Allow extensions to optionally register to be automatically activated before configuration.

middleman-core/lib/middleman-core/core_extensions/extensions.rb

@@ -86,6 +86,10 @@ module Middleman
 
         ::Middleman::Extension.clear_after_extension_callbacks
 
+        ::Middleman::Extensions.auto_activate_before_configuration.each do |ext_name|
+          activate ext_name
+        end
+
         if ENV['AUTOLOAD_SPROCKETS'] != 'false'
           begin
             require 'middleman-sprockets'

middleman-core/lib/middleman-core/extensions.rb

@@ -1,4 +1,5 @@
 require 'middleman-core/extension'
+require 'set'
 
 module Middleman
   # The Extensions module is used to handle global registration and loading of Middleman Extensions.
@@ -7,13 +8,19 @@ module Middleman
   # `middleman-core/core_extensions/extensions.rb`.
   module Extensions
     @registered = {}
+    @auto_activate_before_configuration = Set.new
 
     class << self
+      # @api private
       # A hash of all registered extensions. Registered extensions are not necessarily active - this
       # is the set of all extensions that are known to Middleman.
       # @return [Hash{Symbol => Class<Middleman::Extension>, Proc}] A directory of known extensions indexed by the name they were registered under. The value may be a Proc, which can be lazily called to return an extension class.
       attr_reader :registered
 
+      # @api private
+      # A list of extensions that should be automatically loaded before `config.rb` is loaded and before the `:before_configuration` hook is run. Only internal, built-in Middleman extensions should be listed here.
+      attr_reader :auto_activate_before_configuration
+
       # Register a new extension. Choose a name which will be
       # used to activate the extension in `config.rb`, like this:
       #
@@ -32,16 +39,25 @@ module Middleman
       #
       # @param [Symbol] name The name of the extension
       # @param [Class<Middleman::Extension>] extension_class The extension class (Must inherit from {Middleman::Extension})
+      # @option options [Boolean] :auto_activate_before_configuration If set to true, this extension will be automatically
+      #         activated before `config.rb` is loaded and before the `:before_configuration` hook is run.
+      #         This is intended for use with built-in Middleman extensions and should not be used by third-party extensions.
       # @yield Instead of passing a module in namespace, you can provide
       #        a block which returns your extension class. This gives
       #        you the ability to require other files only when the
       #        extension is first activated.
       # @return [void]
-      def register(name, extension_class=nil, &block)
+      def register(name, extension_class=nil, options={}, &block)
         raise 'Extension name must be a symbol' unless name.is_a?(Symbol)
         # If we've already got an extension registered under this name, bail out
         raise "There is already an extension registered with the name '#{name}'" if registered.key?(name)
 
+        # If the extension is defined with a block, grab options out of the "extension_class" parameter.
+        if extension_class && block_given? && options.empty? && extension_class.is_a?(Hash)
+          options = extension_class
+          extension_class = nil
+        end
+
         registered[name] = if block_given?
           block
         elsif extension_class && extension_class.ancestors.include?(::Middleman::Extension)
@@ -49,6 +65,8 @@ module Middleman
         else
           raise 'You must provide a Middleman::Extension or a block that returns a Middleman::Extension'
         end
+
+        @auto_activate_before_configuration << name if options[:auto_activate_before_configuration]
       end
 
       # @api private

middleman-core/lib/middleman-core/meta_pages.rb

@@ -63,6 +63,8 @@ module Middleman
         extension_config = {}
 
         @middleman.inst.extensions.each do |ext_name, extension|
+          next if ::Middleman::Extension.auto_activate_before_configuration.include? ext_name
+
           if extension.is_a?(Hash)
             # Multiple instance extension
             if extension.size == 1
@@ -72,10 +74,8 @@ module Middleman
                 extension_config["#{ext_name} (#{inst})"] = extension_options(ext)
               end
             end
-          elsif extension.is_a?(::Middleman::Extension)
-            extension_config[ext_name] = extension_options(extension)
           else
-            extension_config[ext_name] = nil
+            extension_config[ext_name] = extension_options(extension)
           end
         end