Allow the :hosts and :roles keys to accept lambdas, which will be evaluated lazily to allow runtime selection of hosts and roles in tasks

git-svn-id: http://svn.rubyonrails.org/rails/tools/capistrano@7043 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Allow the :hosts and :roles keys to accept lambdas, which will be evaluated lazily to allow runtime selection of hosts and roles in tasks [Jamis Buck]
+
 * Use `which' to test whether a command exists in the remote path, instead of `test -p' [Jamis Buck]
 
 * Make sure the connection factory is established synchronously, to avoid multiple gateway instances being spawned [Jamis Buck]

lib/capistrano/configuration.rb

@@ -25,6 +25,9 @@ module Capistrano
       @logger = Logger.new
     end
 
+    # make the DSL easier to read when using lazy evaluation via lambdas
+    alias lazy lambda
+
     # The includes must come at the bottom, since they may redefine methods
     # defined in the base class.
     include Connections, Execution, Loading, Namespaces, Roles, Servers, Variables

lib/capistrano/configuration/servers.rb

@@ -53,17 +53,23 @@ module Capistrano
 
       def server_list_from(hosts)
         hosts = hosts.split(/,/) if String === hosts
-        Array(hosts).map { |s| String === s ? ServerDefinition.new(s.strip) : s }
+        hosts = build_list(hosts)
+        hosts.map { |s| String === s ? ServerDefinition.new(s.strip) : s }
       end
 
       def role_list_from(roles)
         roles = roles.split(/,/) if String === roles
-        Array(roles).map do |role|
+        roles = build_list(roles)
+        roles.map do |role|
           role = String === role ? role.strip.to_sym : role
           raise ArgumentError, "unknown role `#{role}'" unless self.roles.key?(role)
           role
         end
       end
+
+      def build_list(list)
+        Array(list).map { |item| item.respond_to?(:call) ? item.call : item }.flatten
+      end
     end
   end
 end

test/configuration/servers_test.rb

@@ -77,4 +77,14 @@ class ConfigurationServersTest < Test::Unit::TestCase
     task = new_task(:testing, @config, :roles => :web)
     assert_equal %w(app1 app2 app3).sort, @config.find_servers_for_task(task, :roles => :app).map { |s| s.host }.sort
   end
+
+  def test_find_servers_with_lambda_for_hosts_should_be_evaluated
+    assert_equal %w(foo), @config.find_servers(:hosts => lambda { "foo" }).map { |s| s.host }.sort
+    assert_equal %w(bar foo), @config.find_servers(:hosts => lambda { %w(foo bar) }).map { |s| s.host }.sort
+  end
+
+  def test_find_servers_with_lambda_for_roles_should_be_evaluated
+    assert_equal %w(app1 app2 app3), @config.find_servers(:roles => lambda { :app }).map { |s| s.host }.sort
+    assert_equal %w(app2 file), @config.find_servers(:roles => lambda { [:report, :file] }).map { |s| s.host }.sort
+  end
 end