Hanami has a convenient way to load commands from third party gems, so if you want to add a Hanami compatible gem, you only have to add it inside your project’s Gemfile in the :plugins group.

# Gemfile
group :plugins do
  gem "hanami-reloader"
end

Add a command

Imagine you want to build a fictional gem called hanami-webpack with a CLI command: hanami webpack setup.

# lib/hanami/webpack.rb
module Hanami
  module Webpack
    module CLI
      class Setup < Hanami::CLI::Command
        def call(*)
          # setup code goes here...
        end
      end
    end
  end
end
Hanami::CLI.register "webpack setup", Hanami::Webpack::CLI::Setup

This code above will make the following command available:

$ bundle exec hanami webpack setup

Hook into existing command

Third-party Hanami plugins can hook into existing commands, in order to enhance the default behavior. During the command execution lifecycle you can execute custom code before and/or after the command itself.

Let’s say we want to build a fictional gem hanami-database-analyzer, that prints database stats after db migrate is ran.

# lib/hanami/database/analizer.rb
module Hanami
  module Database
    module Analyzer
      class Stats
        def call(*)
          puts "The database has 23 tables"
        end
      end
    end
  end
end
Hanami::CLI::Commands.before("db migrate") { puts "I am about to migrate database.." }
Hanami::CLI::Commands.after "db migrate", Hanami::Database::Analyzer::Stats.new

By running db migrate, the third-party code is executed:

$ bundle exec hanami db migrate
I am about to migrate database..
# ...
The database has 23 tables