Authcache Comment incompatible with Edit Limit module

Hey, I'm trying to reproduce this with bartik (standard D7 theme). This is what I did:

1. Install D7 + devel + authcache, configure authcache for frontend roles
2. Generate users, nodes and comments using devel generate
3. Install ajax comments
4. Enable ajax comments on all content types
5. Verify that pages are served from the cache for frontend users
6. Verify that comments are posted using XHR

With this setup I'm unable to reproduce any JavaScript errors. Am I missing some crucial config, or could it be a theme related issue?

Ok, do you know a way to reproduce the problem with a minimum number of components?

I took a look at the edit limit module and the linked patches. If there is an edit limit configured for comments, then the backend code appends a string to the edit link with the time remaining for a user to edit his/her comment. The remaining time is calculated using $time_limit - REQUES_TIME. The frontend code parses this string and starts a timeout. If this timeout is reached the edit link is hidden.

The problem with this approach is that for cached pages this timeout will always be the same. Assume there is an edit limit of 10 minutes. If a page was rendered and cached at 12:00, the frontend timeout will expire at 12:10. A subsequent request on 12:05 to the same page will deliver the page from the cache. Since the timeout displayed on the page is relative, the frontend code will set a timeout of 10 minutes and the edit link will only be removed at 12:15. Obviously you only have this problem in the frontend. The access checks in the backend will always work with fresh data. This discrepancy could be detrimental to user experience though.

In combination with all the other issues / patches you encountered, I recommend to just create a custom module which only implements the features for edit link you need in a cache friendly way.

In order to make the frontend code cache aware, you might want to do the following:

1. In the backend add a data-property to the edit-link element which specifies the absolute time when it should disappear. Either use unix timestamps or something which is properly interpreted by moment.js
2. In the frontend code parse this timestamp and compute the relative timeout string in regular intervals.
3. Whenever the timestamp is reached, hide the edit link.

There are multiple possibilities to implement the functionality in the backend. Maybe it is more user-friendly to just make the comment edit form read-only and display a message that the timeout has been reached instead of messing with access callbacks. Who knows...

Also since the edit link project is not maintained (last release in 2013) and only has very few users, I'm quite reluctant to accept modifications specific to this module. Also the suggested changes might break existing sites which already have workarounds in place for this kind of problems, thus I tend to reject this patch.

This is a lot of configuration options for such an edge case. I might include something like that but only if other users require it as well. For now I will postpone the patch.

If you still want to go down this path, then I recommend to alter away the hooks from a custom module. Like this you do not have to maintain a patched version of authcache in your project. The following example should give you some pointers on how to do that (this assumes a custom module called mymodule). Disclaimer: code written from the top of my head, not tested at all.

/**
 * Implements hook_module_implements_alter().
 */
function mymodule_module_implements_alter(&$implementations, $hook) {
  $hooks = [
    // Disable hiding of number-of-new-comments-link on node teasers.
    'node_view_alter', 
    // Disable replacing the edit-link on comments.
    'comment_view_alter',
    // Disable replacing the username in the comment form.
    'form_comment_form_alter',
  ];
  if (in_array($hook, $hooks, TRUE)) {
    unset($implementations['authcache_comment']);
  }
}

/**
 * Implements hook_theme_registry_alter().
 */
function mymodule_theme_registry_alter(&$registry) {
  // Disable replacing the "new" marker with empty span.
  if (isset($registry['comment']['preprocess functions']))  {
    $registry['comment']['preprocess functions'] = array_filter($registry['comment']['preprocess functions'], function ($item) {
      return $item !== 'authcache_comment_preprocess_comment';
    });
  }
}

Edit: Docs on hook_theme_registry_alter and hook_module_implements_alter.