Add Ruby LSP extension for hover

Author: vinistock

.rubocop.yml

@@ -10,6 +10,8 @@ AllCops:
   NewCops: disable
   SuggestExtensions: false
   TargetRubyVersion: 2.7
+  Exclude:
+    - "test/dummy/db/**/*.rb"
 
 Sorbet/FalseSigil:
   Enabled: false

Gemfile

@@ -17,3 +17,5 @@ gem "rubocop-sorbet", "~> 0.7", require: false
 
 gem "sorbet-static-and-runtime"
 gem "tapioca", "~> 0.11", require: false
+
+gem "ruby-lsp", path: "../ruby-lsp"

Gemfile.lock

@@ -1,3 +1,11 @@
+PATH
+  remote: ../ruby-lsp
+  specs:
+    ruby-lsp (0.4.3)
+      language_server-protocol (~> 3.17.0)
+      sorbet-runtime
+      syntax_tree (>= 6.1.1, < 7)
+
 PATH
   remote: .
   specs:
@@ -184,10 +192,6 @@ GEM
       rubocop (~> 1.44)
     rubocop-sorbet (0.7.0)
       rubocop (>= 0.90.0)
-    ruby-lsp (0.4.3)
-      language_server-protocol (~> 3.17.0)
-      sorbet-runtime
-      syntax_tree (>= 6.1.1, < 7)
     ruby-progressbar (1.13.0)
     sorbet (0.5.10736)
       sorbet-static (= 0.5.10736)
@@ -243,6 +247,7 @@ DEPENDENCIES
   rubocop-rake (~> 0.6.0)
   rubocop-shopify (~> 2.12)
   rubocop-sorbet (~> 0.7)
+  ruby-lsp!
   sorbet-static-and-runtime
   sqlite3
   tapioca (~> 0.11)

app/controllers/rails_ruby_lsp/models_controller.rb

@@ -0,0 +1,23 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RailsRubyLsp
+  class ModelsController < ApplicationController
+    extend T::Sig
+
+    sig { returns(T.untyped) }
+    def show
+      const = Object.const_get(params[:id]) # rubocop:disable Sorbet/ConstantsFromStrings
+
+      if const < ActiveRecord::Base
+        render(json: {
+          columns: const.columns.map { |column| [column.name, column.type] },
+        })
+      else
+        head(:not_found)
+      end
+    rescue NameError
+      head(:not_found)
+    end
+  end
+end

config/routes.rb

@@ -2,4 +2,5 @@
 # frozen_string_literal: true
 
 RailsRubyLsp::Engine.routes.draw do
+  resources :models, only: [:show]
 end

lib/rails_ruby_lsp/engine.rb

@@ -7,5 +7,21 @@
 module RailsRubyLsp
   class Engine < ::Rails::Engine
     isolate_namespace RailsRubyLsp
+
+    initializer "rails_ruby_lsp.routes" do
+      config.after_initialize do |app|
+        if Rails.env.development?
+          app.routes.prepend do
+            T.bind(self, ActionDispatch::Routing::Mapper)
+            mount(RailsRubyLsp::Engine => "/rails_ruby_lsp")
+          end
+        end
+
+        host = ENV.fetch("HOST") { "localhost" }
+        port = ENV.fetch("PORT") { "3000" }
+
+        File.write("#{Rails.root}/tmp/app_uri.txt", "http://#{host}:#{port}")
+      end
+    end
   end
 end

lib/ruby_lsp/extension.rb

@@ -0,0 +1,21 @@
+# typed: strict
+# frozen_string_literal: true
+
+require_relative "rails_client"
+require_relative "hover"
+
+module RailsRubyLsp
+  module RubyLsp
+    class Extension < ::RubyLsp::Extensions::Base
+      class << self
+        extend T::Sig
+
+        sig { override.void }
+        def activate
+          # Must be the last statement in activate since it raises to display a notification for the user
+          RailsRubyLsp::RailsClient.instance.check_if_server_is_running!
+        end
+      end
+    end
+  end
+end

lib/ruby_lsp/hover.rb

@@ -0,0 +1,25 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RailsRubyLsp
+  class Hover < ::RubyLsp::Extensions::Hover
+    class << self
+      extend T::Sig
+
+      sig { override.params(target: SyntaxTree::Node).returns(T.nilable(String)) }
+      def run(target)
+        case target
+        when SyntaxTree::Const
+          model = RailsClient.instance.model(target.value)
+          return if model.nil?
+
+          schema_file = File.join(RailsClient.instance.root, "db", "schema.rb")
+          content = +""
+          content << "[Schema](file://#{schema_file})\n\n" if File.exist?(schema_file)
+          content << model[:columns].map { |name, type| "**#{name}** | #{type}\n" }.join("\n")
+          content
+        end
+      end
+    end
+  end
+end

lib/ruby_lsp/rails_client.rb

@@ -0,0 +1,64 @@
+# typed: strict
+# frozen_string_literal: true
+
+require "singleton"
+require "net/http"
+
+module RailsRubyLsp
+  class RailsClient
+    class ServerNotRunningError < StandardError; end
+
+    extend T::Sig
+    include Singleton
+
+    SERVER_NOT_RUNNING_MESSAGE = "Rails server is not running. " \
+      "To get Rails features in the editor, boot the Rails server and restart the Ruby LSP"
+
+    sig { returns(String) }
+    attr_reader :root
+
+    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
+
+      @uri = T.let("#{base_uri}/rails_ruby_lsp", String)
+    end
+
+    sig { params(name: String).returns(T.nilable(T::Hash[Symbol, T.untyped])) }
+    def model(name)
+      response = request("models/#{name}")
+      return unless response.code == "200"
+
+      JSON.parse(response.body.chomp, symbolize_names: true)
+    rescue Errno::ECONNREFUSED
+      raise ServerNotRunningError, SERVER_NOT_RUNNING_MESSAGE
+    end
+
+    sig { void }
+    def check_if_server_is_running!
+      # Check if the Rails server is running. Warn the user to boot it for Rails features
+      pid_file = ENV.fetch("PIDFILE") { File.join(@root, "tmp", "pids", "server.pid") }
+
+      # If the PID file doesn't exist, then the server hasn't been booted
+      raise ServerNotRunningError, SERVER_NOT_RUNNING_MESSAGE unless File.exist?(pid_file)
+
+      pid = File.read(pid_file).to_i
+
+      begin
+        # Issuing an EXIT signal to an existing process actually doesn't make the server shutdown. But if this
+        # call succeeds, then the server is running. If the PID doesn't exist, Errno::ESRCH is raised
+        Process.kill(T.must(Signal.list["EXIT"]), pid)
+      rescue Errno::ESRCH
+        raise ServerNotRunningError, SERVER_NOT_RUNNING_MESSAGE
+      end
+    end
+
+    private
+
+    sig { params(path: String).returns(Net::HTTPResponse) }
+    def request(path)
+      Net::HTTP.get_response(URI("#{@uri}/#{path}"))
+    end
+  end
+end

sorbet/config

@@ -2,3 +2,4 @@
 .
 --ignore=tmp/
 --ignore=vendor/
+--ignore=test/dummy/db