Admin theme for translation tabs just works for nodes

For example, try custom menu links.

this was fixed in part 4 #2301317: MenuLinkNG part4: Conversion
with

diff --git a/core/modules/menu_link_content/menu_link_content.routing.yml b/core/modules/menu_link_content/menu_link_content.routing.yml
index f96b22d..cebc134 100644
--- a/core/modules/menu_link_content/menu_link_content.routing.yml
+++ b/core/modules/menu_link_content/menu_link_content.routing.yml
@@ -11,6 +11,8 @@ menu_link_content.link_edit:
   defaults:
     _entity_form: 'menu_link_content.default'
     _title: 'Edit menu link'
+  options:
+    _admin_route: TRUE
   requirements:
     _entity_access: 'menu_link_content.update'

that might have been adding the wrong relate issue.
maybe meant to add #2276387: Translate routes should properly inherit admin path use from edit route

ok. when we fix it the correct way, we should check to see if the similar fix for nodes in 2276387 can be undone also.

Shortcuts have the same problem, see #2320037: Non-fieldable entities (with only base fields) cannot be configured translatable, eg. shortcuts which includes the same workaround that is in menu_link_content.

Does any of the existing ones have tests, besides node translation pages?

Duh, not going to work. Instead of service priorities, we should set event priorities. This works.

Now with tests. The interdiff is the TEST ONLY patch. It should not fail since we have the hardcoded admin page designation in the route. Once we remove that, but without fixing the priorities, it will not work (see TEST ONLY WILL FAIL patch). The fix and test overall is in the 11 patch.

Makes sense to me.

+++ b/core/modules/content_translation/src/Routing/ContentTranslationRouteSubscriber.php
@@ -168,7 +168,9 @@ protected function alterRoutes(RouteCollection $collection) {
+    // Should run after AdminRouteSubscriber so the routes can inherit admin
+    // status of the edit routes on entities. Therefore priority -201.
+    $events[RoutingEvents::ALTER] = array('onAlterRoutes', -201);

How about -210 so there is a gap between AdminRouteSubscriber and ContentTranslationRouteSubscriber?

Sure thing. The only side effect is that requires the param converter route subscriber to be changed as well since otherwise they are the same priority and the params are not yet converted when access tries to deal with them (content translation comes before paramconverter in the alphabet).

Better said, the content translation routes would not have param converters applied properly if the content translation routes are added after the param converter altering is done. (This shows in severe test fails if we don't change the param converter priority).

Adding blocker tag since this postpones #2320037: Non-fieldable entities (with only base fields) cannot be configured translatable, eg. shortcuts.

Was random test fail.

Committed 3254a1a and pushed to 8.0.x. Thanks!

Yay, thanks!