Allow declaration of project addons

jekyll/add-ons.markdown

@@ -61,6 +61,10 @@ The Ruby LSP discovers add-ons based on the existence of an `addon.rb` file plac
 example, `my_gem/lib/ruby_lsp/my_gem/addon.rb`. This file must declare the add-on class, which can be used to perform any
 necessary activation when the server starts.
 
+{: .note }
+Projects can also define their own private add-ons for functionality that only applies to a particular application. As
+long as a file matching `ruby_lsp/**/addon.rb` exists inside of the workspace (not necessarily at the root), it will be
+loaded by the Ruby LSP.
 
 ```ruby
 # frozen_string_literal: true

lib/ruby_indexer/lib/ruby_indexer/configuration.rb

@@ -239,6 +239,8 @@ def initial_excluded_gems
 
       excluded.uniq!
       excluded.map(&:name)
+    rescue Bundler::GemfileNotFound
+      []
     end
   end
 end

lib/ruby_lsp/addon.rb

@@ -54,14 +54,19 @@ def inherited(child_class)
       end
 
       # Discovers and loads all add-ons. Returns a list of errors when trying to require add-ons
-      sig do
-        params(global_state: GlobalState, outgoing_queue: Thread::Queue).returns(T::Array[StandardError])
-      end
+      sig { params(global_state: GlobalState, outgoing_queue: Thread::Queue).returns(T::Array[StandardError]) }
       def load_addons(global_state, outgoing_queue)
         # Require all add-ons entry points, which should be placed under
-        # `some_gem/lib/ruby_lsp/your_gem_name/addon.rb`
-        errors = Gem.find_files("ruby_lsp/**/addon.rb").filter_map do |addon|
-          require File.expand_path(addon)
+        # `some_gem/lib/ruby_lsp/your_gem_name/addon.rb` or in the workspace under
+        # `your_project/ruby_lsp/project_name/addon.rb`
+        errors = Gem.find_files("ruby_lsp/**/addon.rb")
+          .concat(Dir.glob(File.join(global_state.workspace_path, "**", "ruby_lsp/**/addon.rb")))
+          .filter_map do |addon_path|
+          # Avoid requiring this file twice. This may happen if you're working on the Ruby LSP itself and at the same
+          # time have `ruby-lsp` installed as a vendored gem
+          next if addon_path.end_with?("lib/ruby_lsp/addon.rb")
+
+          require File.expand_path(addon_path)
           nil
         rescue => e
           e
@@ -90,6 +95,10 @@ def load_addons(global_state, outgoing_queue)
       # the responsibility of the add-ons using this API to handle these errors appropriately.
       sig { params(addon_name: String, version_constraints: String).returns(Addon) }
       def get(addon_name, *version_constraints)
+        if version_constraints.empty?
+          raise IncompatibleApiError, "Must specify version constraints when accessing other add-ons"
+        end
+
         addon = addons.find { |addon| addon.name == addon_name }
         raise AddonNotFoundError, "Could not find add-on '#{addon_name}'" unless addon
 

test/addon_test.rb

@@ -126,6 +126,12 @@ def test_raises_if_an_addon_version_does_not_match
       end
     end
 
+    def test_raises_if_no_version_constraints_are_passed
+      assert_raises(Addon::IncompatibleApiError) do
+        Addon.get("My Add-on")
+      end
+    end
+
     def test_addons_receive_settings
       global_state = GlobalState.new
       global_state.apply_options({
@@ -153,5 +159,44 @@ def test_depend_on_constraints
 
       Addon.depend_on_ruby_lsp!(">= 0.18.0", "< 0.30.0")
     end
+
+    def test_project_specific_addons
+      Dir.mktmpdir do |dir|
+        Dir.chdir(dir) do
+          addon_dir = File.join(dir, "lib", "ruby_lsp", "test_addon")
+          FileUtils.mkdir_p(addon_dir)
+          File.write(File.join(addon_dir, "addon.rb"), <<~RUBY)
+            class ProjectAddon < RubyLsp::Addon
+              attr_reader :hello
+
+              def activate(global_state, outgoing_queue)
+                @hello = true
+              end
+
+              def name
+                "Project Addon"
+              end
+
+              def version
+                "0.1.0"
+              end
+            end
+          RUBY
+
+          queue = Thread::Queue.new
+          global_state = GlobalState.new
+          global_state.apply_options({
+            workspaceFolders: [{ uri: URI::Generic.from_path(path: dir).to_s }],
+          })
+          Addon.load_addons(global_state, queue)
+
+          addon = Addon.get("Project Addon", "0.1.0")
+          assert_equal("Project Addon", addon.name)
+          assert_predicate(T.unsafe(addon), :hello)
+        ensure
+          T.must(queue).close
+        end
+      end
+    end
   end
 end