Link "Add newsletter" not rendered properly

I don't think that's correct, unless we actually cache those per language now and afaik we don't?

Support for title arguments was removed from core, although I don't fully understand the reason, this was the perfect example that needs it :)

title arguments support was removed from YamlDiscovery of plugins. This is a derived plugin afaik that is a totally different situation.

Apparently not, because the title argument is clearly no longer available here. It's using the same class as local actions defined in yaml, so it has the same features.

I guess we need a custom local task plugin class to support this :(

Well there is also the core guideline that proposes to only have one such item... Currently we create multiple in case there are multiple newsletter types...

So... Do we need an intermediate page in case there are multiple newsletter types?

Workaround proposal to deal with the situation:
In case we have only one type we could directly point the user to the node creation form.
In case we have multiple types, we should just point the user to the "Add content" overview...

Its green now, everything is looking good.

1. +++ b/src/Plugin/Derivative/AddSimplenewsIssueActionLinks.php
   @@ -20,17 +20,21 @@ class AddSimplenewsIssueActionLinks extends DeriverBase {
        $node_types = simplenews_get_content_types();
   -    foreach ($node_types as $node_type) {
   +    $node_type = $node_types['simplenews_issue'];
   +    if (count($node_types) == 1) {
   

   Hardcoding that type is wrong, instead, you need to use reset($node_types) if you just have one.

2. +++ b/src/Plugin/Derivative/AddSimplenewsIssueActionLinks.php
   @@ -20,17 +20,21 @@ class AddSimplenewsIssueActionLinks extends DeriverBase {
          $this->derivatives[$node_type] = $base_plugin_definition;
   -      $this->derivatives[$node_type]['title'] = 'Add @label';
   -      $this->derivatives[$node_type]['title_arguments'] = array(
   -        '@label' => $label,
   -      );
   +      $this->derivatives[$node_type]['title'] = t('Add @label', array('@label' => $label));
   

   Calling t() here is wrong, it will not work correctly for transltable sites.

   Still not sure what the correct solution is, maybe using a TranslationWrapper().

3. +++ b/src/Plugin/Derivative/AddSimplenewsIssueActionLinks.php
   @@ -20,17 +20,21 @@ class AddSimplenewsIssueActionLinks extends DeriverBase {
   +    elseif (count($node_types) > 1) {
   +      $base_plugin_definition['route_name'] = 'node.add_page';
   +      $base_plugin_definition['title'] = t('Add content');
   +      $this->derivatives[] = $base_plugin_definition;
   

   Same, t() is wrong.

   Also, add content is wrong and that list will then show all the types, not sure I like that pattern.

   I'd actually suggest to just do the minimal (correct) fix here to get the tests passing again and then think about the multiple local actions problem in a separate issue.

Ok, committed for now, not sure this is correct but we can change later and it works.