Error: 'mem' is not a registered wp command.

[einkoro]

It looks like the mem WP CLI command is not being detected when installing the develop branch via composer:

$ composer require tollmanz/wordpress-pecl-memcached-object-cache:~2.0
./composer.json has been updated
Loading composer repositories with package information
Updating dependencies (including require-dev)                                                           
  - Installing tollmanz/wordpress-pecl-memcached-object-cache (dev-develop 8a6f581)
    Cloning 8a6f581dfb28c4802bce76a66012bab5a81c2a0f

Writing lock file
Generating autoload files

$ vendor/wp-cli/wp-cli/bin/wp mem install
Error: 'mem' is not a registered wp command. See 'wp help'.

Taking a closer look it seems to be because the plugin itself is within the src directory after the installation so the plugin isn't loaded by WordPress:

$ ls -lha www/wp-content/plugins/wordpress-pecl-memcached-object-cache
total 32
drwxr-xr-x+  8 jpingel  staff   272B  8 Jun 20:15 .
drwxr-xr-x@ 39 jpingel  staff   1.3K  8 Jun 20:39 ..
drwxr-xr-x+ 14 jpingel  staff   476B  8 Jun 20:15 .git
-rw-r--r--+  1 jpingel  staff   552B  8 Jun 20:15 .travis.yml
-rw-r--r--+  1 jpingel  staff   749B  8 Jun 20:15 composer.json
-rw-r--r--+  1 jpingel  staff   7.6K  8 Jun 20:15 readme.md
drwxr-xr-x+  7 jpingel  staff   238B  8 Jun 20:15 src
drwxr-xr-x+  7 jpingel  staff   238B  8 Jun 20:15 tests

Shuffling everything in src up into the root of the repository would fix this.