Multilingual dropbutton links do not contain correct language identifier

I meet exactly the same problem with Bootstrap / Dropdown language.
This tips didn't work for me.
https://www.drupal.org/project/dropdown_language/issues/2886977#comment-...

Could you please do something about it?

Thank you !

I pretty sure this is a combination of both Dropdown Language and Bootstrap.

According to https://drupal.stackexchange.com/questions/195545/custom-language-switch..., Dropdown Language should be using a deriver, which it's currently not. See:

\Drupal\language\Plugin\Block\LanguageBlock
\Drupal\language\Plugin\Derivative\LanguageBlock

It could even be a semi-core bug in \Drupal\language\Plugin\LanguageNegotiation\LanguageNegotiationUrl::getLanguageSwitchLinks perhaps?

All it does is clone the URL object, but it never sets the language on it (which may be handled by some deriver magic... I'm not sure).

Regardless, I think just checking for the language property in the link and then setting it on the Url object in the theme as a final backup should be enough.

I'll commit a fix shortly.

Applied the patch given by markcarver & removed the below if condition in the BootstrapDropdown.php it works like a charm.

if (empty($element['url']->getOption('language'))) {
     $element['url']->setOption('language', $element['language']);
}

to

$element['url']->setOption('language', $element['language']);

@sriman is coming from #2868100: Editing translations wrong redirect.

I'm not convinced removing the if statement is the right solution. It exists to ensure the theme doesn't override an explicitly set language option on a URL, which is coming from core/contrib.