Move controller derivation to route enhancers (and just that)

#1 no longer applies on HEAD.

AJAX on hook_menu() routes still fails on this, just as it did in #1938980-22: Fix Ajax system; the last remnants of the old API must be swept away. Here's a fix to our tests so that bot catches it. Will follow up here with a fix to the patch to make them pass.

This fixes the failures caused by this issue. However, there are still AJAX asset delivery failures that exist in HEAD, but not previously caught by bot due to its lack of sending the header added in #5. With that header added, that bug is now being caught by bot. The fix for it is being worked on in #1941288: Regression: ajaxPageState not being updated with AjaxResponse, assets (js/css) being added twice.

This just applies the code fixes in #6, but without the test fixes in #5, in case we want to not hold this issue up on #1941288: Regression: ajaxPageState not being updated with AjaxResponse, assets (js/css) being added twice.

RouteProcessorSubscriber in HEAD runs on all requests. #4 replaces that with enhancers that run only on new router routes. Therefore, it breaks system/ajax requests by not running AjaxEnhancer on it. #7 fixes that (see the #6 interdiff).

To clarify, this is the interdiff from #4 to #7. All it does is change AjaxEnhancer to apply to legacy routes as well, to match the existing behavior in HEAD per #9.

The fails in #6 are the same as the fails in #1967036: WebTestBase::drupalGetAJAX() and WebTestBase::drupalPostAJAX() don't set the Accept header needed for content negotiation, and are a preexisting bug in HEAD, so we can punt to that issue to fix them.

The additional fails that are in #5 demonstrate that we do have adequate tests (once we fix drupalPostAjax() itself in that other issue) that would have caught #4 having a bug (including the impact to Field UI originally reported in #1938980-22: Fix Ajax system; the last remnants of the old API must be swept away that required us to rollback that initial commit). That these tests do not fail in #6 demonstrate that the fix (same one in both #6 and #7) works.

As long as Crell approves this interdiff, I think #7 can be RTBC'd.

+1

No longer applies. :(

But Alex just walked me through it and I'm comfortable committing when it's ready. Seems good to separate these out into pluggable route enhancers rather than a huge gunky bunch of ifs/elses.

One thing I'd be curious to know is if we can un-comment the test at this point now that we've added the missing reference to legacy blah blah thing.

It only conflicted because #1847768: Remove ip_address() added reverse_proxy_subscriber right where this patch was moving stuff around, no actual conflicts.

Trying with an without that test commented out.

+++ b/core/lib/Drupal/Core/Routing/Enhancer/AjaxEnhancer.php
@@ -0,0 +1,43 @@
+    if (empty($defaults['_content']) && $this->negotiation->getContentType($request) == 'drupal_ajax') {

The reason the uncommented test fails is that the above is checking that _content is empty instead of _controller being empty. The other enhancers check for empty _controller, which makes more sense, because the idea is that you want to apply a default _controller when there isn't one already. However, the above line is the same as what is already in the RouteProcessorSubscriber being removed, and this issue is only about moving that code, not fixing it. #1938980: Fix Ajax system; the last remnants of the old API must be swept away is the issue in which that line can be fixed, once we fix our other HEAD problems involving competing AJAX systems and simpletest testing the wrong one.

So, RTBC for the green patch in #14.

Some minor nits... would love to unblock this to get stuff moving...

+++ b/core/lib/Drupal/Core/Routing/Enhancer/AjaxEnhancer.phpundefined
@@ -0,0 +1,43 @@
+  /**
+   * Constructs a new \Drupal\Core\Routing\Enhancer\AjaxEnhancer object.
+   */

Missing param...

+++ b/core/lib/Drupal/Core/Routing/Enhancer/AjaxEnhancer.phpundefined
@@ -0,0 +1,43 @@
+   * Implements \Symfony\Cmf\Component\Routing\Enhancer\RouteEnhancerInterface::enhance()

+++ b/core/lib/Drupal/Core/Routing/Enhancer/FormEnhancer.phpundefined
@@ -0,0 +1,43 @@
+   * Implements \Symfony\Cmf\Component\Routing\Enhancer\RouteEnhancerInterface::enhance()

+++ b/core/lib/Drupal/Core/Routing/Enhancer/PageEnhancer.phpundefined
@@ -0,0 +1,43 @@
+   * Implements \Symfony\Cmf\Component\Routing\Enhancer\RouteEnhancerInterface::enhance()

@inheritdoc

+++ b/core/lib/Drupal/Core/Routing/Enhancer/FormEnhancer.phpundefined
@@ -0,0 +1,43 @@
+  /**
+   * Constructs a new \Drupal\Core\Routing\Enhancer\FormEnhancer object.
+   */

Missing param

+++ b/core/lib/Drupal/Core/Routing/Enhancer/PageEnhancer.phpundefined
@@ -0,0 +1,43 @@
+  /**
+   * Constructs a new \Drupal\Core\Routing\Enhancer\PageEnhancer object.
+   */

Missing param

+++ b/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/TestContent.phpundefined
@@ -0,0 +1,19 @@
+  public function test1() {
+    return 'abcde';
+  }

Missing doc block

As promised on IRC

Committed 99b39dc and pushed to 8.x. Thanks!

Change notice for review is here: https://drupal.org/node/2012100

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