[ruby/yarp] Split out newline test

https://github.com/ruby/yarp/commit/eeb4f6cb9d

test/newline_test.rb

@@ -0,0 +1,77 @@
+# frozen_string_literal: true
+
+require "yarp_test_helper"
+
+class NewlineTest < Test::Unit::TestCase
+  class NewlineVisitor < YARP::Visitor
+    attr_reader :source, :newlines
+
+    def initialize(source)
+      @source = source
+      @newlines = []
+    end
+
+    def visit(node)
+      newlines << source.line(node.location.start_offset) if node&.newline?
+      super(node)
+    end
+  end
+
+  root = File.dirname(__dir__)
+  Dir["{lib,test}/**/*.rb", base: root].each do |relative|
+    filepath = File.join(root, relative)
+
+    define_method "test_newline_flags_#{relative}" do
+      source = File.read(filepath, binmode: true, external_encoding: Encoding::UTF_8)
+      expected = rubyvm_lines(source)
+
+      result = YARP.parse(source, relative)
+      assert_empty result.errors
+
+      result.mark_newlines
+      visitor = NewlineVisitor.new(result.source)
+      result.value.accept(visitor)
+      actual = visitor.newlines
+
+      if relative == "lib/yarp/serialize.rb"
+        # while (b = io.getbyte) >= 128 has 2 newline flags
+        expected.delete_at actual.index(62)
+      elsif relative == "lib/yarp/lex_compat.rb"
+        # extra flag for: dedent_next =\n  ((token.event: due to bytecode order
+        actual.delete(514)
+        # different line for: token =\n  case event: due to bytecode order
+        actual.delete(571)
+        expected.delete(572)
+        # extra flag for: lex_state =\n  if RIPPER: due to bytecode order
+        actual.delete(604)
+        # extra flag for: (token[2].start_with?("\#$") || token[2].start_with?("\#@"))
+        # unclear when ParenthesesNode should allow a second flag on the same line or not
+        actual.delete(731)
+      end
+
+      assert_equal expected, actual
+    end
+  end
+
+  private
+
+  def ignore_warnings
+    previous_verbosity = $VERBOSE
+    $VERBOSE = nil
+    yield
+  ensure
+    $VERBOSE = previous_verbosity
+  end
+
+  def rubyvm_lines(source)
+    queue = [ignore_warnings { RubyVM::InstructionSequence.compile(source) }]
+    lines = []
+
+    while iseq = queue.shift
+      lines.concat(iseq.trace_points.filter_map { |line, event| line if event == :line })
+      iseq.each_child { |insn| queue << insn unless insn.label.start_with?("ensure in ") }
+    end
+
+    lines.sort
+  end
+end