Introduce dispatchers for adding syntax sugar to helpers

lib/dry/initializer.rb

@@ -14,6 +14,7 @@ module Initializer
     require_relative "initializer/builders"
     require_relative "initializer/config"
     require_relative "initializer/mixin"
+    require_relative "initializer/dispatchers"
 
     # Adds methods [.[]] and [.define]
     extend DSL
@@ -34,7 +35,7 @@ def dry_initializer
     # @option opts [true, false, :protected, :public, :private] :reader
     # @return [self] itself
     def param(name, type = nil, **opts)
-      dry_initializer.param(name, type, opts)
+      dry_initializer.param(name, type, Dispatchers[opts])
       self
     end
 
@@ -43,7 +44,7 @@ def param(name, type = nil, **opts)
     # @option (see #param)
     # @return (see #param)
     def option(name, type = nil, **opts)
-      dry_initializer.option(name, type, opts)
+      dry_initializer.option(name, type, Dispatchers[opts])
       self
     end
 

lib/dry/initializer/config.rb

@@ -135,7 +135,7 @@ def initialize(extended_class = nil, null: UNDEFINED)
     end
 
     def add_definition(option, name, type, opts)
-      definition = Definition.new(option, null, name, type, opts)
+      definition = Definition.new(option, null, name, type, Dispatchers[opts])
       definitions[definition.source] = definition
       finalize
 

lib/dry/initializer/dispatchers.rb

@@ -0,0 +1,44 @@
+module Dry::Initializer
+  #
+  # @private
+  #
+  # Dispatchers allow adding syntax sugar to `.param` and `.option` methods.
+  #
+  # Every dispatcher should convert the source hash of options into
+  # the resulting hash so that you can send additional keys to the helpers.
+  #
+  # @example Add special dispatcher
+  #
+  #   # Define a dispatcher for key :integer
+  #   dispatcher = proc do |opts|
+  #     opts.merge(type: proc(&:to_i)) if opts[:integer]
+  #   end
+  #
+  #   # Register a dispatcher
+  #   Dry::Initializer::Dispatchers << dispatcher
+  #
+  #   # Now you can use option `integer: true` instead of `type: proc(&:to_i)`
+  #   class Foo
+  #     extend Dry::Initializer
+  #     param :id, integer: true
+  #   end
+  #
+  module Dispatchers
+    class << self
+      def <<(item)
+        list << item
+        self
+      end
+
+      def [](options)
+        list.inject(options) { |opts, item| item.call(opts) }
+      end
+
+      private
+
+      def list
+        @list ||= []
+      end
+    end
+  end
+end

spec/custom_dispatchers_spec.rb

@@ -0,0 +1,35 @@
+describe "custom dispatchers" do
+  subject { Test::Foo.new "123" }
+
+  before do
+    dispatcher = ->(op) { op[:integer] ? op.merge(type: proc(&:to_i)) : op }
+    Dry::Initializer::Dispatchers << dispatcher
+  end
+
+  context "with extend syntax" do
+    before do
+      class Test::Foo
+        extend Dry::Initializer
+        param :id, integer: true
+      end
+    end
+
+    it "adds syntax sugar" do
+      expect(subject.id).to eq 123
+    end
+  end
+
+  context "with include syntax" do
+    before do
+      class Test::Foo
+        include Dry::Initializer.define -> do
+          param :id, integer: true
+        end
+      end
+    end
+
+    it "adds syntax sugar" do
+      expect(subject.id).to eq 123
+    end
+  end
+end