Do not fail on first activation

lib/ruby-lsp-rails.rb

@@ -2,6 +2,8 @@
 # frozen_string_literal: true
 
 require "sorbet-runtime"
+require "pathname"
+
 require "ruby_lsp_rails/version"
 require "ruby_lsp_rails/railtie"
 

lib/ruby_lsp/ruby_lsp_rails/rails_client.rb

@@ -8,6 +8,7 @@ module RubyLsp
   module Rails
     class RailsClient
       class ServerNotRunningError < StandardError; end
+      class NeedsRestartError < StandardError; end
 
       extend T::Sig
       include Singleton
@@ -20,9 +21,19 @@ class ServerNotRunningError < StandardError; end
 
       sig { void }
       def initialize
-        @root = T.let(Dir.exist?("test/dummy") ? File.join(Dir.pwd, "test", "dummy") : Dir.pwd, String)
-        base_uri = File.read("#{@root}/tmp/app_uri.txt").chomp
+        project_root = Pathname.new(ENV["BUNDLE_GEMFILE"]).dirname
+        dummy_path = File.join(project_root, "test", "dummy")
+        @root = T.let(Dir.exist?(dummy_path) ? dummy_path : project_root.to_s, String)
+        app_uri_path = "#{@root}/tmp/app_uri.txt"
 
+        unless File.exist?(app_uri_path)
+          raise NeedsRestartError, <<~MESSAGE
+            The Ruby LSP Rails extension needs to be initialized. Please restart the Rails server and the Ruby LSP
+            to get Rails features in the editor
+          MESSAGE
+        end
+
+        base_uri = File.read(app_uri_path).chomp
         @uri = T.let("#{base_uri}/ruby_lsp_rails", String)
       end
 

test/lib/rails_client_test.rb

@@ -21,6 +21,23 @@ class RailsClientTest < ActiveSupport::TestCase
         stub_http_request("200", expected_response.to_json)
         assert_equal(expected_response, RailsClient.instance.model("User"))
       end
+
+      test "raises during instantiation if app_uri file doesn't exist" do
+        project_root = Pathname.new(ENV["BUNDLE_GEMFILE"]).dirname
+        app_uri_path = "#{project_root}/test/dummy/tmp/app_uri.txt"
+        FileUtils.rm(app_uri_path)
+
+        # If the RailsClient singleton was initialized in a different test successfully, then there would be no chance
+        # for this assertion to pass. We need to reset the singleton instance in order to force `initialize` to be
+        # executed again
+        Singleton.send(:__init__, RailsClient)
+
+        assert_raises(RailsClient::NeedsRestartError) do
+          RailsClient.instance
+        end
+      ensure
+        File.write(T.must(app_uri_path), "http://localhost:3000")
+      end
     end
   end
 end