[wip] experimental typo checker

Gemfile

@@ -2,3 +2,5 @@ source 'https://rubygems.org'
 
 # Specify your gem's dependencies in language_server.gemspec
 gemspec
+
+gem 'did_you_mean', git: 'https://github.com/yuki24/did_you_mean', branch: 'static-typo-checker'

lib/language_server.rb

@@ -2,6 +2,7 @@
 require "language_server/logger"
 require "language_server/protocol"
 require "language_server/linter/ruby_wc"
+require "language_server/linter/did_you_mean"
 require "language_server/completion_provider/rcodetools"
 require "language_server/completion_provider/ad_hoc"
 require "language_server/definition_provider/ad_hoc"
@@ -94,7 +95,10 @@ def on(method, &callback)
     file_store.cache(uri, text)
     project.recalculate_result(uri)
 
-    diagnostics = Linter::RubyWC.new(text).call.map do |error|
+    diagnostics = [
+      Linter::RubyWC.new(text).call,
+      Linter::DidYouMean.new(text).call
+    ].flatten.map do |error|
       Protocol::Interface::Diagnostic.new(
         message: error.message,
         severity: error.warning? ? Protocol::Constant::DiagnosticSeverity::WARNING : Protocol::Constant::DiagnosticSeverity::ERROR,

lib/language_server/linter/did_you_mean.rb

@@ -0,0 +1,20 @@
+require "open3"
+require "language_server/linter/error"
+
+module LanguageServer
+  module Linter
+    class DidYouMean
+      def initialize(source)
+        @source = source
+      end
+
+      def call
+        out, _, _ = Open3.capture3("ruby -r bundler/setup -r did_you_mean/static", stdin_data: @source)
+
+        (JSON.parse(out, symbolize_names: true)[:undefined_names] || {}).values.flatten.map do |undefined_name:, symbol_type:, path:, lineno:, suggestions:|
+          Error.new(line_num: lineno - 1, message: "Undefined method #{undefined_name}. Did you mean? #{suggestions.join("\n")}", type: 'warning')
+        end
+      end
+    end
+  end
+end

lib/language_server/linter/error.rb

@@ -0,0 +1,23 @@
+require "open3"
+
+module LanguageServer
+  module Linter
+    class Error
+      attr_reader :line_num, :message, :type
+
+      def initialize(line_num:, message:, type:)
+        @line_num = line_num
+        @message = message
+        @type = type
+      end
+
+      def warning?
+        @type == "warning"
+      end
+
+      def ==(other)
+        line_num == other.line_num && message == other.message
+      end
+    end
+  end
+end

test/language_server/linter/did_you_mean_test.rb

@@ -0,0 +1,17 @@
+require 'test_helper'
+
+module LanguageServer::Linter
+  class DidYouMeanTest < Minitest::Test
+    def test_error
+      linter = DidYouMean.new(<<-EOS.strip_heredoc)
+        def hi
+          foo
+        end
+      EOS
+
+      assert {
+        linter.call == [Error.new(line_num: 1, message: "Undefined method foo. Did you mean? for", type: "warning")]
+      }
+    end
+  end
+end