add x-magento-cache-debug header for production mode use build-in cache

app/code/Magento/PageCache/Model/App/FrontController/BuiltinPlugin.php

@@ -1,12 +1,13 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2014 Adobe
+ * All Rights Reserved.
  */
 namespace Magento\PageCache\Model\App\FrontController;
 
 use Magento\Framework\App\PageCache\NotCacheableInterface;
 use Magento\Framework\App\Response\Http as ResponseHttp;
+use Magento\Framework\App\State;
 
 /**
  * Plugin for processing builtin cache
@@ -111,7 +112,7 @@ protected function addDebugHeaders(ResponseHttp $result)
      */
     protected function addDebugHeader(ResponseHttp $response, $name, $value, $replace = false)
     {
-        if ($this->state->getMode() == \Magento\Framework\App\State::MODE_DEVELOPER) {
+        if ($name == 'X-Magento-Cache-Debug' || $this->state->getMode() == State::MODE_DEVELOPER) {
             $response->setHeader($name, $value, $replace);
         }
     }

app/code/Magento/PageCache/Model/Controller/Result/BuiltinPlugin.php

@@ -1,18 +1,18 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2014 Adobe
+ * All Rights Reserved.
  */
 namespace Magento\PageCache\Model\Controller\Result;
 
-use Magento\PageCache\Model\Config;
+use Laminas\Http\Header\HeaderInterface as HttpHeaderInterface;
 use Magento\Framework\App\PageCache\Kernel;
+use Magento\Framework\App\Response\Http as ResponseHttp;
 use Magento\Framework\App\State as AppState;
-use Magento\Framework\Registry;
 use Magento\Framework\Controller\ResultInterface;
-use Magento\Framework\App\Response\Http as ResponseHttp;
-use Laminas\Http\Header\HeaderInterface as HttpHeaderInterface;
+use Magento\Framework\Registry;
 use Magento\PageCache\Model\Cache\Type as CacheType;
+use Magento\PageCache\Model\Config;
 
 /**
  * Plugin for processing builtin cache
@@ -79,9 +79,8 @@ public function afterRenderResult(ResultInterface $subject, ResultInterface $res
             if ($cacheControlHeader instanceof HttpHeaderInterface) {
                 $response->setHeader('X-Magento-Cache-Control', $cacheControlHeader->getFieldValue());
             }
-
-            $response->setHeader('X-Magento-Cache-Debug', 'MISS', true);
         }
+        $response->setHeader('X-Magento-Cache-Debug', 'MISS', true);
 
         $tagsHeader = $response->getHeader('X-Magento-Tags');
         $tags = [];

app/code/Magento/PageCache/Test/Unit/Model/App/FrontController/BuiltinPluginTest.php

@@ -1,7 +1,7 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2015 Adobe
+ * All Rights Reserved.
  */
 declare(strict_types=1);
 
@@ -130,8 +130,15 @@ function ($arg1, $arg2 = null, $arg3 = null) {
                     }
                 );
         } else {
-            $this->responseMock->expects($this->never())
-                ->method('setHeader');
+            $this->responseMock
+                ->method('setHeader')
+                ->willReturnCallback(
+                    function ($arg1, $arg2 = null, $arg3 = null) {
+                        if ($arg1 === 'X-Magento-Cache-Debug' && $arg2 === 'MISS' && $arg3 === true) {
+                            return null;
+                        }
+                    }
+                );
         }
         $this->responseMock
             ->expects($this->once())
@@ -208,14 +215,11 @@ public function testAroundDispatchReturnsCache($state): void
         $this->stateMock->expects($this->any())
             ->method('getMode')
             ->willReturn($state);
-        if ($state == State::MODE_DEVELOPER) {
-            $this->responseMock->expects($this->once())
-                ->method('setHeader')
-                ->with('X-Magento-Cache-Debug');
-        } else {
-            $this->responseMock->expects($this->never())
-                ->method('setHeader');
-        }
+
+        $this->responseMock->expects($this->once())
+            ->method('setHeader')
+            ->with('X-Magento-Cache-Debug');
+
         $this->assertSame(
             $this->responseMock,
             $this->plugin->aroundDispatch($this->frontControllerMock, $this->closure, $this->requestMock)

app/code/Magento/PageCache/Test/Unit/Model/Controller/Result/BuiltinPluginTest.php

@@ -1,7 +1,7 @@
 <?php
 /**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
+ * Copyright 2015 Adobe
+ * All Rights Reserved.
  */
 declare(strict_types=1);
 
@@ -150,9 +150,15 @@ public function testAfterResultWithPlugin()
         $this->responseMock->expects(static::once())
             ->method('clearHeader')
             ->with('X-Magento-Tags');
-        $this->responseMock->expects(static::once())
+        $this->responseMock->expects(static::any())
             ->method('setHeader')
-            ->with('X-Magento-Tags', 'tag,' . CacheType::CACHE_TAG);
+            ->willReturnCallback(function ($arg1, $arg2 = null, $arg3 = null) {
+                if ($arg1 === 'X-Magento-Cache-Debug' && $arg2 === 'MISS' && $arg3 === true) {
+                    return null;
+                } elseif ($arg1 === 'X-Magento-Tags' && $arg2 === 'tag,' . CacheType::CACHE_TAG) {
+                    return null;
+                }
+            });
         $this->kernelMock->expects(static::once())
             ->method('process')
             ->with($this->responseMock);