Add launcher executable

exe/ruby-lsp

@@ -33,6 +33,10 @@ parser = OptionParser.new do |opts|
     options[:doctor] = true
   end
 
+  opts.on("--use-launcher", "Use launcher mechanism to handle missing dependencies gracefully") do
+    options[:launcher] = true
+  end
+
   opts.on("-h", "--help", "Print this help") do
     puts opts.help
     puts
@@ -54,6 +58,17 @@ end
 # using `BUNDLE_GEMFILE=.ruby-lsp/Gemfile bundle exec ruby-lsp` so that we have access to the gems that are a part of
 # the application's bundle
 if ENV["BUNDLE_GEMFILE"].nil?
+  # Substitute the current process by the launcher. Rubygems activates all dependencies of a gem's executable eagerly,
+  # but we can't have that happen because we want to invoke Bundler.setup ourselves with the composed bundle and avoid
+  # duplicate spec activation errors. Replacing the process with the launcher executable will clear the activated specs,
+  # which gives us the opportunity to control which specs are activated and enter degraded mode if any gems failed to
+  # install rather than failing to boot the server completely
+  if options[:launcher]
+    command = +File.expand_path("ruby-lsp-launcher", __dir__)
+    command << " --debug" if options[:debug]
+    exit exec(command)
+  end
+
   require_relative "../lib/ruby_lsp/setup_bundler"
 
   begin
@@ -72,9 +87,9 @@ if ENV["BUNDLE_GEMFILE"].nil?
   exit exec(env, "#{base_bundle} exec ruby-lsp #{original_args.join(" ")}")
 end
 
-require "ruby_lsp/load_sorbet"
-
 $LOAD_PATH.unshift(File.expand_path("../lib", __dir__))
+
+require "ruby_lsp/load_sorbet"
 require "ruby_lsp/internal"
 
 T::Utils.run_all_sig_blocks

exe/ruby-lsp-launcher

@@ -0,0 +1,94 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+# !!!!!!!
+# No gems can be required in this file until we invoke bundler setup except inside the forked process that sets up the
+# composed bundle
+# !!!!!!!
+
+setup_error = nil
+
+# Read the initialize request before even starting the server. We need to do this to figure out the workspace URI.
+# Editors are not required to spawn the language server process on the same directory as the workspace URI, so we need
+# to ensure that we're setting up the bundle in the right place
+$stdin.binmode
+headers = $stdin.gets("\r\n\r\n")
+content_length = headers[/Content-Length: (\d+)/i, 1].to_i
+raw_initialize = $stdin.read(content_length)
+
+bundle_gemfile_file = File.join(".ruby-lsp", "bundle_gemfile")
+
+# Composed the Ruby LSP bundle in a forked process so that we can require gems without polluting the main process
+# `$LOAD_PATH` and `Gem.loaded_specs`
+pid = fork do
+  require_relative "../lib/ruby_lsp/setup_bundler"
+  require "json"
+  require "uri"
+  require "core_ext/uri"
+
+  initialize_request = JSON.parse(raw_initialize, symbolize_names: true)
+  workspace_uri = initialize_request.dig(:params, :workspaceFolders, 0, :uri)
+  workspace_path = workspace_uri && URI(workspace_uri).to_standardized_path
+  workspace_path ||= Dir.pwd
+
+  env = RubyLsp::SetupBundler.new(workspace_path).setup!
+  File.write(bundle_gemfile_file, env["BUNDLE_GEMFILE"])
+rescue RubyLsp::SetupBundler::BundleNotLocked
+  warn("Project contains a Gemfile, but no Gemfile.lock. Run `bundle install` to lock gems and restart the server")
+end
+
+# Wait until the composed Bundle is finished
+Process.wait(pid)
+
+begin
+  require "bundler"
+  Bundler.ui.level = :silent
+
+  # The composed bundle logic informs the main process about which Gemfile to setup Bundler with
+  if File.exist?(bundle_gemfile_file)
+    ENV["BUNDLE_GEMFILE"] = File.read(bundle_gemfile_file)
+    Bundler.setup
+  end
+rescue StandardError => e
+  # If installing gems failed for any reason, we don't want to exit the process prematurely. We can still provide most
+  # features in a degraded mode. We simply save the error so that we can report to the user that certain gems might be
+  # missing, but we respect the LSP life cycle
+  setup_error = e
+
+  # If we failed to setup the bundle, the minimum we need is to have our own dependencies activated so that we can
+  # require the gems the LSP depends on. If even that fails, then there's no way we can continue to run the language
+  # server
+  Gem::Specification.find_by_name("ruby-lsp").activate
+end
+
+# Now that the bundle is set up, we can begin actually launching the server
+
+$LOAD_PATH.unshift(File.expand_path("../lib", __dir__))
+
+require "ruby_lsp/load_sorbet"
+require "ruby_lsp/internal"
+
+T::Utils.run_all_sig_blocks
+
+if ARGV.include?("--debug")
+  if ["x64-mingw-ucrt", "x64-mingw32"].include?(RUBY_PLATFORM)
+    $stderr.puts "Debugging is not supported on Windows"
+  else
+    begin
+      ENV.delete("RUBY_DEBUG_IRB_CONSOLE")
+      require "debug/open_nonstop"
+    rescue LoadError
+      $stderr.puts("You need to install the debug gem to use the --debug flag")
+    end
+  end
+end
+
+# Ensure all output goes out stderr by default to allow puts/p/pp to work without specifying output device.
+$> = $stderr
+
+initialize_request = JSON.parse(raw_initialize, symbolize_names: true) if raw_initialize
+
+RubyLsp::Server.new(
+  setup_error: setup_error,
+  initialize_request: initialize_request,
+).start

lib/ruby_lsp/internal.rb

@@ -12,6 +12,7 @@
 require "bundler"
 Bundler.ui.level = :silent
 
+require "json"
 require "uri"
 require "cgi"
 require "set"

ruby-lsp.gemspec

@@ -15,7 +15,7 @@ Gem::Specification.new do |s|
 
   s.files = Dir.glob("lib/**/*.rb") + ["README.md", "VERSION", "LICENSE.txt"] + Dir.glob("static_docs/**/*.md")
   s.bindir = "exe"
-  s.executables = ["ruby-lsp", "ruby-lsp-check"]
+  s.executables = ["ruby-lsp", "ruby-lsp-check", "ruby-lsp-launcher"]
   s.require_paths = ["lib"]
 
   # Dependencies must be kept in sync with the checks in the extension side on workspace.ts