Add support for dependent options

lib/ddtrace/configurable.rb

@@ -41,11 +41,16 @@ def reset_options!
         end
       end
 
+      def sorted_options
+        Configuration::Resolver.new(__dependency_graph).call
+      end
+
       private
 
-      def option(name, meta = {})
+      def option(name, meta = {}, &block)
         name = name.to_sym
-        meta[:setter] ||= IDENTITY
+        meta[:setter] ||= (block || IDENTITY)
+        meta[:depends_on] ||= []
         __options[name] = meta
       end
 
@@ -65,6 +70,12 @@ def __pretty_name
 
         to_s
       end
+
+      def __dependency_graph
+        __options.each_with_object({}) do |(name, meta), graph|
+          graph[name] = meta[:depends_on]
+        end
+      end
     end
   end
 end

lib/ddtrace/configuration.rb

@@ -1,4 +1,5 @@
 require_relative 'configuration/proxy'
+require_relative 'configuration/resolver'
 
 module Datadog
   # Configuration provides a unique access point for configurations
@@ -17,8 +18,8 @@ def [](integration_name)
     def use(integration_name, options = {})
       integration = fetch_integration(integration_name)
 
-      options.each_with_object(Proxy.new(integration)) do |(name, value), proxy|
-        proxy[name] = value
+      integration.sorted_options.each do |name|
+        integration.set_option(name, options[name]) if options.key?(name)
       end
 
       integration.patch if integration.respond_to?(:patch)

lib/ddtrace/configuration/resolver.rb

@@ -0,0 +1,23 @@
+require 'tsort'
+
+module Datadog
+  class Configuration
+    class Resolver
+      include TSort
+
+      def initialize(dependency_graph = {})
+        @dependency_graph = dependency_graph
+      end
+
+      def tsort_each_node(&blk)
+        @dependency_graph.each_key(&blk)
+      end
+
+      def tsort_each_child(node, &blk)
+        @dependency_graph.fetch(node).each(&blk)
+      end
+
+      alias call tsort
+    end
+  end
+end

test/configurable_test.rb

@@ -37,6 +37,15 @@ def test_custom_setter
       assert_equal('LOUD', @module.get_option(:shout))
     end
 
+    def test_custom_setter_block
+      @module.class_eval do
+        option(:shout) { |value| value.upcase }
+      end
+
+      @module.set_option(:shout, 'loud')
+      assert_equal('LOUD', @module.get_option(:shout))
+    end
+
     def test_invalid_option
       assert_raises(InvalidOptionError) do
         @module.set_option(:bad_option, 'foo')
@@ -85,5 +94,15 @@ def test_false_options
       @module.set_option(:boolean, false)
       refute(@module.get_option(:boolean))
     end
+
+    def test_dependency_solving
+      @module.class_eval do
+        option :foo, depends_on: [:bar]
+        option :bar, depends_on: [:baz]
+        option :baz
+      end
+
+      assert_equal([:baz, :bar, :foo], @module.sorted_options)
+    end
   end
 end

test/configuration/resolver_test.rb

@@ -0,0 +1,22 @@
+require 'ddtrace/configuration'
+
+module Datadog
+  class Configuration
+    class ResolverTest < Minitest::Test
+      def test_dependency_solving
+        graph = { 1 => [2], 2 => [3, 4], 3 => [], 4 => [3], 5 => [1] }
+        tsort = Resolver.new(graph).call
+
+        assert_equal([3, 4, 2, 1, 5], tsort)
+      end
+
+      def test_cyclic_dependecy
+        graph = { 1 => [2], 2 => [1] }
+
+        assert_raises(TSort::Cyclic) do
+          Resolver.new(graph).call
+        end
+      end
+    end
+  end
+end

test/configuration_test.rb

@@ -11,6 +11,7 @@ def setup
     def test_use_method
       contrib = Minitest::Mock.new
       contrib.expect(:patch, true)
+      contrib.expect(:sorted_options, [])
 
       @registry.add(:example, contrib)
       @configuration.use(:example)
@@ -71,5 +72,21 @@ def test_hash_coercion
       @registry.add(:example, integration)
       assert_equal({ option1: :foo, option2: :bar }, @configuration[:example].to_h)
     end
+
+    def test_dependency_solving
+      integration = Module.new do
+        include Contrib::Base
+        option :multiply_by, depends_on: [:number] do |value|
+          get_option(:number) * value
+        end
+
+        option :number
+      end
+
+      @registry.add(:example, integration)
+      @configuration.use(:example, multiply_by: 5, number: 5)
+      assert_equal(5, @configuration[:example][:number])
+      assert_equal(25, @configuration[:example][:multiply_by])
+    end
   end
 end