Use RubyVM::InstructionSequence.compile instead of open3

Author: mtsmfm

lib/language_server/linter/ruby_wc.rb

@@ -1,4 +1,4 @@
-require "open3"
+require "stringio"
 
 module LanguageServer
   module Linter
@@ -26,12 +26,55 @@ def initialize(source)
       end
 
       def call
-        _, err, _ = Open3.capture3("ruby -wc", stdin_data: @source)
-
-        err.scan(/.+:(\d+):\s*(.+?)[,:]\s(.+)/).map do |line_num, type,  message|
+        error_message.scan(/.+:(\d+):\s*(.+?)[,:]\s(.+)/).map do |line_num, type,  message|
           Error.new(line_num: line_num.to_i - 1, message: message, type: type)
         end
       end
+
+      private
+
+      # Since Ruby 2.4, syntax error information is outputted to Exception#message instead of stderr
+      if begin; stderr = $stderr; $stderr = StringIO.new; RubyVM::InstructionSequence.compile('='); rescue SyntaxError => e; e.message != 'compile error'; ensure; $stderr = stderr; end
+        def error_message
+          with_verbose do
+            begin
+              capture_stderr { RubyVM::InstructionSequence.compile(@source) }
+            rescue SyntaxError => e
+              e.message
+            end
+          end
+        end
+      else
+        def error_message
+          with_verbose do
+            capture_stderr do
+              begin
+                RubyVM::InstructionSequence.compile(@source)
+              rescue SyntaxError
+              end
+            end
+          end
+        end
+      end
+
+      def with_verbose
+        origin = $VERBOSE
+        $VERBOSE = true
+        yield
+      ensure
+        $VERBOSE = origin
+      end
+
+      def capture_stderr
+        origin = $stderr
+        $stderr = StringIO.new
+
+        yield
+
+        $stderr.string
+      ensure
+        $stderr = origin
+      end
     end
   end
 end