This is an updated Rakefile to for those who want to use Sequel with Hanami-RB, using the nifty Rails-like commands.

Rakefile

#
# You might need dotenv and colorize gems for this one to play nice
# 
# The original work by Rodrigo Panachi:
# http://rpanachi.com/2016/04/11/from-rails-to-hanami-part2-sequel-migrations-model-validations-specs-fixtures
# 
# For some reason I couldn't get his solution to work for the life of me, so
# I include the Hanami environment and used slightly more concise forms of `exec`
# as well as Sequel DB directly here and there. hanami/rake_tasks seems to be loading something which
# breaks migrations, so I advise you to keep that one commented out. Doesn't affect minitest.
#

require 'rake'
# require 'hanami/rake_tasks' # Uncomment this line if you don't want to use this rakefile
require 'rake/testtask'

Rake::TestTask.new do |t|
  t.pattern = 'spec/**/*_spec.rb'
  t.libs    << 'spec'
  t.warning = false
end

task default: :test
task spec: :test


# require_relative 'config/environment'
require 'colorize'
require 'dotenv'
ENV['DATABASE_URL'] = Dotenv.load('.env.development')['DATABASE_URL']
APP_NAME = Dotenv.load('.hanamirc')['project']
require_relative 'lib/config/sequel.rb' # This is where sequel is setup and defined

throw "ENV['DATABASE_URL'] is missing. Can't work with Sequel or PostgreSQL. \nCheck .env.development or .env.test" unless ENV['DATABASE_URL']

namespace :db do
  require 'sequel'
  Sequel.extension(:migration)
  MIGRATIONS_PATH = 'db/migrations'

  # Show available schema versions
  def database_versions
    DB[:schema_migrations].order(:filename).select_map(:filename) || []
  end

  # Split postgres URI into pieces
  def split_database_url(url)
    user, pass, host, database = url.scan(/postgres:\/\/(.+?):(.+?)@(.+?)\/(.+?)$/).first
    data = {
      user:     user,
      pass:     pass,
      host:     host,
      database: database
    }
  end

  # Connection URL without the DB
  def database_connection_url
    db = split_database_url ENV['DATABASE_URL']
    db_conn = "postgres://#{db[:user]}:#{db[:pass]}@#{db[:host]}"
  end

  # Sorted list of migrations
  def db_migrations
    Dir[MIGRATIONS_PATH + "/*.rb"].map { |f| File.basename(f) }.sort
  end

  # Run DB Migrator
  def db_migrate(version = db_migrations.last)
    Sequel::Migrator.run(DB, MIGRATIONS_PATH, target: version.to_i)
  end

  # # Check if the version has been migrated
  # def db_migrated?(version)
  #   db_versions.include?(version.to_s)
  # end

  desc 'Seed the database with pre-defined data from db/seeds.rb'
  task :seed do

    load 'db/seeds.rb'
  end

  desc 'Print current schema/migration version.'
  task :version do
    puts "\t\nCurrent Schema Version: " + "#{database_versions.last}\n".yellow
  end

  desc "Perform migration up to latest migration available."
  task :migrate do |t, args|
    db_migrate(args[:version] || db_migrations.last)
    Rake::Task['db:version'].execute
  end

  desc "Perform migration reset (full rollback and migration). Doesn't work in production."
  task :reset do
    if (ENV["HANAMI_ENV"] || ENV["RACK_ENV"]) == "production"
      abort "You can't run this rake on production environment"
    end

    db_migrate(0)
    db_migrate(db_migrations.last)
    Rake::Task['db:version'].execute
  end

  desc "Perform rollback to specified target or previous version as default"
  task :rollback, [:version] do |t, args|
    version = args[:version] || database_versions[-2]
    db_migrate(version)
    Rake::Task['db:version'].execute
  end

  desc "Creates a database specified in the ENV['DATABASE_URL']"
  task :create do
    db = split_database_url ENV['DATABASE_URL']
    puts "\t\nAttempting to create #{db[:database]}... ".green
    result = system("PGPASSWORD=#{db[:pass]} createdb -w -h localhost -p 5432 -U #{db[:user]} #{db[:database]}")
    if result
      print "success!\n".bold.green
    else
      puts
      puts result
    end
  end

  desc "Drops database if it exists. Doesn't work in production."
  task :drop do
    if (ENV["HANAMI_ENV"] || ENV["RACK_ENV"]) == "production"
      abort "You can't run this rake on production environment"
    end
    db = split_database_url ENV['DATABASE_URL']
    puts "\n\tWARNING! Dropping ".red + "#{db[:database]}\n".red.bold
    result = exec("PGPASSWORD=#{db[:pass]} dropdb -w -h localhost -p 5432 -U #{db[:user]} #{db[:database]}")
    puts result
  end

  desc "Start a PostgreSQL console environment."
  task :console do
    exec "psql #{ENV['DATABASE_URL']}"
  end

end