Allow independent configurations to require the same recipe file (closes #9367)

git-svn-id: http://svn.rubyonrails.org/rails/tools/capistrano@7389 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Allow independent configurations to require the same recipe file [Jamis Buck]
+
 * Set :shell to false to run a command without wrapping it in "sh -c" [Jamis Buck]
 
 * Don't request a pty by default [Jamis Buck]

lib/capistrano/configuration/loading.rb

@@ -25,6 +25,28 @@ module Capistrano
         def instance=(config)
           Thread.current[:capistrano_configuration] = config
         end
+
+        # Used internally by Capistrano to track which recipes have been loaded
+        # via require, so that they may be successfully reloaded when require
+        # is called again.
+        def recipes_per_feature
+          @recipes_per_feature ||= {}
+        end
+
+        # Used internally to determine what the current "feature" being
+        # required is. This is used to track which files load which recipes
+        # via require.
+        def current_feature
+          Thread.current[:capistrano_current_feature]
+        end
+
+        # Used internally to specify the current file being required, so that
+        # any recipes loaded by that file can be remembered. This allows
+        # recipes loaded via require to be correctly reloaded in different
+        # Configuration instances in the same Ruby instance.
+        def current_feature=(feature)
+          Thread.current[:capistrano_current_feature] = feature
+        end
       end
 
       # The load paths used for locating recipe files.
@@ -33,6 +55,7 @@ module Capistrano
       def initialize_with_loading(*args) #:nodoc:
         initialize_without_loading(*args)
         @load_paths = [".", File.expand_path(File.join(File.dirname(__FILE__), "../recipes"))]
+        @loaded_features = []
       end
       private :initialize_with_loading
 
@@ -66,9 +89,11 @@ module Capistrano
           load_from_file(options[:file], options[:name])
 
         elsif options[:string]
+          remember_load(options) unless options[:reloading]
           instance_eval(options[:string], options[:name] || "<eval>")
 
         elsif options[:proc]
+          remember_load(options) unless options[:reloading]
           instance_eval(&options[:proc])
 
         else
@@ -80,12 +105,63 @@ module Capistrano
       # with the exception that it sets the receiver as the "current" configuration
       # so that third-party task bundles can include themselves relative to
       # that configuration.
+      #
+      # This is a bit more complicated than an initial review would seem to
+      # necessitate, but the use case that complicates things is this: An
+      # advanced user wants to embed capistrano, and needs to instantiate
+      # more than one capistrano configuration at a time. They also want each
+      # configuration to require a third-party capistrano extension. Using a
+      # naive require implementation, this would allow the first configuration
+      # to successfully load the third-party extension, but the require would
+      # fail for the second configuration because the extension has already
+      # been loaded.
+      #
+      # To work around this, we do a few things:
+      #
+      # 1. Each time a 'require' is invoked inside of a capistrano recipe,
+      #    we remember the arguments (see "current_feature").
+      # 2. Each time a 'load' is invoked inside of a capistrano recipe, and
+      #    "current_feature" is not nil (meaning we are inside of a pending
+      #    require) we remember the options (see "remember_load" and
+      #    "recipes_per_feature").
+      # 3. Each time a 'require' is invoked inside of a capistrano recipe,
+      #    we check to see if this particular configuration has ever seen these
+      #    arguments to require (see @loaded_features), and if not, we proceed
+      #    as if the file had never been required. If the superclass' require
+      #    returns false (meaning, potentially, that the file has already been
+      #    required), then we look in the recipes_per_feature collection and
+      #    load any remembered recipes from there.
+      #
+      # It's kind of a bear, but it works, and works transparently. Note that
+      # a simpler implementation would just muck with $", allowing files to be
+      # required multiple times, but that will cause warnings (and possibly
+      # errors) if the file to be required contains constant definitions and
+      # such, alongside (or instead of) capistrano recipe definitions.
       def require(*args) #:nodoc:
-        original, self.class.instance = self.class.instance, self
-        super
-      ensure
-        # restore the original, so that require's can be nested
-        self.class.instance = original
+        # look to see if this specific configuration instance has ever seen
+        # these arguments to require before
+        if !@loaded_features.include?(args)
+          @loaded_features << args
+
+          begin
+            original_instance, self.class.instance = self.class.instance, self
+            original_feature, self.class.current_feature = self.class.current_feature, args
+
+            result = super
+            if !result # file has been required previously, load up the remembered recipes
+              list = self.class.recipes_per_feature[args] || []
+              list.each { |options| load(options.merge(:reloading => true)) }
+            end
+
+            return result
+          ensure
+            # restore the original, so that require's can be nested
+            self.class.instance = original_instance
+            self.class.current_feature = original_feature
+          end
+        else
+          return false
+        end
       end
 
       private
@@ -107,6 +183,16 @@ module Capistrano
 
           raise LoadError, "no such file to load -- #{file}"
         end
+
+        # If a file is being required, the options associated with loading a
+        # recipe are remembered in the recipes_per_feature archive under the
+        # name of the file currently being required.
+        def remember_load(options)
+          if self.class.current_feature
+            list = (self.class.recipes_per_feature[self.class.current_feature] ||= [])
+            list << options
+          end
+        end
     end
   end
 end

test/configuration/loading_test.rb

@@ -116,4 +116,12 @@ class ConfigurationLoadingTest < Test::Unit::TestCase
       require "#{File.dirname(__FILE__)}/../fixtures/custom"
     end
   end
+
+  def test_require_in_multiple_instances_should_load_recipes_in_each_instance
+    config2 = MockConfig.new
+    @config.require "#{File.dirname(__FILE__)}/../fixtures/custom"
+    config2.require "#{File.dirname(__FILE__)}/../fixtures/custom"
+    assert_equal :custom, @config.ping
+    assert_equal :custom, config2.ping
+  end
 end