Adds engines 2.1.0 plugin.

git-svn-id: http://redmine.rubyforge.org/svn/trunk@1654 e93f8b46-1217-0410-a6f0-8f06a7374b81

vendor/plugins/engines/generators/plugin_migration/USAGE

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+Description:
+  The plugin migration generator assists in working with schema additions 
+  required by plugins. Instead of running migrations from plugins directly,
+  the generator creates a regular Rails migration which will be responsible
+  for migrating the plugins from their current version to the latest version
+  installed.
+  
+  This is important because the set of application migrations remains an
+  accurate record of the state of the database, even as plugins are installed
+  and removed during the development process.
+
+Example:
+  ./script/generate plugin_migration [<plugin_name> <another_plugin_name> ...]
+
+  This will generate:
+
+    RAILS_ROOT
+      |- db
+          |-migrate
+              |- xxx_plugin_migrations.rb
+
+  which contains the migrations for the given plugin(s).
+  
+  
+Advanced Usage:
+
+There may be situations where you need *complete* control over the migrations
+of plugins in your application, migrating a certainly plugin down to X, and
+another plugin up to Y, where neither X or Y are the latest migrations for those
+plugins.
+
+For those unfortunate few, I have two pieces of advice:
+
+ 1. Why? This is a code smell [http://c2.com/xp/CodeSmell.html].
+ 
+ 2. Well, OK. Don't panic. You can completely control plugin migrations by
+    creating your own migrations. To manually migrate a plugin to a specific
+    version, simply use
+    
+      Engines.plugins[:your_plugin_name].migrate(version)
+      
+    where version is the integer of the migration this plugin should end
+    up at.
+    
+With great power comes great responsibility. Use this wisely.

vendor/plugins/engines/generators/plugin_migration/plugin_migration_generator.rb

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+# Generates a migration which migrates all plugins to their latest versions
+# within the database.
+class PluginMigrationGenerator < Rails::Generator::Base
+  
+  def initialize(runtime_args, runtime_options={})
+    super
+    @options = {:assigns => {}}
+    
+    ensure_plugin_schema_table_exists
+    get_plugins_to_migrate(runtime_args)
+    
+    if @plugins_to_migrate.empty?
+      puts "All plugins are migrated to their latest versions"
+      exit(0)
+    end
+
+    @options[:migration_file_name] = build_migration_name
+    @options[:assigns][:class_name] = build_migration_name.classify
+  end
+  
+  def manifest
+    record do |m|
+      m.migration_template 'plugin_migration.erb', 'db/migrate', @options
+    end
+  end
+  
+  protected
+  
+    # Create the plugin schema table if it doesn't already exist. See
+    # Engines::RailsExtensions::Migrations#initialize_schema_migrations_table_with_engine_additions
+    def ensure_plugin_schema_table_exists
+      ActiveRecord::Base.connection.initialize_schema_migrations_table
+    end
+
+    # Determine all the plugins which have migrations that aren't present
+    # according to the plugin schema information from the database.
+    def get_plugins_to_migrate(plugin_names)
+
+      # First, grab all the plugins which exist and have migrations
+      @plugins_to_migrate = if plugin_names.empty?
+        Engines.plugins
+      else
+        plugin_names.map do |name| 
+          Engines.plugins[name] ? Engines.plugins[name] : raise("Cannot find the plugin '#{name}'")
+        end
+      end
+      
+      @plugins_to_migrate.reject! { |p| p.latest_migration.nil? }
+      
+      # Then find the current versions from the database    
+      @current_versions = {}
+      @plugins_to_migrate.each do |plugin|
+        @current_versions[plugin.name] = Engines::Plugin::Migrator.current_version(plugin)
+      end
+
+      # Then find the latest versions from their migration directories
+      @new_versions = {}      
+      @plugins_to_migrate.each do |plugin|
+        @new_versions[plugin.name] = plugin.latest_migration
+      end
+      
+      # Remove any plugins that don't need migration
+      @plugins_to_migrate.map { |p| p.name }.each do |name|
+        @plugins_to_migrate.delete(Engines.plugins[name]) if @current_versions[name] == @new_versions[name]
+      end
+      
+      @options[:assigns][:plugins] = @plugins_to_migrate
+      @options[:assigns][:new_versions] = @new_versions
+      @options[:assigns][:current_versions] = @current_versions
+    end
+
+    # Construct a unique migration name based on the plugins involved and the
+    # versions they should reach after this migration is run.
+    def build_migration_name
+      @plugins_to_migrate.map do |plugin| 
+        "#{plugin.name}_to_version_#{@new_versions[plugin.name]}" 
+      end.join("_and_")
+    end  
+end

vendor/plugins/engines/generators/plugin_migration/templates/plugin_migration.erb

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+class <%= class_name %> < ActiveRecord::Migration
+  def self.up
+  <%- plugins.each do |plugin| -%>
+    Engines.plugins["<%= plugin.name %>"].migrate(<%= new_versions[plugin.name] %>)
+  <%- end -%>
+  end
+
+  def self.down
+  <%- plugins.each do |plugin| -%>
+    Engines.plugins["<%= plugin.name %>"].migrate(<%= current_versions[plugin.name] %>)
+  <%- end -%>
+  end
+end