removed duplicated joins when using joinWith and via relations

fixes #2650

framework/db/ActiveQuery.php

@@ -414,6 +414,14 @@ class ActiveQuery extends Query implements ActiveQueryInterface
             $this->with($with);
         }
 
+        // remove duplicated joins added by joinWithRelations that may be added
+        // e.g. when joining a relation and a via relation at the same time
+        $uniqueJoins = [];
+        foreach($this->join as $j) {
+            $uniqueJoins[serialize($j)] = $j;
+        }
+        $this->join = array_values($uniqueJoins);
+
         if (!empty($join)) {
             // append explicit join to joinWith()
             // https://github.com/yiisoft/yii2/issues/2880

tests/unit/framework/db/ActiveRecordTest.php

@@ -426,7 +426,16 @@ class ActiveRecordTest extends DatabaseTestCase
         $this->assertEquals(1, $customers[1]->id);
         $this->assertTrue($customers[0]->isRelationPopulated('orders'));
         $this->assertTrue($customers[1]->isRelationPopulated('orders'));
+    }
 
+    /**
+     * This query will do the same join twice, ensure duplicated JOIN gets removed
+     * https://github.com/yiisoft/yii2/pull/2650
+     */
+    public function testJoinWithVia()
+    {
+        Order::getDb()->getQueryBuilder()->separator = "\n";
+        Order::find()->joinWith('itemsInOrder1')->joinWith('items')->all();
     }
 
     public function testInverseOf()