Error <Cannot assign null to property CommerceGuys\Addressing\Country\CountryRepository::$defaultLocale> after version 2 upgrade

This is the crashing code:

  public function __construct(CacheBackendInterface $cache, LanguageManagerInterface $language_manager) {
    parent::__construct();

    $this->cache = $cache;
    // The getCurrentLanguage() fallback is a workaround for core bug #2684873.
    $language = $language_manager->getConfigOverrideLanguage() ?: $language_manager->getCurrentLanguage();
    $this->defaultLocale = $language->getId();
  }

It should not be possible for $language->getId() to be null. It indicates something very wrong with your site (or a core bug).

I suggest adding some debug code here to see which language is used (config override or current language) and what the value of $language is.

Thanks @bojanz.
MR is created.

VladimirAus → changed the visibility of the branch 3425922-error-cannot-assign to hidden.

VladimirAus → changed the visibility of the branch 3425922-error-cannot-assign to hidden.

VladimirAus → changed the visibility of the branch 3425922-error-cannot-assign to hidden.

VladimirAus → changed the visibility of the branch 3425922-error-cannot-assign to hidden.

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@VladimirAus
Can you give us the output of this:

    var_dump($language_manager->getConfigOverrideLanguage());
   var_dump($language_manager->getConfigOverrideLanguage()->getId());

From what I can see, core issue #2684873: ConfigurableLanguageManager::getConfigOverrideLanguage() returns NULL → was fixed ages ago (Drupal 8.3), so our logic should be as simple as:

    $this->defaultLocale = $language_manager->getConfigOverrideLanguage()->getId();

According to the interfaces, getConfigOverrideLanguage() always returns a language, and getId() always returns a string, so a crash should be impossible.

Let me have a look @bojanz