Making possible to define configuration by environment:

- Add new file config_env.php into the config pool
- Add CONFIG_ENV_MODE in env.php to be able to specify the system environment

Author: jalogut

lib/internal/Magento/Framework/App/DeploymentConfig/Reader.php

@@ -19,6 +19,8 @@
  */
 class Reader
 {
+    const CONFIG_ENV_MODE = 'CONFIG_ENV_MODE';
+
     /**
      * @var DirectoryList
      */
@@ -41,6 +43,11 @@ class Reader
      */
     private $files;
 
+    /**
+     * @var string
+     */
+    private $configEnvMode;
+
     /**
      * Constructor
      *
@@ -92,6 +99,11 @@ public function getFiles()
      */
     public function load($fileKey = null)
     {
+        $configEnvMode = $this->getConfigEnvMode();
+        if ($configEnvMode) {
+            putenv(self::CONFIG_ENV_MODE . "=" . $configEnvMode);
+        }
+
         $path = $this->dirList->getPath(DirectoryList::CONFIG);
         $fileDriver = $this->driverPool->getDriver(DriverPool::FILE);
         $result = [];
@@ -120,6 +132,27 @@ public function load($fileKey = null)
         return $result ?: [];
     }
 
+    /**
+     * Get CONFIG_ENV_MODE from env.php file configuration
+     *
+     * @return string
+     */
+    private function getConfigEnvMode() : string
+    {
+        if (!isset($this->configEnvMode)) {
+            $configPath = $this->dirList->getPath(DirectoryList::CONFIG);
+            $fileDriver = $this->driverPool->getDriver(DriverPool::FILE);
+            $envFile = $configPath . '/' . $this->configFilePool->getPath(ConfigFilePool::APP_ENV);
+            if ($fileDriver->isExists($envFile)) {
+                $config = include $envFile;
+                $this->configEnvMode = $config[self::CONFIG_ENV_MODE] ?? "";
+            } else {
+                $this->configEnvMode = "";
+            }
+        }
+        return $this->configEnvMode;
+    }
+
     /**
      * Loads the configuration file.
      *

lib/internal/Magento/Framework/Config/File/ConfigFilePool.php

@@ -13,6 +13,7 @@
 class ConfigFilePool
 {
     const APP_CONFIG = 'app_config';
+    const APP_CONFIG_ENV = 'app_config_env';
     const APP_ENV = 'app_env';
 
     /**
@@ -32,6 +33,7 @@ class ConfigFilePool
      */
     private $applicationConfigFiles = [
         self::APP_CONFIG => 'config.php',
+        self::APP_CONFIG_ENV => 'config_env.php',
         self::APP_ENV => 'env.php',
     ];
 

lib/internal/Magento/Framework/Config/Test/Unit/File/ConfigFilePoolTest.php

@@ -27,6 +27,7 @@ public function testGetPaths()
     {
         $expected['new_key'] = 'new_config.php';
         $expected[ConfigFilePool::APP_CONFIG] = 'config.php';
+        $expected[ConfigFilePool::APP_CONFIG_ENV] = 'config_env.php';
         $expected[ConfigFilePool::APP_ENV] = 'env.php';
 
         $this->assertEquals($expected, $this->configFilePool->getPaths());