Merge main into develop

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

@@ -143,10 +143,7 @@ public Function<ArrayBindingSet, Binding> getDirectGetBinding(String bindingName
 		}
 		return a -> {
 			Value value = a.values[index];
-			if (value == NULL_VALUE) {
-				value = null;
-			}
-			if (value != null) {
+			if (value != null && value != NULL_VALUE) {
 				return new SimpleBinding(bindingName, value);
 			} else {
 				return null;
@@ -416,7 +413,7 @@ public ArrayBindingSetIterator() {
 		@Override
 		public boolean hasNext() {
 			while (index < values.length) {
-				if (values[index] != null) {
+				if (values[index] != null && values[index] != NULL_VALUE) {
 					return true;
 				}
 				index++;
@@ -426,20 +423,10 @@ public boolean hasNext() {
 
 		@Override
 		public Binding next() {
-			while (index < values.length) {
-				if (values[index] != null) {
-					String name = bindingNames[index];
-					Value value = values[index++];
-					if (value == NULL_VALUE) {
-						value = null;
-					}
-					if (value != null) {
-						return new SimpleBinding(name, value);
-					} else {
-						return null;
-					}
-				}
-				index++;
+			if (hasNext()) {
+				String name = bindingNames[index];
+				Value value = values[index++];
+				return new SimpleBinding(name, value);
 			}
 
 			throw new NoSuchElementException();

core/queryalgebra/evaluation/src/main/java/org/eclipse/rdf4j/query/algebra/evaluation/optimizer/ProjectionRemovalOptimizer.java

@@ -79,6 +79,7 @@ private ProjectionFinder() {
 		@Override
 		public void meet(Projection node) throws RuntimeException {
 			super.meet(node);
+
 			VariableFinder findVariables = new VariableFinder();
 			node.visit(findVariables);
 

core/queryalgebra/evaluation/src/test/java/org/eclipse/rdf4j/query/algebra/evaluation/ArrayBindingSetNullHandlingTest.java

@@ -0,0 +1,66 @@
+/**
+ * ******************************************************************************
+ * Copyright (c) 2025 Eclipse RDF4J contributors.
+ *
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Distribution License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/org/documents/edl-v10.php.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ * ******************************************************************************
+ */
+package org.eclipse.rdf4j.query.algebra.evaluation;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.LinkedHashSet;
+import java.util.Set;
+
+import org.eclipse.rdf4j.model.vocabulary.OWL;
+import org.eclipse.rdf4j.query.Binding;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Reproduces a NullPointerException when an ArrayBindingSet contains an explicit null (UNDEF) binding value and is
+ * copied into a QueryBindingSet. Prior to the fix, iterating the ArrayBindingSet could yield a null Binding, which
+ * caused NPE in QueryBindingSet.addBinding.
+ */
+public class ArrayBindingSetNullHandlingTest {
+
+	@Test
+	public void iteratorShouldNotReturnNullBindings() {
+		ArrayBindingSet bs = new ArrayBindingSet("myVar", "unbound", "mappingProp", "const");
+		// Explicitly set an UNDEF/null binding using the direct setter (stores a sentinel NULL_VALUE)
+		bs.getDirectSetBinding("myVar").accept(null, bs);
+		// Add a real binding so iteration has at least one valid element
+		bs.getDirectSetBinding("mappingProp").accept(OWL.EQUIVALENTCLASS, bs);
+
+		for (Binding b : bs) {
+			assertNotNull(b, "iterator must not yield null Binding elements");
+		}
+	}
+
+	@Test
+	public void copyingToQueryBindingSetMustSkipUndefBindings() {
+		ArrayBindingSet bs = new ArrayBindingSet("myVar", "unbound", "mappingProp", "const");
+		// myVar is explicitly present with UNDEF value
+		bs.getDirectSetBinding("myVar").accept(null, bs);
+		// mappingProp has a concrete value
+		bs.getDirectSetBinding("mappingProp").accept(OWL.EQUIVALENTCLASS, bs);
+
+		// Creating a QueryBindingSet from the ArrayBindingSet should not throw
+		QueryBindingSet qbs = assertDoesNotThrow(() -> new QueryBindingSet(bs));
+
+		assertTrue(qbs.hasBinding("mappingProp"));
+		assertEquals(OWL.EQUIVALENTCLASS, qbs.getValue("mappingProp"));
+		// UNDEF binding must not appear in the resulting set
+		assertFalse(qbs.hasBinding("myVar"));
+		assertEquals(1, qbs.size());
+	}
+
+}

core/queryparser/sparql/src/main/java/org/eclipse/rdf4j/query/parser/sparql/WildcardProjectionProcessor.java

@@ -58,8 +58,12 @@ public static void process(ASTOperationContainer container) throws MalformedQuer
 					whereClause.jjtAccept(collector, null);
 
 					Set<ASTSelect> selectClauses = collector.getSelectClauses();
+					// process nested SELECT wildcards deepest-first so inner subqueries are expanded
+					// before their parents collect variables
+					java.util.List<ASTSelect> ordered = new java.util.ArrayList<>(selectClauses);
+					ordered.sort(java.util.Comparator.comparingInt(WildcardProjectionProcessor::depth).reversed());
 
-					for (ASTSelect selectClause : selectClauses) {
+					for (ASTSelect selectClause : ordered) {
 						if (selectClause.isWildcard()) {
 							ASTSelectQuery q = (ASTSelectQuery) selectClause.jjtGetParent();
 
@@ -95,6 +99,16 @@ public static void process(ASTOperationContainer container) throws MalformedQuer
 		}
 	}
 
+	private static int depth(Node n) {
+		int d = 0;
+		Node p = n.jjtGetParent();
+		while (p != null) {
+			d++;
+			p = p.jjtGetParent();
+		}
+		return d;
+	}
+
 	private static void addQueryVars(ASTWhereClause queryBody, Node wildcardNode) throws MalformedQueryException {
 		QueryVariableCollector visitor = new QueryVariableCollector();