Add ignored_sp event

* ext/ripper/lib/ripper/lexer.rb (Ripper::Lexer): add ignored_sp
  event which will be fired from Ripper::Lexer#on_heredoc_dedent
  method.  [ruby-core:91727] [Bug #15648]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@67200 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ext/ripper/lib/ripper/lexer.rb

@@ -83,6 +83,12 @@ class Ripper
 
     private
 
+    unless SCANNER_EVENT_TABLE.key?(:ignored_sp)
+      SCANNER_EVENT_TABLE[:ignored_sp] = 1
+      SCANNER_EVENTS << :ignored_sp
+      EVENTS << :ignored_sp
+    end
+
     def on_heredoc_dedent(v, w)
       ignored_sp = []
       heredoc = @buf.last

test/ripper/test_scanner_events.rb

@@ -888,6 +888,13 @@ class TestRipper::ScannerEvents < Test::Unit::TestCase
                  scan('ignored_nl', "1;\r\n")
   end
 
+  def test_ignored_sp
+    assert_equal [],
+                 scan('ignored_sp', "<<~EOS\nheredoc\nEOS")
+    assert_equal ["  "],
+                 scan('ignored_sp', "<<~EOS\n  heredoc\nEOS")
+  end
+
   def test___end__
     assert_equal [],
                  scan('__end__', "")