Follow-up for #2481453: ensure the 'url.query_args': MainContentViewSubscriber::WRAPPER_FORMAT cache context is set

+++ b/core/modules/menu_link_content/src/Tests/MenuLinkContentTranslationUITest.php
@@ -20,7 +20,7 @@ class MenuLinkContentTranslationUITest extends ContentTranslationUITestBase {
-  protected $defaultCacheContexts = ['languages:language_interface', 'theme', 'user.permissions', 'user.roles:authenticated'];
+  protected $defaultCacheContexts = ['languages:language_interface', 'theme', 'url.query_args:_wrapper_format', 'user.permissions', 'user.roles:authenticated'];

Question: So we need to not change that many places, because we use url.query_args in other places already?

Do we need some explicit test coverage for this issue? I mean adding the expected cache contexts is one thing, but having a real case is another.

To be honest it feels like the code could still be broken in theory now after reading your latest comment. We could for sure write a test wrapper which implements the CacheableResponseInterface

#2476407: Use CacheableResponseInterface to determine which responses should be cached will also introduce a CacheableJsonResponse that also implements CacheableResponseInterface. So adding a test could be a followup to that issue?

+    $this->drupalGet('');
+    $this->assertCacheContext('url.query_args:' . MainContentViewSubscriber::WRAPPER_FORMAT);
+    $this->drupalGet('', ['query' => [MainContentViewSubscriber::WRAPPER_FORMAT =>  'json']]);
+    $this->assertCacheContext('url.query_args:' . MainContentViewSubscriber::WRAPPER_FORMAT);

If we would have missed that cache context we would have served the wrong kind of context, therefore I think we should have an integration test coverage
which ensures that you can cache two different wrapper formats and get different output.

Cool. Thank you!

Committed/pushed to 8.0.x, thanks!