Add workflow capabilities DSL

lib/r3x/workflow.rb

@@ -1,12 +1,15 @@
 module R3x
   module Workflow
+    KNOWN_CAPABILITIES = Set.new(%i[networking filesystem shell]).freeze
+
     module Dsl
       extend ActiveSupport::Concern
 
       class_methods do
         def inherited(subclass)
           super
           subclass._triggers = TriggerManager::Collection.new
+          subclass._capabilities = Set.new
         end
 
         def workflow_key
@@ -19,6 +22,25 @@ def trigger(type, **options)
           _triggers.add(trigger_instance)
         end
 
+        def uses(*capabilities)
+          incoming = Set.new(capabilities.flatten.compact.map(&:to_sym))
+          unknown = incoming - KNOWN_CAPABILITIES
+          raise ArgumentError, "Unknown capabilities: #{unknown.to_a.join(", ")}. Known: #{KNOWN_CAPABILITIES.to_a.join(", ")}" if unknown.any?
+
+          duplicates = incoming & _capabilities
+          raise ArgumentError, "Capability already declared: #{duplicates.to_a.join(", ")}" if duplicates.any?
+
+          _capabilities.merge(incoming)
+        end
+
+        def capabilities
+          _capabilities.dup
+        end
+
+        def uses?(capability)
+          _capabilities.include?(capability.to_sym)
+        end
+
         # Returns all triggers, with a default Manual trigger if none declared
         def triggers
           triggers = _triggers.to_a
@@ -38,6 +60,7 @@ def triggers_by_key
         end
 
         attr_accessor :_triggers
+        attr_accessor :_capabilities
       end
     end
   end

test/lib/r3x/workflow_test.rb

@@ -101,6 +101,50 @@ def self.name
       assert_equal [ :schedule ], triggers.map(&:type)
     end
 
+    test "uses declares workflow capabilities" do
+      klass = Class.new(R3x::Workflow::Base) do
+        def self.name
+          "Workflows::NetworkedWorkflow"
+        end
+
+        uses :networking
+      end
+
+      assert_equal Set.new([ :networking ]), klass.capabilities
+      assert klass.uses?(:networking)
+      refute klass.uses?(:filesystem)
+    end
+
+    test "uses raises on duplicate capability" do
+      klass = Class.new(R3x::Workflow::Base) do
+        def self.name
+          "Workflows::DuplicateCap"
+        end
+
+        uses :networking
+      end
+
+      error = assert_raises(ArgumentError) do
+        klass.uses(:networking)
+      end
+
+      assert_match "Capability already declared", error.message
+    end
+
+    test "uses raises on unknown capability" do
+      error = assert_raises(ArgumentError) do
+        Class.new(R3x::Workflow::Base) do
+          def self.name
+            "Workflows::BadCap"
+          end
+
+          uses :hacking
+        end
+      end
+
+      assert_match "Unknown capabilities: hacking", error.message
+    end
+
     test "trigger :schedule rejects blank cron (empty string and whitespace)" do
       [
         "",