lexer.rb: ignore dedented space

* ext/ripper/lib/ripper/lexer.rb (on_heredoc_dedent): replace an
  empty string content because of dedentation with :on_ignored_sp.
  an empty token makes the sorted order unstable.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59269 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/ripper/lib/ripper/lexer.rb

@@ -72,6 +72,11 @@ class Ripper
         if Elem === e and e.event == :on_tstring_content
           tok = e.tok.dup if w > 0 and /\A\s/ =~ e.tok
           if (n = dedent_string(e.tok, w)) > 0
+            if e.tok.empty?
+              e.tok = tok[0, n]
+              e.event = :on_ignored_sp
+              next
+            end
             ignored_sp << [i, Elem.new(e.pos.dup, :on_ignored_sp, tok[0, n])]
             e.pos[1] += n
           end

test/ripper/test_lexer.rb

@@ -32,4 +32,23 @@ class TestRipper::Lexer < Test::Unit::TestCase
     E
     assert_equal(str, Ripper.tokenize(str).join(""), bug)
   end
+
+  def test_embedded_expr_in_heredoc
+    src = <<~'E'
+    <<~B
+      #{1}
+    B
+    E
+    expect = %I[
+      on_heredoc_beg
+      on_nl
+      on_ignored_sp
+      on_embexpr_beg
+      on_int
+      on_embexpr_end
+      on_tstring_content
+      on_heredoc_end
+    ]
+    assert_equal expect, Ripper.lex(src).map {|e| e[1]}
+  end
 end