MAGETWO-69378: #4272: v2.0.4 Credit memos with adjustment fees cannot be fully refunded with a second credit memo #9715

Author: ishakhsuvarov

app/code/Magento/Sales/Model/Order.php

@@ -618,7 +618,12 @@ public function canCreditmemo()
          * for this we have additional diapason for 0
          * TotalPaid - contains amount, that were not rounded.
          */
-        if (abs($this->priceCurrency->round($this->getTotalPaid()) - $this->getTotalRefunded()) < .0001) {
+        $totalRefunded = $this->priceCurrency->round($this->getTotalPaid()) - $this->getTotalRefunded();
+        if (abs($totalRefunded) < .0001) {
+            return false;
+        }
+        // Case when Adjustment Fee (adjustment_negative) has been used for first creditmemo
+        if (abs($totalRefunded - $this->getAdjustmentNegative()) < .0001) {
             return false;
         }
 

app/code/Magento/Sales/Test/Unit/Model/OrderTest.php

@@ -357,6 +357,34 @@ public function testCanNotCreditMemoWithTotalNull()
         $this->assertFalse($this->order->canCreditmemo());
     }
 
+    public function testCanNotCreditMemoWithAdjustmentNegative()
+    {
+        $totalPaid = 100;
+        $adjustmentNegative = 10;
+        $totalRefunded = 90;
+
+        $this->order->setTotalPaid($totalPaid);
+        $this->order->setTotalRefunded($totalRefunded);
+        $this->order->setAdjustmentNegative($adjustmentNegative);
+        $this->priceCurrency->expects($this->once())->method('round')->with($totalPaid)->willReturnArgument(0);
+        
+        $this->assertFalse($this->order->canCreditmemo());
+    }
+
+    public function testCanCreditMemoWithAdjustmentNegativeLowerThanTotalPaid()
+    {
+        $totalPaid = 100;
+        $adjustmentNegative = 9;
+        $totalRefunded = 90;
+
+        $this->order->setTotalPaid($totalPaid);
+        $this->order->setTotalRefunded($totalRefunded);
+        $this->order->setAdjustmentNegative($adjustmentNegative);
+        $this->priceCurrency->expects($this->once())->method('round')->with($totalPaid)->willReturnArgument(0);
+
+        $this->assertTrue($this->order->canCreditmemo());
+    }
+
     /**
      * @param string $state
      *