Override composer task parameters from your environment (stage|production) config file

lib/capistrano/tasks/composer.rake

@@ -1,20 +1,44 @@
 namespace :composer do
+
+desc <<-DESC
+    Check wether composer is installed globally or not.
+    This test should be executed everytime.
+  DESC
+  task :check do
+    on release_roles(fetch(:composer_roles)) do
+      info "Testing if composer is installed globally"
+      if test "[[ -n `which composer` ]]"
+        invoke 'composer:install_executable'
+      end
+    end
+  end
+
   desc <<-DESC
-    Installs composer.phar to the shared directory
-    In order to use the .phar file, the composer command needs to be mapped:
-      SSHKit.config.command_map[:composer] = "\#{shared_path.join("composer.phar")}"
+    Installs composer.phar to the composer_path directory
+    The advantage of using a variable is that we have better control on the path used in SSHKit.
+
+    In order to use the .phar file, the composer command is mapped using the composer_path variable:
+      SSHKit.config.command_map[:composer] = "php \#{fetch(composer_path)}/composer.phar"
+
     This is best used after deploy:starting:
       namespace :deploy do
         after :starting, 'composer:install_executable'
       end
   DESC
   task :install_executable do
     on release_roles(fetch(:composer_roles)) do
-      within shared_path do
+
+      within fetch(:composer_path) do
         unless test "[", "-e", "composer.phar", "]"
-          composer_version = fetch(:composer_version, nil)
-          composer_version_option = composer_version ? "-- --version=#{composer_version}" : ""
-          execute :curl, "-s", fetch(:composer_download_url), "|", :php, composer_version_option
+          set :should_install_composer, ask('Do you want to install composer locally ?', 'y|n')
+          unless fetch(:should_install_composer) != 'y'
+            composer_version = fetch(:composer_version, nil)
+            composer_version_option = composer_version ? "-- --version=#{composer_version}" : ""
+            execute :curl, "-s", fetch(:composer_download_url), "|", :php, composer_version_option
+          else
+            error("You need composer in order to continue")
+            abort()
+          end
         end
       end
     end
@@ -23,6 +47,13 @@ namespace :composer do
   task :run, :command do |t, args|
     args.with_defaults(:command => :list)
     on release_roles(fetch(:composer_roles)) do
+      if fetch(:composer_use_global)
+        execute :echo, "Using globally installed composer at ", `which composer`
+      else
+        set :composer_exec_path, "php #{fetch(:composer_path)}/composer.phar"
+        execute :echo, fetch(:composer_exec_path)
+        SSHKit.config.command_map[:composer] = fetch(:composer_exec_path)
+      end
       within fetch(:composer_working_dir) do
         execute :composer, args[:command], *args.extras
       end
@@ -57,6 +88,7 @@ namespace :composer do
     invoke "composer:run", :selfupdate, fetch(:composer_version, '')
   end
 
+  before 'composer:run', 'composer:check'
   before 'deploy:updated', 'composer:install'
   before 'deploy:reverted', 'composer:install'
 end
@@ -65,8 +97,11 @@ namespace :load do
   task :defaults do
     set :composer_install_flags, '--no-dev --prefer-dist --no-interaction --quiet --optimize-autoloader'
     set :composer_roles, :all
-    set :composer_working_dir, -> { fetch(:release_path) }
     set :composer_dump_autoload_flags, '--optimize'
     set :composer_download_url, "https://getcomposer.org/installer"
+    # use ruby global variables in a lambda
+    set :composer_working_dir, -> { "#{release_path}" }
+    set :composer_path, -> { "#{shared_path}" }
+    set :composer_use_global, false
   end
 end