2 years of Ruby LSP

This talk goes over the 2 years of development of the Ruby LSP. It starts showcasing some of its features, the current state of the internals and then goes into some of the future plans for the project.

1. Vinicius Stock 2 years of the Ruby LSP Current state and future
2. Vinicius Stock Sta ff dev @ Ruby DX team Shopify X: @vinistock GitHub: @vinistock https://vinistock.com
3. What is the Ruby LSP?
4. Ruby LSP https://github.com/Shopify/vscode-ruby-lsp https://github.com/Shopify/ruby-lsp https://code.visualstudio.com/docs/languages/ruby A language server for Ruby made in Ruby
5. Definition, hover and completion
6. Code lens
7. Formatting, diagnostics and quick fixes
8. Dependencies view
9. What is a language server?
10. It's a separate process that serves features for editors
11. require "open3" stdin, stderr, stdout, wait_thr = Open3.popen3("ruby-lsp")
12. require "open3" stdin, stderr, stdout, wait_thr = Open3.popen3("ruby-lsp") # Uses stdin to send requests # Uses stdout to receive responses
13. require "open3" stdin, stderr, stdout, wait_thr = Open3.popen3("ruby-lsp") # Uses stdin to send requests # Uses stdout to receive responses # Communication happens using JSON
14. require "open3" stdin, stderr, stdout, wait_thr = Open3.popen3("ruby-lsp") # Uses stdin to send requests # Uses stdout to receive responses # Communication happens using JSON # Prints all stderr to the editor's output
15. Notifications Requests No response expected Response expected
16. EDITOR SERVER STDOUT STDIN textDocument/didOpen class Foo end textDocument/foldingRange textDocument/foldingRange textDocument/didChange class Foo def bar end end textDocument/foldingRange textDocument/foldingRange
17. Open or edit fi le De fi nition, references, rename Notify the server Automatic Manual Trigger automatic requests Trigger desired request
18. What's the advantage of language servers?
19. Vim Ruby plugin Sublime VS Code Emacs Ruby plugin Ruby plugin Ruby plugin Go plugin Go plugin Go plugin Go plugin Rust plugin Rust plugin Rust plugin Rust plugin
20. Vim Ruby LSP Sublime VS Code Emacs
21. How does the Ruby LSP understands code? Analyzing Ruby code
22. class Foo def bar end end { "textDocument": { "uri": "file: / / / foo.rb" } } [ { "startLine": 1, "endLine": 1, "kind": "region" } ]
23. AST Ruby code Response Parse Analysis Prism Visitor + Observer
24. Turning a Ruby code string into a useful object Parsing
25. class Foo def bar "Hey!" end end CLASS CONST (Foo) DEF (bar) STRING (Hey!)
26. Double dispatch visitor Allows traversing the AST with dedicated logic in an organized way
27. class Visitor def visit(node) node.accept(self) end end
28. class ClassNode def accept(visitor) visitor.visit_class_node(self) end end
29. class Visitor def visit_child_nodes(node) node.child_nodes.each do |child| visit(child) end end alias_method :visit_class_node, :visit_child_nodes alias_method :visit_module_node, :visit_child_nodes end
30. class MyVisitor < Prism : : Visitor def visit_class_node(node) puts "Hi, # { node.constant_path.full_name}" super end end
31. ast = Prism.parse_file("foo.rb").value visitor = MyVisitor.new visitor.visit(ast) # = > Hi, Foo
32. Observer Allows us to have multiple concerns triggered by the same events
33. dispatcher = Dispatcher.new dispatcher.on(:certain_event) do do_something! end
34. dispatcher = Dispatcher.new dispatcher.on(:certain_event) do do_something! end dispatcher.fire(:certain_event)
35. Ruby LSP uses a mix of both
36. The dispatcher is a visitor that fi res events for each node encountered in the AST
37. class Dispatcher < Prism : : Visitor def initialize @listeners = Hash.new do |h, k| h[k] = [] end end end
38. class Dispatcher < Prism : : Visitor def register(listener, *events) events.each do |e| @listeners[e] < < listener end end end
39. class Dispatcher < Prism : : Visitor def visit_class_node(node) @listeners[:on_class_node].each do |l| l.on_class_node(node) end super end end
40. All features are listeners that respond to speci fi c nodes being found in the AST
41. class Foo def bar "Hey!" end end
42. CLASS CONST (Foo) DEF (bar) STRING (Hey!) Listener 1 classes Dispatcher Listener 2 classes and methods Event Event Event
43. The Ruby LSP computes 5 distinct features in a single traversal of the AST
44. Traversing our ~270 line implementation of folding range once produces ~1000 visits
45. Implementing folding range Creating a listener to fold class declarations
46. class FoldingRange def initialize(dispatcher) dispatcher.register( self, :on_class_node ) @ranges = [] end end
47. class FoldingRange def on_class_node(node) loc = node.location @ranges < < { startLine: loc.start_line, endLine: loc.end_line, kind: "region" } end end
48. ast = Prism.parse_file("foo.rb").value
49. ast = Prism.parse_file("foo.rb").value dispatcher = Prism : : Dispatcher.new
50. ast = Prism.parse_file("foo.rb").value dispatcher = Prism : : Dispatcher.new listener = FoldingRange.new(dispatcher)
51. ast = Prism.parse_file("foo.rb").value dispatcher = Prism : : Dispatcher.new listener = FoldingRange.new(dispatcher) dispatcher.dispatch(ast)
52. ast = Prism.parse_file("foo.rb").value dispatcher = Prism : : Dispatcher.new listener = FoldingRange.new(dispatcher) dispatcher.dispatch(ast) # The listener's response will be populated # with all ranges
53. How would we compute many features during the same traversal of the AST?
54. ast = Prism.parse_file("foo.rb").value dispatcher = Prism : : Dispatcher.new folding_range = FoldingRange.new(dispatcher) document_symbol = DocumentSymbol.new(dispatcher) semantic_highlighting = SemanticHighlighting.new(dispatcher) dispatcher.dispatch(ast)
55. And we concluded our folding range implementation 🎉
56. What's next for the Ruby LSP? • Making Ruby activation more robust and improving error handling • Full method support for de fi nition, hover and completion and signature help • Refactors
57. • Rename • Occurrences • Show type hierarchy • More debugging features What's next for the Ruby LSP?
58. Great DX comes from good integration Future bets
59. The Ruby tooling ecosystem is fragmented Future bets
60. Many formatters, linters, type checkers, test frameworks, documentation tools, version managers, web frameworks... Future bets
61. We want to provide a one click set up experience Future bets
62. You get features based on the tools your application uses without having to con fi gure anything Future bets
63. Addons • A way for other gems to enhance Ruby LSP features • The Ruby LSP should automatically detect which addon to load based on your project's dependencies • Rails addon: https://github.com/Shopify/ruby-lsp-rails
64. Challenges with addons • How to detect which addons to install based on the dependency? • Should the addons be embedded in the gems they are related to? Or should they be separate gems? • How do we allow for con fi guration that is editor agnostic? A `~/.ruby-lsprc` fi le?
65. We need your help
66. We can de fi nitely have a one-click set up experience
67. Thank you!
68. • https://github.com/Shopify/vscode-ruby-lsp • https://github.com/Shopify/ruby-lsp • https://github.com/Shopify/ruby-lsp-rails • Font: https://github.com/microsoft/cascadia-code • https://microsoft.github.io/language-server-protocol/speci fi cations/lsp/ 3.17/speci fi cation/ • All videos/screenshots made with VS Code References