RUBY-945 Add #database_names method to client

Author: estolfo

lib/mongo/client.rb

@@ -223,6 +223,20 @@ def write_concern
       @write_concern ||= WriteConcern.get(options[:write])
     end
 
+    # Get the names of all databases.
+    #
+    # @example Get the database names.
+    #   client.database_names
+    #
+    # @return [ Array<String> ] The names of the databases.
+    #
+    # @since 2.0.5
+    def database_names
+      Database.new(self, Database::ADMIN, options).command(
+        listDatabases: 1
+      ).first['databases'].collect { |info| info['name'] }
+    end
+
     private
 
     def create_from_addresses(addresses, opts = {})

spec/mongo/client_spec.rb

@@ -569,4 +569,11 @@
       end
     end
   end
+
+  describe '#database_names' do
+
+    it 'returns a list of database names' do
+      expect(root_authorized_client.database_names).to include('admin', 'local')
+    end
+  end
 end

spec/support/authorization.rb

@@ -77,7 +77,8 @@
     Mongo::Auth::Roles::USER_ADMIN_ANY_DATABASE,
     Mongo::Auth::Roles::DATABASE_ADMIN_ANY_DATABASE,
     Mongo::Auth::Roles::READ_WRITE_ANY_DATABASE,
-    Mongo::Auth::Roles::HOST_MANAGER
+    Mongo::Auth::Roles::HOST_MANAGER,
+    Mongo::Auth::Roles::CLUSTER_ADMIN
   ]
 )
 
@@ -105,8 +106,8 @@
 # @since 2.0.
 TEST_READ_WRITE_USER = Mongo::Auth::User.new(
   database: TEST_DB,
-  user: 'test-user',
-  password: 'password',
+  user: TEST_USER.name,
+  password: TEST_USER.password,
   roles: [ Mongo::Auth::Roles::READ_WRITE, Mongo::Auth::Roles::DATABASE_ADMIN ]
 )