Can't access specific admin pages I have a Drupal 8 site set up in Docksal. It was version 8.6.15, and needed updates to core and several modules. Bear with me - I don't have complete notes, because I thought everything had worked. I'm more than happy to debug... I just don't know where/how/what to look for in this case.

I would just roll back to a backed up version of the site. But that is missing ( My own fault)

The first problem I encountered, was not being able to update with Drush anymore. So I used composer to to attempt updating, with "composer require drupal/core --update-with-all-dependencies" - this was my first time doing so. 

It didn't work. I had to update composer in order to continue on. After using "composer prohibits Drupal/core:8.7.3," I got several results, so I went ahead and updated them. I would tell you all I uploaded, but that was yesterday and I did not save those notes. Sorry. I also did an update of composer itself, all the packages. that appeared out of date. There were a couple that would not update, rejected by constraints.

Updated composer, and Drupal is now 8.7.3. I also did a bunch of module updates on the site as well. 

I have an issue where the admin area shows I'm still on Drupal 8.6.15, even though Composer shows the latest version. I assumed this was a separate issue, but maybe it's related. There is an issue with this site being set up with drupal/drupal and not drupal/core. Something to do with the composer json.

Everything seemed fine, but when I tried to navigate to some of the admin pages (Content, Configuration or People page), I get an error:


  Fatal error: require(): Failed opening required '/var/www/docroot/vendor/composer/../doctrine/common/lib/Doctrine/Common/Reflection/ClassFinderInterface.php'
  (include_path='.:/usr/local/lib/php') in
  /var/www/docroot/vendor/symfony/class-loader/ApcClassLoader.php on
  line 112


Not even sure what first steps might be on this. When I type composer outdated, I don't see anything called class-loader or classfinder

Looking at ApcClassLoader.php, I see 'require $file;' on line 112: 

 public function loadClass($class)
    {
        if ($file = $this-&gt;findFile($class)) {
            require $file;

            return true;
        }
    }
Not sure whether or not this will actually fix your issue, but I'd try:


update the drupal/core version to in composer.json to be ^8.7.0
if you're using webflo/drupal-core-require-dev, update that to ^8.7.0 as per https://www.drupal.org/docs/8/update/update-core-via-composer
run composer update drupal/core webflo/drupal-core-require-dev --with-dependencies
run your database updates, drush updb or site.com/update.php


If that still doesn't work, try:


deleting your vendor directory, core directory, and composer.lock
run composer install