Dynamic roles (closes #11107, thanks for the awesome patch!)

git-svn-id: http://svn.rubyonrails.org/rails/tools/capistrano@8905 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Dynamic roles (e.g. role(:app) { "host.name" }) [dmasover]
+
 * Implement Bzr#next_revision so that pending changes can be reported correctly [casret]
 
 * Use a proper export command for bzr SCM [drudru]

lib/capistrano/configuration/roles.rb

@@ -1,4 +1,5 @@
 require 'capistrano/server_definition'
+require 'capistrano/role'
 
 module Capistrano
   class Configuration
@@ -15,7 +16,7 @@ module Capistrano
 
       def initialize_with_roles(*args) #:nodoc:
         initialize_without_roles(*args)
-        @roles = Hash.new { |h,k| h[k] = [] }
+        @roles = Hash.new { |h,k| h[k] = Role.new }
       end
 
       # Define a new role and its associated servers. You must specify at least
@@ -41,9 +42,10 @@ module Capistrano
       # that call to "role":
       #
       #   role :web, "web2", "web3", :user => "www", :port => 2345
-      def role(which, *args)
+      def role(which, *args, &block)
         options = args.last.is_a?(Hash) ? args.pop : {}
         which = which.to_sym
+        roles[which].push(block, options) if block_given?
         args.each { |host| roles[which] << ServerDefinition.new(host, options) }
       end
     end

lib/capistrano/role.rb

@@ -0,0 +1,112 @@
+
+module Capistrano
+  class Role
+    include Enumerable
+
+    def initialize(*list)
+      @static_servers = []
+      @dynamic_servers = []
+      push(*list)
+    end
+
+    def each(&block)
+      servers.each &block
+    end
+
+    def push(*list)
+      options = list.last.is_a?(Hash) ? list.pop : {}
+      list.each do |item|
+        if item.respond_to?(:call)
+          @dynamic_servers << DynamicServerList.new(item, options)
+        else
+          @static_servers << self.class.wrap_server(item, options)
+        end
+      end
+    end
+    alias_method :<<, :push
+
+    def servers
+      @static_servers + dynamic_servers
+    end
+    alias_method :to_ary, :servers
+
+    def empty?
+      servers.empty?
+    end
+
+    # Resets the cache, so that proc values may be recalculated.
+    # There should be a command in Configuration::Roles to do this,
+    # but I haven't needed it yet, and I'm not sure yet
+    # what to call that command. Suggestions?
+    def reset!
+      @dynamic_servers.each { |item| item.reset! }
+    end
+
+    # Clears everything. I still thing this should be 'clear!', but that's not
+    # the way Array does it.
+    def clear
+      @dynamic_servers.clear
+      @static_servers.clear
+    end
+
+    # Mostly for documentation purposes. Doesn't seem to do anything.
+    protected
+
+    # This is the combination of a block, a hash of options, and a cached value.
+    # It is protected because it is an implementation detail -- the original
+    # implementation was two lists (blocks and cached results of calling them).
+    class DynamicServerList
+      def initialize (block, options)
+        @block = block
+        @options = options
+        @cached = []
+        @is_cached = false
+      end
+
+      # Convert to a list of ServerDefinitions
+      def to_ary
+        unless @is_cached
+          @cached = Role::wrap_list(@block.call(@options), @options)
+          @is_cached = true
+        end
+        @cached
+      end
+
+      # Clear the cached value
+      def reset!
+        @cached.clear
+        @is_cached = false
+      end
+    end
+
+    # Attribute reader for the cached results of executing the blocks in turn
+    def dynamic_servers
+      @dynamic_servers.inject([]) { |list, item| list.concat item }
+    end
+
+    # Wraps a string in a ServerDefinition, if it isn't already.
+    # This and wrap_list should probably go in ServerDefinition in some form.
+    def self.wrap_server (item, options)
+      item.is_a?(ServerDefinition) ? item : ServerDefinition.new(item, options)
+    end
+
+    # Turns a list, or something resembling a list, into a properly-formatted
+    # ServerDefinition list. Keep an eye on this one -- it's entirely too
+    # magical for its own good. In particular, if ServerDefinition ever inherits
+    # from Array, this will break.
+    def self.wrap_list (*list)
+      options = list.last.is_a?(Hash) ? list.pop : {}
+      if list.length == 1
+        if list.first.nil?
+          return []
+        elsif list.first.is_a?(Array)
+          list = list.first
+        end
+      end
+      options.merge! list.pop if list.last.is_a?(Hash)
+      list.map do |item|
+        self.wrap_server item, options
+      end
+    end
+  end
+end

test/configuration/roles_test.rb

@@ -1,5 +1,6 @@
 require "#{File.dirname(__FILE__)}/../utils"
 require 'capistrano/configuration/roles'
+require 'capistrano/server_definition'
 
 class ConfigurationRolesTest < Test::Unit::TestCase
   class MockConfig
@@ -16,6 +17,10 @@ class ConfigurationRolesTest < Test::Unit::TestCase
     @config = MockConfig.new
   end
 
+  def assert_role_equals(list)
+    assert_equal list, @config.roles[:app].map { |s| s.host }
+  end
+
   def test_initialize_should_initialize_roles_collection
     assert @config.original_initialize_called
     assert @config.roles.empty?
@@ -29,13 +34,34 @@ class ConfigurationRolesTest < Test::Unit::TestCase
   def test_role_with_one_argument_should_add_to_roles_collection
     @config.role :app, "app1.capistrano.test"
     assert_equal [:app], @config.roles.keys
-    assert_equal %w(app1.capistrano.test), @config.roles[:app].map { |s| s.host }
+    assert_role_equals %w(app1.capistrano.test)
+  end
+
+  def test_role_block_returning_single_string_is_added_to_roles_collection
+    @config.role :app do
+      'app1.capistrano.test'
+    end
+    assert_role_equals %w(app1.capistrano.test)
   end
 
   def test_role_with_multiple_arguments_should_add_each_to_roles_collection
     @config.role :app, "app1.capistrano.test", "app2.capistrano.test"
     assert_equal [:app], @config.roles.keys
-    assert_equal %w(app1.capistrano.test app2.capistrano.test), @config.roles[:app].map { |s| s.host }
+    assert_role_equals %w(app1.capistrano.test app2.capistrano.test)
+  end
+
+  def test_role_with_block_and_strings_should_add_both_to_roles_collection
+    @config.role :app, 'app1.capistrano.test' do
+      'app2.capistrano.test'
+    end
+    assert_role_equals %w(app1.capistrano.test app2.capistrano.test)
+  end
+
+  def test_role_block_returning_array_should_add_each_to_roles_collection
+    @config.role :app do
+      ['app1.capistrano.test', 'app2.capistrano.test']
+    end
+    assert_role_equals %w(app1.capistrano.test app2.capistrano.test)
   end
 
   def test_role_with_options_should_apply_options_to_each_argument
@@ -44,4 +70,66 @@ class ConfigurationRolesTest < Test::Unit::TestCase
       assert_equal({:extra => :value}, server.options)
     end
   end
-end
+
+  def test_role_with_options_should_apply_options_to_block_results
+    @config.role :app, :extra => :value do
+      ['app1.capistrano.test', 'app2.capistrano.test']
+    end
+    @config.roles[:app].each do |server|
+      assert_equal({:extra => :value}, server.options)
+    end
+  end
+
+  def test_options_should_apply_only_to_this_argument_set
+    @config.role :app, 'app1.capistrano.test', 'app2.capistrano.test' do
+      ['app3.capistrano.test', 'app4.capistrano.test']
+    end
+    @config.role :app, 'app5.capistrano.test', 'app6.capistrano.test', :extra => :value do
+      ['app7.capistrano.test', 'app8.capistrano.test']
+    end
+    @config.role :app, 'app9.capistrano.test'
+
+    option_hosts = ['app5.capistrano.test', 'app6.capistrano.test', 'app7.capistrano.test', 'app8.capistrano.test']
+    @config.roles[:app].each do |server|
+      if (option_hosts.include? server.host)
+        assert_equal({:extra => :value}, server.options)
+      else
+        assert_not_equal({:extra => :value}, server.options)
+      end
+    end
+  end
+
+  # Here, the source should be more readable than the method name
+  def test_role_block_returns_options_hash_is_merged_with_role_options_argument
+    @config.role :app, :first => :one, :second => :two do
+      ['app1.capistrano.test', 'app2.capistrano.test', {:second => :please, :third => :three}]
+    end
+    @config.roles[:app].each do |server|
+      assert_equal({:first => :one, :second => :please, :third => :three}, server.options)
+    end
+  end
+
+  def test_role_block_can_override_role_options_argument
+    @config.role :app, :value => :wrong do
+      Capistrano::ServerDefinition.new('app.capistrano.test')
+    end
+    @config.roles[:app].servers
+    @config.roles[:app].servers.each do |server|
+      assert_not_equal({:value => :wrong}, server.options)
+    end
+  end
+
+  def test_role_block_can_return_nil
+    @config.role :app do
+      nil
+    end
+    assert_role_equals ([])
+  end
+
+  def test_role_block_can_return_empty_array
+    @config.role :app do
+      []
+    end
+    assert_role_equals ([])
+  end
+end