Merge pull request #3490 from sambostock/dynamic-dispatch

 Dynamically register events to dispatch

Author: kddnewton

sig/prism/dispatcher.rbs

@@ -4,9 +4,12 @@ module Prism
 
     def initialize: () -> void
     def register: (untyped, *Symbol) -> void
+    def register_public_methods: (untyped) -> void
     def dispatch: (Prism::node) -> void
     def dispatch_once: (Prism::node) -> void
 
+    private def register_events: (untyped, Array[Symbol]) -> void
+
     class DispatchOnce < Visitor
       attr_reader listeners: Hash[Symbol, Array[untyped]]
 

templates/lib/prism/dispatcher.rb.erb

@@ -44,6 +44,19 @@ module Prism
     #
     # def register: (Listener, *Symbol) -> void
     def register(listener, *events)
+      register_events(listener, events)
+    end
+
+    # Register all public methods of a listener that match the pattern
+    # `on_<node_name>_(enter|leave)`.
+    #
+    # def register_public_methods: (Listener) -> void
+    def register_public_methods(listener)
+      register_events(listener, listener.public_methods(false).grep(/\Aon_.+_(?:enter|leave)\z/))
+    end
+
+    # Register a listener for the given events.
+    private def register_events(listener, events)
       events.each { |event| (listeners[event] ||= []) << listener }
     end
 

test/prism/ruby/dispatcher_test.rb

@@ -25,9 +25,12 @@ def on_integer_node_enter(node)
     end
 
     def test_dispatching_events
-      listener = TestListener.new
+      listener_manual = TestListener.new
+      listener_public = TestListener.new
+
       dispatcher = Dispatcher.new
-      dispatcher.register(listener, :on_call_node_enter, :on_call_node_leave, :on_integer_node_enter)
+      dispatcher.register(listener_manual, :on_call_node_enter, :on_call_node_leave, :on_integer_node_enter)
+      dispatcher.register_public_methods(listener_public)
 
       root = Prism.parse(<<~RUBY).value
         def foo
@@ -36,11 +39,17 @@ def foo
       RUBY
 
       dispatcher.dispatch(root)
-      assert_equal([:on_call_node_enter, :on_integer_node_enter, :on_integer_node_enter, :on_integer_node_enter, :on_call_node_leave], listener.events_received)
 
-      listener.events_received.clear
+      [listener_manual, listener_public].each do |listener|
+        assert_equal([:on_call_node_enter, :on_integer_node_enter, :on_integer_node_enter, :on_integer_node_enter, :on_call_node_leave], listener.events_received)
+        listener.events_received.clear
+      end
+
       dispatcher.dispatch_once(root.statements.body.first.body.body.first)
-      assert_equal([:on_call_node_enter, :on_call_node_leave], listener.events_received)
+
+      [listener_manual, listener_public].each do |listener|
+        assert_equal([:on_call_node_enter, :on_call_node_leave], listener.events_received)
+      end
     end
   end
 end