The transform method throws a ClassCastException when working with jo…

…inFetch since 4.4.0 (#534)

* ported fix for #3264 querydsl/querydsl#3264
from https://github.com/aasyspl/querydsl

* test for regression querydsl/querydsl#3264

* Allow test to throw exceptions when needed

* Move logic for tuple creation to TupleUtils

---------

Co-authored-by: sapolinarski <[email protected]>
Co-authored-by: Marvin Froeder <[email protected]>

querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericCollection.java

@@ -20,6 +20,7 @@
 import com.querydsl.core.types.FactoryExpression;
 import com.querydsl.core.types.FactoryExpressionUtils;
 import com.querydsl.core.types.Projections;
+import com.querydsl.core.util.TupleUtils;
 import java.util.Collection;
 import java.util.Objects;
 import java.util.function.Supplier;
@@ -60,8 +61,10 @@ public RES transform(FetchableQuery<?, ?> query) {
     GroupImpl group = null;
     K groupId = null;
     while (iter.hasNext()) {
+      Tuple tuple = TupleUtils.toTuple(iter.next(), expressions);
       @SuppressWarnings("unchecked") // This type is mandated by the key type
-      K[] row = (K[]) iter.next().toArray();
+      K[] row = (K[]) tuple.toArray();
+      // end of workaround
       if (group == null) {
         group = new GroupImpl(groupExpressions, maps);
         groupId = row[0];

querydsl-core/src/main/java/com/querydsl/core/group/GroupByGenericMap.java

@@ -20,6 +20,7 @@
 import com.querydsl.core.types.FactoryExpression;
 import com.querydsl.core.types.FactoryExpressionUtils;
 import com.querydsl.core.types.Projections;
+import com.querydsl.core.util.TupleUtils;
 import java.util.Map;
 import java.util.function.Supplier;
 
@@ -57,8 +58,11 @@ public RES transform(FetchableQuery<?, ?> query) {
     CloseableIterator<Tuple> iter = query.select(expr).iterate();
     try {
       while (iter.hasNext()) {
+        Tuple tuple = TupleUtils.toTuple(iter.next(), expressions);
+
         @SuppressWarnings("unchecked") // This type is mandated by the key type
-        K[] row = (K[]) iter.next().toArray();
+        K[] row = (K[]) tuple.toArray();
+        // end of workaround
         K groupId = row[0];
         GroupImpl group = (GroupImpl) groups.get(groupId);
         if (group == null) {

querydsl-core/src/main/java/com/querydsl/core/group/GroupByIterate.java

@@ -20,6 +20,7 @@
 import com.querydsl.core.types.FactoryExpression;
 import com.querydsl.core.types.FactoryExpressionUtils;
 import com.querydsl.core.types.Projections;
+import com.querydsl.core.util.TupleUtils;
 import java.util.NoSuchElementException;
 import java.util.Objects;
 
@@ -73,8 +74,12 @@ public V next() {
         }
 
         while (iter.hasNext()) {
+          // workaround from https://github.com/querydsl/querydsl/issues/3264
+          Tuple tuple = TupleUtils.toTuple(iter.next(), expressions);
+
           @SuppressWarnings("unchecked") // This type is mandated by the key type
-          K[] row = (K[]) iter.next().toArray();
+          K[] row = (K[]) tuple.toArray();
+          // end of workaround
           if (group == null) {
             group = new GroupImpl(groupExpressions, maps);
             groupId = row[0];

querydsl-core/src/main/java/com/querydsl/core/group/GroupByMap.java

@@ -20,6 +20,7 @@
 import com.querydsl.core.types.FactoryExpression;
 import com.querydsl.core.types.FactoryExpressionUtils;
 import com.querydsl.core.types.Projections;
+import com.querydsl.core.util.TupleUtils;
 import java.util.LinkedHashMap;
 import java.util.Map;
 
@@ -51,8 +52,11 @@ public Map<K, V> transform(FetchableQuery<?, ?> query) {
     }
     try (CloseableIterator<Tuple> iter = query.select(expr).iterate()) {
       while (iter.hasNext()) {
+        Tuple tuple = TupleUtils.toTuple(iter.next(), expressions);
+
         @SuppressWarnings("unchecked") // This type is mandated by the key type
-        K[] row = (K[]) iter.next().toArray();
+        K[] row = (K[]) tuple.toArray();
+        // end of workaround
         K groupId = row[0];
         GroupImpl group = (GroupImpl) groups.get(groupId);
         if (group == null) {

querydsl-core/src/main/java/com/querydsl/core/util/TupleUtils.java

@@ -0,0 +1,22 @@
+package com.querydsl.core.util;
+
+import com.querydsl.core.Tuple;
+import com.querydsl.core.types.Expression;
+import com.querydsl.core.types.Projections;
+
+/** TupleUtils provides tuple related utility functionality */
+public final class TupleUtils {
+
+  public static Tuple toTuple(Object next, Expression<?>[] expressions) {
+    // workaround from https://github.com/querydsl/querydsl/issues/3264
+    Tuple tuple;
+    if (next instanceof Tuple) {
+      tuple = (Tuple) next;
+    } else if (next instanceof Object[]) {
+      tuple = Projections.tuple(expressions).newInstance((Object[]) next);
+    } else {
+      throw new IllegalArgumentException(String.format("Could not translate %s into tuple", next));
+    }
+    return tuple;
+  }
+}

querydsl-jpa/src/test/java/com/querydsl/jpa/HibernateBase.java

@@ -14,10 +14,14 @@
 package com.querydsl.jpa;
 
 import static org.junit.Assert.*;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 
 import com.mysema.commons.lang.CloseableIterator;
 import com.querydsl.core.DefaultQueryMetadata;
+import com.querydsl.core.Target;
 import com.querydsl.core.Tuple;
+import com.querydsl.core.group.GroupBy;
+import com.querydsl.core.testutil.ExcludeIn;
 import com.querydsl.core.types.EntityPath;
 import com.querydsl.core.types.Expression;
 import com.querydsl.jpa.domain.Cat;
@@ -158,4 +162,17 @@ public void createQuery3() {
       assertTrue(row instanceof String);
     }
   }
+
+  @Test
+  @ExcludeIn(Target.DERBY)
+  public void createQuery4() {
+    assertDoesNotThrow(
+        () ->
+            query()
+                .from(cat)
+                .leftJoin(cat.kittens)
+                .fetchJoin()
+                .distinct()
+                .transform(GroupBy.groupBy(cat.id).as(cat)));
+  }
 }