Replace the usage of the depricated \Magento\Framework\Json\EncoderInterface in the CustomerScopeData block,

 - Use \Magento\Framework\Serialize\Serializer\Json instead when dealing with serilization
 - Update test to mirror the change in the main class

Author: dmanners

app/code/Magento/Customer/Block/CustomerScopeData.php

@@ -20,23 +20,23 @@ class CustomerScopeData extends \Magento\Framework\View\Element\Template
     private $storeManager;
 
     /**
-     * @var \Magento\Framework\Json\EncoderInterface
+     * @var \Magento\Framework\Serialize\Serializer\Json
      */
-    private $jsonEncoder;
+    private $serializer;
 
     /**
      * @param \Magento\Framework\View\Element\Template\Context $context
-     * @param \Magento\Framework\Json\EncoderInterface $jsonEncoder
+     * @param \Magento\Framework\Serialize\Serializer\Json $serializer
      * @param array $data
      */
     public function __construct(
         \Magento\Framework\View\Element\Template\Context $context,
-        \Magento\Framework\Json\EncoderInterface $jsonEncoder,
+        \Magento\Framework\Serialize\Serializer\Json $serializer,
         array $data = []
     ) {
         parent::__construct($context, $data);
         $this->storeManager = $context->getStoreManager();
-        $this->jsonEncoder = $jsonEncoder;
+        $this->serializer = $serializer;
     }
 
     /**
@@ -54,11 +54,12 @@ public function getWebsiteId()
     /**
      * Get the invalidation rules json encoded
      *
-     * @return string
+     * @return bool|string
+     * @throws \InvalidArgumentException
      */
-    public function getInvalidationRulesJson()
+    public function getSerializedInvalidationRules()
     {
-        return $this->jsonEncoder->encode(
+        return $this->serializer->serialize(
             [
                 '*' => [
                     'Magento_Customer/js/invalidation-processor' => [

app/code/Magento/Customer/Test/Unit/Block/CustomerScopeDataTest.php

@@ -26,8 +26,8 @@ class CustomerScopeDataTest extends \PHPUnit_Framework_TestCase
     /** @var ScopeConfigInterface|\PHPUnit_Framework_MockObject_MockObject */
     private $scopeConfigMock;
 
-    /** @var \Magento\Framework\Json\EncoderInterface|\PHPUnit_Framework_MockObject_MockObject */
-    private $encoderMock;
+    /** @var \Magento\Framework\Serialize\Serializer\Json|\PHPUnit_Framework_MockObject_MockObject */
+    private $serializerMock;
 
     protected function setUp()
     {
@@ -41,7 +41,7 @@ protected function setUp()
         $this->scopeConfigMock = $this->getMockBuilder(ScopeConfigInterface::class)
             ->getMock();
 
-        $this->encoderMock = $this->getMockBuilder(EncoderInterface::class)
+        $this->serializerMock = $this->getMockBuilder(\Magento\Framework\Serialize\Serializer\Json::class)
             ->getMock();
 
         $this->contextMock->expects($this->exactly(2))
@@ -54,7 +54,7 @@ protected function setUp()
 
         $this->model = new CustomerScopeData(
             $this->contextMock,
-            $this->encoderMock,
+            $this->serializerMock,
             []
         );
     }

app/code/Magento/Customer/view/frontend/templates/js/customer-data/invalidation-rules.phtml

@@ -12,6 +12,6 @@
 <script type="text/x-magento-init">
 <?php
     /* @noEscape */
-    echo $block->getInvalidationRulesJson();
+    echo $block->getSerializedInvalidationRules();
 ?>
 </script>