Introduce no_release server option

In order to provide a way for a server to perform tasks as part of a
deploy but without being involved in the standard deploy flow, all
included tasks will now prefer `release_roles` over `roles`.  For
example:

    on release_roles :all do
      #
    end

This behaviour is implemented using `exclude`, a new option when
selecting roles.  `release_roles` is equivalent to:

    on roles :all, exclude: :no_release do
      #
    end

Any server defined with `no_release: true` will be excluded from these
tasks:

    server 'localhost', roles: %w{db}, no_release: true

`exclude` can also be used in user defined tasks against any attribute, for example:

    server 'localhost', roles: %w{app web}, inactive: true

    on roles :app, exclude: :inactive do
      #
    end

This commit resolves #686

lib/capistrano/configuration/server.rb

@@ -23,7 +23,7 @@ def matches?(host)
       end
 
       def select?(options)
-        selector = Selector.new(options)
+        selector = Selector.for(options)
         selector.call(self)
       end
 
@@ -103,6 +103,14 @@ def initialize(options)
           @options = options
         end
 
+        def self.for(options)
+          if options.has_key?(:exclude)
+            Exclusive
+          else
+            self
+          end.new(options)
+        end
+
         def callable
           if key.respond_to?(:call)
             key
@@ -126,6 +134,17 @@ def all
           ->(server) { :all }
         end
 
+        class Exclusive < Selector
+
+          def key
+            options[:exclude]
+          end
+
+          def call(server)
+            !callable.call(server)
+          end
+        end
+
       end
 
     end

lib/capistrano/dsl/env.rb

@@ -43,6 +43,16 @@ def roles(*names)
         env.roles_for(names)
       end
 
+      def release_roles(*names)
+        options = { exclude: :no_release }
+        if names.last.is_a? Hash
+          names.last.merge(options)
+        else
+          names << options
+        end
+        roles(*names)
+      end
+
       def primary(role)
         env.primary(role)
       end

lib/capistrano/tasks/deploy.rake

@@ -42,7 +42,7 @@ namespace :deploy do
   namespace :check do
     desc 'Check shared and release directories exist'
     task :directories do
-      on roles :all do
+      on release_roles :all do
         execute :mkdir, '-pv', shared_path, releases_path
       end
     end
@@ -80,7 +80,7 @@ namespace :deploy do
   namespace :symlink do
     desc 'Symlink release to current'
     task :release do
-      on roles :all do
+      on release_roles :all do
         execute :rm, '-rf', current_path
         execute :ln, '-s', release_path, current_path
       end
@@ -133,7 +133,7 @@ namespace :deploy do
 
   desc 'Clean up old releases'
   task :cleanup do
-    on roles :all do |host|
+    on release_roles :all do |host|
       releases = capture(:ls, '-x', releases_path).split
       if releases.count >= fetch(:keep_releases)
         info t(:keeping_releases, host: host.to_s, keep_releases: fetch(:keep_releases), releases: releases.count)

lib/capistrano/tasks/git.rake

@@ -7,7 +7,7 @@ namespace :git do
 
   desc 'Upload the git wrapper script, this script guarantees that we can script git without getting an interactive prompt'
   task :wrapper do
-    on roles :all do
+    on release_roles :all do
       upload! StringIO.new("#!/bin/sh -e\nexec /usr/bin/ssh -o PasswordAuthentication=no -o StrictHostKeyChecking=no \"$@\"\n"), "#{fetch(:tmp_dir)}/git-ssh.sh"
       execute :chmod, "+x", "#{fetch(:tmp_dir)}/git-ssh.sh"
     end
@@ -16,7 +16,7 @@ namespace :git do
   desc 'Check that the repository is reachable'
   task check: :'git:wrapper' do
     fetch(:branch)
-    on roles :all do
+    on release_roles :all do
       with git_environmental_variables do
         exit 1 unless test :git, :'ls-remote', repo_url
       end
@@ -25,7 +25,7 @@ namespace :git do
 
   desc 'Clone the repo to the cache'
   task clone: :'git:wrapper' do
-    on roles :all do
+    on release_roles :all do
       if test " [ -f #{repo_path}/HEAD ] "
         info t(:mirror_exists, at: repo_path)
       else
@@ -40,7 +40,7 @@ namespace :git do
 
   desc 'Update the repo mirror to reflect the origin state'
   task update: :'git:clone' do
-    on roles :all do
+    on release_roles :all do
       within repo_path do
         execute :git, :remote, :update
       end
@@ -49,7 +49,7 @@ namespace :git do
 
   desc 'Copy repo to releases'
   task create_release: :'git:update' do
-    on roles :all do
+    on release_roles :all do
       with git_environmental_variables do
         within repo_path do
           execute :mkdir, '-p', release_path

lib/capistrano/tasks/hg.rake

@@ -1,14 +1,14 @@
 namespace :hg do
   desc 'Check that the repo is reachable'
   task :check do
-    on roles :all do
+    on release_roles :all do
       execute "hg", "id", repo_url
     end
   end
 
   desc 'Clone the repo to the cache'
   task :clone do
-    on roles :all do
+    on release_roles :all do
       if test " [ -d #{repo_path}/.hg ] "
         info t(:mirror_exists, at: repo_path)
       else
@@ -21,7 +21,7 @@ namespace :hg do
 
   desc 'Pull changes from the remote repo'
   task :update => :'hg:clone' do
-    on roles :all do
+    on release_roles :all do
       within repo_path do
         execute "hg", "pull"
       end
@@ -30,7 +30,7 @@ namespace :hg do
 
   desc 'Copy repo to releases'
   task :create_release => :'hg:update' do
-    on roles :all do
+    on release_roles :all do
       within repo_path do
         execute "hg", "archive", release_path, "--rev", fetch(:branch)
       end

spec/integration/dsl_spec.rb

@@ -11,13 +11,33 @@
         dsl.server 'example2.com', roles: %w{web}
         dsl.server 'example3.com', roles: %w{app web}, active: true
         dsl.server 'example4.com', roles: %w{app}, primary: true
+        dsl.server 'example5.com', roles: %w{db}, no_release: true
       end
 
       describe 'fetching all servers' do
         subject { dsl.roles(:all) }
 
         it 'returns all servers' do
-          expect(subject.map(&:hostname)).to eq %w{example1.com example2.com example3.com example4.com}
+          expect(subject.map(&:hostname)).to eq %w{example1.com example2.com example3.com example4.com example5.com}
+        end
+      end
+
+      describe 'fetching all release servers' do
+
+        context 'with no additional options' do
+          subject { dsl.release_roles(:all) }
+
+          it 'returns all release servers' do
+            expect(subject.map(&:hostname)).to eq %w{example1.com example2.com example3.com example4.com}
+          end
+        end
+
+        context 'with filter options' do
+          subject { dsl.release_roles(:all, filter: :active) }
+
+          it 'returns all release servers that match the filter' do
+            expect(subject.map(&:hostname)).to eq %w{example1.com example3.com}
+          end
         end
       end
 
@@ -85,16 +105,37 @@
         dsl.role :app, %w{example3.com example4.com}
         dsl.role :app, %w{example3.com}, active: true
         dsl.role :app, %w{example4.com}, primary: true
+        dsl.role :db, %w{example5.com}, no_release: true
       end
 
       describe 'fetching all servers' do
         subject { dsl.roles(:all) }
 
         it 'returns all servers' do
-          expect(subject.map(&:hostname)).to eq %w{example1.com example2.com example3.com example4.com}
+          expect(subject.map(&:hostname)).to eq %w{example1.com example2.com example3.com example4.com example5.com}
         end
       end
 
+      describe 'fetching all release servers' do
+
+        context 'with no additional options' do
+          subject { dsl.release_roles(:all) }
+
+          it 'returns all release servers' do
+            expect(subject.map(&:hostname)).to eq %w{example1.com example2.com example3.com example4.com}
+          end
+        end
+
+        context 'with filter options' do
+          subject { dsl.release_roles(:all, filter: :active) }
+
+          it 'returns all release servers that match the filter' do
+            expect(subject.map(&:hostname)).to eq %w{example1.com example3.com}
+          end
+        end
+      end
+
+
       describe 'fetching servers by role' do
         subject { dsl.roles(:app) }
 

spec/lib/capistrano/configuration/server_spec.rb

@@ -159,6 +159,11 @@ class Configuration
               let(:options) { { select: :active }}
               it { should be_true }
             end
+
+            context 'with :exclude' do
+              let(:options) { { exclude: :active }}
+              it { should be_false }
+            end
           end
 
           context 'value does not match server properly' do
@@ -171,6 +176,11 @@ class Configuration
               let(:options) { { select: :inactive }}
               it { should be_false }
             end
+
+            context 'with :exclude' do
+              let(:options) { { exclude: :inactive }}
+              it { should be_true }
+            end
           end
         end
 
@@ -186,6 +196,12 @@ class Configuration
               let(:options) { { select: ->(s) { s.properties.active } } }
               it { should be_true }
             end
+
+            context 'with :exclude' do
+              let(:options) { { exclude: ->(s) { s.properties.active } } }
+              it { should be_false }
+            end
+
           end
 
           context 'value does not match server properly' do
@@ -198,6 +214,12 @@ class Configuration
               let(:options) { { select: ->(s) { s.properties.inactive } } }
               it { should be_false }
             end
+
+            context 'with :exclude' do
+              let(:options) { { exclude: ->(s) { s.properties.inactive } } }
+              it { should be_true }
+            end
+
           end
         end
 

spec/lib/capistrano/configuration/servers_spec.rb

@@ -141,6 +141,35 @@ class Configuration
 
       end
 
+      describe 'excluding by property' do
+
+        before do
+          servers.add_host('1', roles: :app, active: true)
+          servers.add_host('2', roles: :app, active: true, no_release: true)
+        end
+
+        it 'is empty if the filter would remove all matching hosts' do
+          hosts = servers.roles_for([:app, exclude: :active])
+          expect(hosts.map(&:hostname)).to be_empty
+        end
+
+        it 'returns the servers without the attributes specified' do
+          hosts = servers.roles_for([:app, exclude: :no_release])
+          expect(hosts.map(&:hostname)).to eq %w{1}
+        end
+
+        it 'can exclude hosts by properties on the host using a regular proc' do
+          hosts = servers.roles_for([:app, exclude: ->(h) { h.properties.no_release }])
+          expect(hosts.map(&:hostname)).to eq %w{1}
+        end
+
+        it 'is empty if the regular proc filter would remove all matching hosts' do
+          hosts = servers.roles_for([:app, exclude: ->(h) { h.properties.active }])
+          expect(hosts.map(&:hostname)).to be_empty
+        end
+
+      end
+
       describe 'filtering roles' do
 
         before do