Disable memcache on local or dev environments (Drupal 8)

Even when I place all of the memcache settings inside an if statement in settings.php, this doesn't work:

// Example config for settings.php
/**
 * Configure memcache.
 *
 * We place memcache configuration behind a feature flag based on existence of
 * the Memcache (or Memcached) Pecl extensions. You can explicitly disable
 */
$memcache_exists = class_exists('Memcache', FALSE);
$memcached_exists = class_exists('Memcached', FALSE);
if ($memcache_exists || $memcached_exists) {

  // This is a default single-machine memcache configuration on localhost.
  $settings['memcache']['servers'] = [
    '127.0.0.1:11211' => 'default',
  ];
  $settings['memcache']['bins'] = [
    'default' => 'default',
  ];

  // Our memcache server is not shared by multiple Drupal apps, so we do not
  // need to add prefixes to the memcache bin names.
  $settings['memcache']['key_prefix'] = '';

  // Enable stampede protection.
  $settings['memcache']['stampede_protection'] = TRUE;

  // Enable compression for PHP 7.
  $settings['memcache']['options'][Memcached::OPT_COMPRESSION] = TRUE;

  // Move locks to memcache.
  $settings['container_yamls'][] = $app_root . '/' . $site_path .'/memcache.yml';

  // Use memcache for specific cache tables.
  $settings['cache']['bins']['bootstrap'] = 'cache.backend.memcache';
  $settings['cache']['bins']['config'] = 'cache.backend.memcache';
  $settings['cache']['bins']['data'] = 'cache.backend.memcache';
  $settings['cache']['bins']['default'] = 'cache.backend.memcache';
  $settings['cache']['bins']['discovery'] = 'cache.backend.memcache';
  $settings['cache']['bins']['dynamic_page_cache'] = 'cache.backend.memcache';
  $settings['cache']['bins']['entity'] = 'cache.backend.memcache';
  $settings['cache']['bins']['menu'] = 'cache.backend.memcache';
  $settings['cache']['bins']['page'] = 'cache.backend.memcache';
  $settings['cache']['bins']['render'] = 'cache.backend.memcache';
  $settings['cache']['bins']['toolbar'] = 'cache.backend.memcache';

  // Use memcache as the default caching mechanism.
  $settings['cache']['default'] = 'cache.backend.memcache';

}

Am I missing something?

A colleague, @marthinal, has determined that memcache module doesn't need to be enabled in the site (ie, in core.extensions.yml) so this may actually be one way to solve this problem, although not ideal.

Indeed Acquia has a statement that says the memcache module does not need to be enabled for the configuration to work:

If your website uses either automated testing or the memcache_admin submodule, you must enable the Memcache API and Integration module. Although Drupal 8 doesn’t require you to enable the module, Acquia recommends enabling the module to receive notifications about module updates.

I will test locally and report back.

I've narrowed down the problem to being caused by show_memcache_statistics being set to 1 in memcache_admin.settings.yml

If I set show_memcache_statistics to 0 in settings.local.php and ensure $settings['memcache'] is not set by wrapping it in an if statement like the one in comment #2, the problems go away.

So, currently, to disable memcache definitively in local environments, without having to manually go and disable the modules in Drupal, add the following lines to your settings.local.php:

$settings['memcache'] = [];
$config['memcache_admin.settings']['show_memcache_statistics'] = '0';

This is unfortunate and confusing and so maybe there is something that could be done in memcache_admin module to respect presence or absence of $settings['memcache'] before trying to load?