Allow addons to register for filewatching events (#1464)

* Allow addons to register for filewatching events

* Extend from Addon

---------

Co-authored-by: Andy Waite <andyw8@users.noreply.github.com>

lib/ruby_lsp/addon.rb

@@ -27,13 +27,18 @@ class Addon
 
     @addons = T.let([], T::Array[Addon])
     @addon_classes = T.let([], T::Array[T.class_of(Addon)])
+    # Addon instances that have declared a handler to accept file watcher events
+    @file_watcher_addons = T.let([], T::Array[Addon])
 
     class << self
       extend T::Sig
 
       sig { returns(T::Array[Addon]) }
       attr_accessor :addons
 
+      sig { returns(T::Array[Addon]) }
+      attr_accessor :file_watcher_addons
+
       sig { returns(T::Array[T.class_of(Addon)]) }
       attr_reader :addon_classes
 
@@ -57,6 +62,7 @@ def load_addons(message_queue)
 
         # Instantiate all discovered addon classes
         self.addons = addon_classes.map(&:new)
+        self.file_watcher_addons = addons.select { |addon| addon.respond_to?(:workspace_did_change_watched_files) }
 
         # Activate each one of the discovered addons. If any problems occur in the addons, we don't want to
         # fail to boot the server

lib/ruby_lsp/executor.rb

@@ -229,6 +229,7 @@ def did_change_watched_files(changes)
         end
       end
 
+      Addon.file_watcher_addons.each { |addon| T.unsafe(addon).workspace_did_change_watched_files(changes) }
       VOID
     end
 

test/addon_test.rb

@@ -76,5 +76,24 @@ def name
           Failed to activate
       MESSAGE
     end
+
+    def test_automatically_identifies_file_watcher_addons
+      klass = Class.new(::RubyLsp::Addon) do
+        def activate(message_queue); end
+        def deactivate; end
+
+        def workspace_did_change_watched_files(changes); end
+      end
+
+      begin
+        queue = Thread::Queue.new
+        Addon.load_addons(queue)
+        assert_equal(1, Addon.file_watcher_addons.length)
+        assert_instance_of(klass, Addon.file_watcher_addons.first)
+      ensure
+        T.must(queue).close
+        Addon.file_watcher_addons.clear
+      end
+    end
   end
 end