MAGETWO-56695: Paypal checkout not possible with products that have custom options #5938 - for 2.1

Author: ameysar

app/code/Magento/Catalog/Model/Product.php

@@ -1905,13 +1905,14 @@ public function addOption(Product\Option $option)
      */
     public function getOptionById($optionId)
     {
-        /** @var \Magento\Catalog\Model\Product\Option $option */
-        foreach ($this->getOptions() as $option) {
-            if ($option->getId() == $optionId) {
-                return $option;
+        if (is_array($this->getOptions())) {
+            /** @var \Magento\Catalog\Model\Product\Option $option */
+            foreach ($this->getOptions() as $option) {
+                if ($option->getId() == $optionId) {
+                    return $option;
+                }
             }
         }
-
         return null;
     }
 

app/code/Magento/Catalog/Test/Unit/Model/ProductTest.php

@@ -1332,4 +1332,27 @@ public function testGetTypeId()
         $this->model->setTypeId('typeId');
         $this->model->getTypeInstance();
     }
+
+    public function testGetOptionById()
+    {
+        $optionId = 100;
+        $optionMock = $this->getMock(\Magento\Catalog\Model\Product\Option::class, [], [], '', false);
+        $this->model->setOptions([$optionMock]);
+        $optionMock->expects($this->once())->method('getId')->willReturn($optionId);
+        $this->assertEquals($optionMock, $this->model->getOptionById($optionId));
+    }
+
+    public function testGetOptionByIdWithWrongOptionId()
+    {
+        $optionId = 100;
+        $optionMock = $this->getMock(\Magento\Catalog\Model\Product\Option::class, [], [], '', false);
+        $this->model->setOptions([$optionMock]);
+        $optionMock->expects($this->once())->method('getId')->willReturn(200);
+        $this->assertNull($this->model->getOptionById($optionId));
+    }
+
+    public function testGetOptionByIdForProductWithoutOptions()
+    {
+        $this->assertNull($this->model->getOptionById(100));
+    }
 }