More natural api when you are just applying accessory to a single tag

Author: David Heinemeier Hansson

lib/kamal/configuration/accessory.rb

@@ -207,7 +207,9 @@ def hosts_from_roles
  end
 
  def hosts_from_tags
- if accessory_config.key?("tags")
+ if accessory_config.key?("tag")
+ extract_hosts_from_config_with_tag(accessory_config["tag"])
+ elsif accessory_config.key?("tags")
  accessory_config["tags"].flat_map { |tag| extract_hosts_from_config_with_tag(tag) }
  end
  end

lib/kamal/configuration/docs/accessory.yml

@@ -53,8 +53,10 @@ accessories:
  - mysql-db2
  roles:
  - mysql
+ tag: writer
  tags:
  - writer
+ - reader
 
  # Custom command
  #

lib/kamal/configuration/validator/accessory.rb

@@ -2,8 +2,8 @@ class Kamal::Configuration::Validator::Accessory < Kamal::Configuration::Validat
  def validate!
  super
 
- if (config.keys & [ "host", "hosts", "roles", "tags" ]).size != 1
- error "specify one of `host`, `hosts`, `roles` or `tags`"
+ if (config.keys & [ "host", "hosts", "roles", "tag", "tags" ]).size != 1
+ error "specify one of `host`, `hosts`, `roles`, `tag` or `tags`"
  end
 
  validate_docker_options!(config["options"])

test/configuration/accessory_test.rb

@@ -73,7 +73,11 @@ class ConfigurationAccessoryTest < ActiveSupport::TestCase
  },
  "proxy" => {
  "image" => "proxy:latest",
- "tags" => [ "writer" ]
+ "tags" => [ "writer", "reader" ]
+ },
+ "logger" => {
+ "image" => "logger:latest",
+ "tag" => "writer"
  }
  }
  }
@@ -111,7 +115,7 @@ class ConfigurationAccessoryTest < ActiveSupport::TestCase
  assert_equal [ "1.1.1.5" ], @config.accessory(:mysql).hosts
  assert_equal [ "1.1.1.6", "1.1.1.7" ], @config.accessory(:redis).hosts
  assert_equal [ "1.1.1.1", "1.1.1.2" ], @config.accessory(:monitoring).hosts
- assert_equal [ "1.1.1.1", "1.1.1.3" ], @config.accessory(:proxy).hosts
+ assert_equal [ "1.1.1.1", "1.1.1.3", "1.1.1.2" ], @config.accessory(:proxy).hosts
  end
 
  test "missing host" do
@@ -129,7 +133,7 @@ class ConfigurationAccessoryTest < ActiveSupport::TestCase
  exception = assert_raises(Kamal::ConfigurationError) do
  Kamal::Configuration.new(@deploy)
  end
- assert_equal "accessories/mysql: specify one of `host`, `hosts`, `roles` or `tags`", exception.message
+ assert_equal "accessories/mysql: specify one of `host`, `hosts`, `roles`, `tag` or `tags`", exception.message
  end
 
  test "all hosts" do