.accept(val, (ArrayBindingSet) bs);
-			} else {
-				bs.addBinding(variableName, val);
-			}
-		};
+		if (wrapped != null) {
+			return (val, bs) -> {
+				if (bs instanceof ArrayBindingSet) {
+					wrapped.accept(val, (ArrayBindingSet) bs);
+				} else {
+					bs.addBinding(variableName, val);
+				}
+			};
+		} else {
+			return (val, bs) -> bs.addBinding(variableName, val);
+		}
 	}
 
 	@Override