Display warning if non existent parameters are passed in --checks and --categories

[ernilambar]

Proper warning message should be displayed rather than fatal error when non existent check is passed to --checks

wp plugin check hello-universe --checks=nonexistent_check

Currently it generates PHP fatal error.

Fatal error: Uncaught Exception: Check with the slug "nonexistent_check" does not exist. in /var/www/html/wp-content/plugins/plugin-check/includes/Checker/Default_Check_Collection.php:158

May be we should display warning message like

WARNING: Invalid check slug 'nonexistent_check'

We could implement similar for categories also.

wp plugin check hello-universe --categories=nonexistent_category

[ernilambar]

This issue is similar to #360 . Would it be of worth implementing the validation here for --checks and --categories? Not a critical issue though.

cc: @swissspidy @felixarntz @mukeshpanchal27

[swissspidy]

I suppose we can catch any exceptions and turn them into proper error messages (not warnings)

[ernilambar]

I suppose we can catch any exceptions and turn them into proper error messages (not warnings)

@swissspidy Please check #383

[swissspidy]

I was thinking more like something like this in the command class:

try {
....
} catch ( Exception $error ) {
	WP_CLI::error( $error->getMessage() );
}

We already do this in some places

[ernilambar]

This fatal error comes before execution reaches to CLI command class. Even when public function check( $args, $assoc_args ) in Plugin_Check_Command function is empty, this error appears.
It is triggered from Plugin_Request_Utility::initialize_runner().