Move configuration into a separate object, that can be reused for extension configuration and makes settings, their defaults, and descriptions inspectable.

middleman-core/lib/middleman-core/configuration.rb

@@ -0,0 +1,218 @@
+module Middleman
+  module Configuration
+    # Access to a global configuration manager for the whole Middleman project, 
+    # plus backwards compatibility mechanisms for older Middleman projects.
+    module Global
+      def self.included(app)
+        app.send :extend, ClassMethods
+      end
+
+      module ClassMethods
+        # Global configuration for the whole Middleman project.
+        # @return [ConfigurationManager]
+        def config
+          @_config ||= ConfigurationManager.new
+        end
+
+        # Set attributes (global variables)
+        #
+        # @deprecated Prefer accessing settings through "config".
+        #
+        # @param [Symbol] key Name of the attribue
+        # @param value Attribute value
+        # @return [void]
+        def set(key, default=nil, &block)
+          config.define_setting(key, default)
+          @inst.set(key, default, &block) if @inst
+        end
+
+        # Access global settings as methods, to preserve compatibility with
+        # old Middleman.
+        #
+        # @deprecated Prefer accessing settings through "config".
+        def method_missing(method)
+          if config.defines_setting? method
+            config[method]
+          else
+            super
+          end
+        end
+
+        # Needed so that method_missing makes sense
+        def respond_to?(method, include_private = false)
+          super || config.defines_setting?(method)
+        end
+      end
+
+      def config
+        self.class.config
+      end
+
+      # Backwards compatibilty with old Sinatra template interface
+      #
+      # @deprecated Prefer accessing settings through "config".
+      #
+      # @return [ConfigurationManager]
+      alias :settings :config
+
+      # Set attributes (global variables)
+      #
+      # @deprecated Prefer accessing settings through "config".
+      #
+      # @param [Symbol] key Name of the attribue
+      # @param value Attribute value
+      # @return [void]
+      def set(key, value=nil, &block)
+        value = block if block_given?
+        config[key] = value
+      end
+
+      # Access global settings as methods, to preserve compatibility with
+      # old Middleman.
+      #
+      # @deprecated Prefer accessing settings through "config".
+      def method_missing(method)
+        if config.defines_setting? method
+          config[method]
+        else
+          super
+        end
+      end
+
+      # Needed so that method_missing makes sense
+      def respond_to?(method, include_private = false)
+        super || config.defines_setting?(method)
+      end
+    end
+
+    # A class that manages a collection of documented settings.
+    # Can be used by extensions as well as the main Middleman
+    # application. Extensions should probably finalize their instance
+    # after defining all the settings they want to expose.
+    class ConfigurationManager
+      def initialize
+        # A hash from setting key to ConfigSetting instance.
+        @settings = {}
+        @finalized = false
+      end
+
+      # Get all settings, sorted by key, as ConfigSetting objects.
+      # @return [Array<ConfigSetting>]
+      def all_settings
+        @settings.values.sort_by(&:key)
+      end
+
+      # Get a full ConfigSetting object for the setting with the give key.
+      # @return [ConfigSetting]
+      def setting(key)
+        @settings[key]
+      end
+
+      # Get the value of a setting by key. Returns nil if there is no such setting.
+      # @return [Object]
+      def [](key)
+        setting = @settings[key]
+        setting ? setting.value : nil
+      end
+
+      # Set the value of a setting by key. Creates the setting if it doesn't exist.
+      # @param [Symbol] key
+      # @param [Object] val
+      def []=(key, val)
+        setting = @settings[key] || define_setting(key)
+        setting.value = val
+      end
+
+      # Allow configuration settings to be read and written via methods
+      def method_missing(method, *args)
+        if defines_setting?(method) && args.size == 0
+          self[method]
+        elsif method =~ /^(\w+)=$/ && args.size == 1
+          self[$1] = args[0]
+        else
+          super
+        end
+      end
+
+      # Needed so that method_missing makes sense
+      def respond_to?(method, include_private = false)
+        super || defines_setting?(method) || (method =~ /^(\w+)=$/ && defines_setting?($1))
+      end
+
+      # Does this configuration manager know about the setting identified by key?
+      # @param [Symbol] key
+      # @return [Boolean]
+      def defines_setting?(key)
+        @settings.has_key?(key)
+      end
+
+      # Define a new setting, with optional default and user-friendly description.
+      # Once the configuration manager is finalized, no new settings may be defined.
+      #
+      # @param [Symbol] key
+      # @param [Object] default
+      # @param [String] description
+      # @return [ConfigSetting]
+      def define_setting(key, default=nil, description=nil)
+        raise "Setting #{key} doesn't exist" if @finalized
+        raise "Setting #{key} already defined" if @settings.has_key?(key)
+        raise "Setting key must be a Symbol" unless key.is_a? Symbol
+
+        @settings[key] = ConfigSetting.new(key, default, description)
+      end
+
+      # Switch the configuration manager is finalized, it switches to read-only
+      # mode and no new settings may be defined.
+      def finalize!
+        @finalized = true
+      end
+
+      # Deep duplicate of the configuration manager
+      def dup
+        copy = ConfigurationManager.new
+        @settings.each do |key, setting|
+          copy_setting = copy.define_setting setting.key, setting.default, setting.description
+          copy_setting.value = setting.value if setting.value_set?
+        end
+        copy
+      end
+
+      def to_h
+        hash = {}
+        @settings.each do |key, setting|
+          hash[key] = setting.value
+        end
+        hash
+      end
+
+      def to_s
+        to_h.inspect
+      end
+    end
+
+    class ConfigSetting
+      attr_accessor :key, :default, :description
+      attr_writer :value
+
+      def initialize(key, default, description)
+        @value_set = false
+        self.key = key
+        self.default = default
+        self.description = description
+      end
+
+      def value=(value)
+        @value = value
+        @value_set = true
+      end
+
+      def value
+        value_set? ? @value : default
+      end
+
+      def value_set?
+        @value_set
+      end
+    end
+  end
+end