Environment variables set in _config.php are not picked up in .yml

[AljosaB]

Affected Version

SS 4.3.3

Description

Environment variables set in /app/_config.php with Environment::setEnv or via EnvironmentLoader are not available in .yml config. In example below all links point to www.ccc.com instead of www.aaa.com or www.bbb.com

Director.alternate_base_url is used only for example (couldn't find a better one).

Steps to Reproduce

/app/_config.php

<?php

use SilverStripe\Core\EnvironmentLoader;
use SilverStripe\Core\Environment;

Environment::setEnv('BBB', 'true');

// https://docs.silverstripe.org/en/4/getting_started/environment_management/#including-an-extra-env-file
$env = BASE_PATH . '/app/.env';
$loader = new EnvironmentLoader();
$loader->loadFile($env);

/app/.env

AAA=true

/app/_config/mysite.yml

---
Name: myproject
---
SilverStripe\Core\Manifest\ModuleManifest:
  project: app

SilverStripe\Control\Director:
  alternate_base_url: 'http://www.ccc.com'

---
Only:
  envvarset: 'AAA'
---
SilverStripe\Control\Director:
  alternate_base_url: 'http://www.aaa.com'

---
Only:
  envvarset: 'BBB'
---
SilverStripe\Control\Director:
  alternate_base_url: 'http://www.bbb.com'

[chillu]

This is a documented feature, and pretty crucial to many infrastructure setups, so I'm raising prio to high. https://docs.silverstripe.org/en/4/getting_started/environment_management/

[azt3k]

I have run into this issue for the first time in 4.10.4, previously this was working on other 4.x releases