Fatal error: Call to a member function url() on null

The problem seems to be related to "orphaned" comments, where the Comment entity still exists, but references an Entity that has been deleted.
In these cases, the call to $comment->getCommentedEntity() in rdf_comment_storage_load() returns null.

Here's a patch I created as a work-around for this issue, as it was causing issues with things like XML Sitemap.

This just places a guard to make sure that the entity is valid before attempting to get the URL.

I can confirm that patch provided at #4 solved the issue for me. The issue occurred when I migrated comments from d7 website to d8.

But my case for reproduction is different. I created a view that counts comment number for the specific user and when the view is shown, the website returns error 500, but the cause for the error is the same.

I saw this when running drush migrate-rollback --all on drupal 8.4; the patch in #4 improves the situation but, at least here, it also happened that in some other case it's the parent comment entity to be null.

The check on $comment->hasParentComment() does not seem enough because even when this passes $comment->getParentComment() could still return null.

I don't know the low level details, I am just reporting my observations.

I see similar issues reported in #2793437: Fatal error: Call to a member function url() on a non-object in line number 243 rdf.module, #2558923: Comment migrations produce fatal errors when RDF module is enabled and #2863744: Comment Admin & Deleting Users with comments fails with error..

I don't have git and the related stuff installed now, so no patch, sorry, but the very simple and very obvious solution is to add this, too:

    if ($comment->hasParentComment()) {
      $parent = $comment->getParentComment();
      if ($parent) {
        $comment->rdf_data['pid_uri'] = $parent->url();
      }
    }

Just posting patch based on #4 and #11.

..reposting

paranojik,

I just wanted to confirm that patch #15 for the RDF module did work for me, but I also had to install patch #15 to the views/Plugin/field/BulkForm.php file found here: https://www.drupal.org/project/drupal/issues/2951493.

At first glance, it appears I had originally had stranded revision data.

Thank you for the patch! I'm fairly new to Drupal, but am hoping to help take care of some various issues as well and am able to provide patches every now and again if someone isn't setup to do so. Will keep a lookout in the forums. :)

Just FYI, I will likely post a comment in the other issue forum so people know it may be necessary to install both patches in their case until these updates are rolled into the core.

I believe the root problem is incorrect getCommentedEntity() @return value doc; I've raised #3001851: Incorrect documented CommentInterface::getCommentedEntity() return value for this.

The following condition in #15 is incorrect:

if (!$entity instanceof \Drupal\Core\Entity\Entity) {
...
}

The toUrl() method is provided by the \Drupal\Core\Entity\EntityInterface, not by \Drupal\Core\Entity\Entity.

Also, there's no more need to check $comment->hasParentComment() since the $parent value is checked in next line. Should be something like this:

    $comment->rdf_data['entity_uri'] = $entity->toUrl()->toString(TRUE)->getGeneratedUrl();
    if ($parent = $comment->getParentComment()) {
      $comment->rdf_data['pid_uri'] = $parent->toUrl();
    }

Also, the return statement breaks processing multiple entities.

Here we go. Fixed issues I found in #15.

Interdiff included.

...
+      if ($parent = $comment->getParentComment()) {
+        $comment->rdf_data['pid_uri'] = $parent->toUrl();
+      }

While not strictly forbidden by the coding standard, I'd avoid assignments in conditions.
In this case splitting the assignment would also follow the predominant style used in the rest of the file.

Ciao,
Antonio

I don't think the assignment in condition is such a big deal. I've looked through the code and found 20 such assignments just in the comment module so it's a common practice.

I'm more worried by the test failure.

#15 worked for me. Thanks a lot.

#21 nor #15 appear to work with 8.7.alpha2

Added a patch according latest updates.
I've not added an interdiff file while I wasn't able to make to apply any of old patches.

Couldn't apply the latest patch into 8.7. Adding a new patch according to latest updates in 8.7.x release.

Adding a new patch according to latest updates in 8.7.x release.

Failed to apply #29 into Drupal 8.7.5 release.
Adding a new patch according to updates in 8.7.5 release.

it also needs a way to clean-up "orphans" probably in follow-up issue

PS: in D7 we detected orphan actions, maybe makes sense for comment as well in d8

This issue can still sometimes happen even with comments posted on D8 page, not on the comments migrated from D7 pages.

This bug essentially causes the websites with orphaned comments to not load.

Also experiencing it failing on migrate:rollaback
Call to a member function toUrl() on null in rdf_comment_storage_load() (line 245

Confirm that If I uninstall RDF rollback works as expected.

Added #2793437: Fatal error: Call to a member function url() on a non-object in line number 243 rdf.module as a duplicate and will close that, so also added and aviral2809, Ruedische, jeetmail72, KlemenDEV, hchonov from that issue for credit.

Just a note. #4 was the only thing that worked for me on 8.8.*

Found another duplicate in #2863744: Comment Admin & Deleting Users with comments fails with error. so closed that, adding as related and adding contributors.

Added rerolled patch for 8.9.x & 9.1.x, Kindly review.

Following the steps in the IS I was unable to reproduce the error.

Reading the issue the majority of comments refer to getting this error after a migration of comments but KlemenDEV reports this can happen with comments posted on a D8 site, see #36.

I think this is a duplicate of #2614720: Fatal errors while loading/building orphaned comments. That issue includes a test and changes to the comment module to handle orphans as well as the changes to rdf.module that are included.

@pameeela, thanks, seeing this in the BugSmash queu got me to take another look!

Thanks for reporting this issue. We rely on issue reports like this one to resolve bugs and improve Drupal core.

I'm closing this as a duplicate of #2614720: Fatal errors while loading/building orphaned comments and will move credit to that issue.

If anyone can provide information on why this issue is different, please add complete steps to reproduce the issue (starting from "Install Drupal core"), document those steps in the issue summary and set the issue status back to "Active".