Fix parallel command execution logging parallely - GH434

Also add unit tests that reproduce the problem

Gemfile

@@ -9,4 +9,5 @@ gemspec
 #
 group :development do
   gem "rake"
+  gem "pry"
 end

lib/capistrano/configuration/actions/invocation.rb

@@ -163,10 +163,11 @@ module Capistrano
 
           if tree.branches.any? || tree.fallback
             _, servers = filter_servers(options)
-            branches = servers.map{|server| tree.branches_for(server)}.compact
+            branches = branches_for_servers(tree,servers)
             case branches.size
             when 0
               branches = tree.branches.dup + [tree.fallback]
+              branches.compact!
               case branches.size
               when 1
                 logger.debug "no servers for #{branches.first}"
@@ -178,13 +179,7 @@ module Capistrano
               logger.debug "executing #{branches.first}" unless options[:silent]
             else
               logger.debug "executing multiple commands in parallel"
-              branches.each {|maybe_branch|
-                if(maybe_branch.is_a?(Array))
-                  maybe_branch.each {|branch| logger.trace "-> #{branch.to_s(true)}"}
-                else
-                  logger.trace "-> #{maybe_branch.to_s(true)}"
-                end
-              }
+              branches.each {|branch| logger.trace "-> #{branch.to_s(true)}" }
             end
           else
             raise ArgumentError, "attempt to execute without specifying a command"
@@ -317,6 +312,17 @@ module Capistrano
               exit(-1)
           end
         end
+
+        private
+        def branches_for_servers(tree,servers)
+          servers.inject([]) do |branches,server|
+            if server_branches = tree.branches_for(server)
+              branches += server_branches
+            end
+            branches
+          end
+        end
+
       end
     end
   end

test/configuration/actions/invocation_test.rb

@@ -9,6 +9,7 @@ class ConfigurationActionsInvocationTest < Test::Unit::TestCase
     attr_accessor :dry_run
     attr_accessor :preserve_roles
     attr_accessor :servers
+    attr_accessor :roles
 
     def initialize
       @options = {}
@@ -226,6 +227,37 @@ class ConfigurationActionsInvocationTest < Test::Unit::TestCase
     @config.invoke_command("ls", :once => true, :via => :foobar)
   end
 
+  def test_parallel_command_execution_with_no_match
+    assert_block("should not raise argument error") do
+      begin
+        @config.parallel do |session|
+          session.when("in?(:app)", "ls") {|ch,stream,data| puts "noop"}
+          session.when("in?(:db)", "pwd") {|ch,stream,data| puts "noop"}
+        end
+        true
+      rescue
+        false
+      end
+    end
+  end
+
+  def test_parallel_command_execution_with_matching_servers
+    @config.expects(:execute_on_servers)
+    assert_block("should not raise Argument error") do
+      begin
+        @config.servers = [:app, :db]
+        @config.roles = {:app => [:app], :db => [:db] }
+        @config.parallel do |session|
+          session.when("in?(:app)", "ls") {|ch,stream,data| puts "noop"}
+          session.when("in?(:db)", "pwd") {|ch,stream,data| puts "noop"}
+        end
+        true
+      rescue
+        false
+      end
+    end
+  end
+
   private
 
     def make_config

test/utils.rb

@@ -5,6 +5,7 @@ require 'test/unit'
 require 'mocha'
 
 require 'capistrano/server_definition'
+require 'pry'
 
 module TestExtensions
   def server(host, options={})