fix(query): handle conflicting edge label conditions safely (#2990)

HugeGraph may read LABEL from a ConditionQuery before the query is flattened when optimizing edge traversals. In contradictory label combinations such as inE('created').hasLabel('created', 'look').hasLabel('authored'), the previous intersection logic reused an empty set to mean both 'not initialized yet' and 'already intersected to empty'. That allowed later IN conditions to repopulate the candidate set and raised an Illegal key 'LABEL' with more than one value error instead of returning an empty result.

Track whether the intersection has been initialized independently so an empty intersection remains empty. This keeps the existing protection for true multi-value results, while allowing conflicting label predicates to fall back safely and produce no matches.

Add regression coverage for the low-level ConditionQuery behavior and for the edge traversal scenario from issue #2933, including a match()-based equivalent query to assert consistent zero-count results.

Author: contrueCT

hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/backend/query/ConditionQuery.java

@@ -288,11 +288,13 @@ public <T> T condition(Object key) {
             return value;
         }
 
+        boolean initialized = false;
         Set<Object> intersectValues = InsertionOrderUtil.newSet();
         for (Object value : valuesEQ) {
             List<Object> valueAsList = ImmutableList.of(value);
-            if (intersectValues.isEmpty()) {
+            if (!initialized) {
                 intersectValues.addAll(valueAsList);
+                initialized = true;
             } else {
                 CollectionUtil.intersectWithModify(intersectValues,
                                                    valueAsList);
@@ -301,8 +303,9 @@ public <T> T condition(Object key) {
         for (Object value : valuesIN) {
             @SuppressWarnings("unchecked")
             List<Object> valueAsList = (List<Object>) value;
-            if (intersectValues.isEmpty()) {
+            if (!initialized) {
                 intersectValues.addAll(valueAsList);
+                initialized = true;
             } else {
                 CollectionUtil.intersectWithModify(intersectValues,
                                                    valueAsList);

hugegraph-server/hugegraph-test/src/main/java/org/apache/hugegraph/core/EdgeCoreTest.java

@@ -4646,6 +4646,29 @@ public void testQueryInEdgesOfVertexByLabels() {
         Assert.assertEquals(3L, size);
     }
 
+    @Test
+    public void testQueryInEdgesOfVertexByConflictingLabels() {
+        HugeGraph graph = graph();
+        init18Edges();
+
+        long direct = graph.traversal().V().inE("created")
+                           .hasLabel("created", "look")
+                           .hasLabel("authored")
+                           .count().next();
+        Assert.assertEquals(0L, direct);
+
+        long matched = graph.traversal().V()
+                            .match(__.as("start1")
+                                     .inE("created")
+                                     .as("m1"))
+                            .select("m1")
+                            .hasLabel("created", "look")
+                            .hasLabel("authored")
+                            .count().next();
+        Assert.assertEquals(0L, matched);
+        Assert.assertEquals(matched, direct);
+    }
+
     @Test
     public void testQueryInEdgesOfVertexBySortkey() {
         HugeGraph graph = graph();

hugegraph-server/hugegraph-test/src/main/java/org/apache/hugegraph/unit/core/QueryTest.java

@@ -17,8 +17,10 @@
 
 package org.apache.hugegraph.unit.core;
 
+import org.apache.hugegraph.backend.id.Id;
 import org.apache.hugegraph.backend.id.IdGenerator;
 import org.apache.hugegraph.backend.query.Aggregate.AggregateFunc;
+import org.apache.hugegraph.backend.query.Condition;
 import org.apache.hugegraph.backend.query.ConditionQuery;
 import org.apache.hugegraph.backend.query.IdPrefixQuery;
 import org.apache.hugegraph.backend.query.IdQuery;
@@ -30,6 +32,7 @@
 import org.apache.hugegraph.type.define.HugeKeys;
 import org.junit.Test;
 
+import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 
@@ -45,6 +48,53 @@ public void testOrderBy() {
                             query.orders());
     }
 
+    @Test
+    public void testConditionWithEqAndIn() {
+        Id label1 = IdGenerator.of(1);
+        Id label2 = IdGenerator.of(2);
+
+        ConditionQuery query = new ConditionQuery(HugeType.EDGE);
+        query.eq(HugeKeys.LABEL, label1);
+        query.query(Condition.in(HugeKeys.LABEL,
+                                 ImmutableList.of(label1, label2)));
+
+        Assert.assertEquals(label1, query.condition(HugeKeys.LABEL));
+    }
+
+    @Test
+    public void testConditionWithConflictingEqAndIn() {
+        Id label1 = IdGenerator.of(1);
+        Id label2 = IdGenerator.of(2);
+        Id label3 = IdGenerator.of(3);
+
+        ConditionQuery query = new ConditionQuery(HugeType.EDGE);
+        query.eq(HugeKeys.LABEL, label1);
+        query.eq(HugeKeys.LABEL, label2);
+        query.query(Condition.in(HugeKeys.LABEL,
+                                 ImmutableList.of(label1, label3)));
+
+        Assert.assertNull(query.condition(HugeKeys.LABEL));
+    }
+
+    @Test
+    public void testConditionWithMultipleMatchedInValues() {
+        Id label1 = IdGenerator.of(1);
+        Id label2 = IdGenerator.of(2);
+        Id label3 = IdGenerator.of(3);
+        Id label4 = IdGenerator.of(4);
+
+        ConditionQuery query = new ConditionQuery(HugeType.EDGE);
+        query.query(Condition.in(HugeKeys.LABEL,
+                                 ImmutableList.of(label1, label2, label3)));
+        query.query(Condition.in(HugeKeys.LABEL,
+                                 ImmutableList.of(label1, label2, label4)));
+
+        Assert.assertThrows(IllegalStateException.class,
+                            () -> query.condition(HugeKeys.LABEL),
+                            e -> Assert.assertContains("Illegal key 'LABEL'",
+                                                       e.getMessage()));
+    }
+
     @Test
     public void testToString() {
         Query query = new Query(HugeType.VERTEX);