From 04a0632a1c02425c576e1ad9d718109ddd7642eb Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Sun, 7 Jan 2024 23:39:57 +0900
Subject: [PATCH] - Fix an error when using heredoc with non-word delimiters
 (#987)

I've found #986 regression in the following RuboCop CI matrix:
https://github.com/rubocop/rubocop/actions/runs/7437077900/job/20234293932?pr=12598

So, #986 was not a sufficient fix. This PR fixes an error when using heredoc with non-word delimiters:

```ruby
<<~'+'
  foo
+
```

The following repro test have been newly added:

```console
$ bundle exec ruby -Itest test/test_lexer.rb
(snip)

  1) Error:
TestLexer#test_heredoc_plus_character:
RegexpError: target of repeat operator is not specified: /+\z/
    /Users/koic/src/github.com/whitequark/parser/lib/parser/lexer/literal.rb:250:in `delimiter?'
    /Users/koic/src/github.com/whitequark/parser/lib/parser/lexer/literal.rb:138:in `nest_and_try_closing'
    /Users/koic/src/github.com/whitequark/parser/lib/parser/lexer-strings.rb:4165:in `advance'
    /Users/koic/src/github.com/whitequark/parser/lib/parser/lexer-F1.rb:11369:in `advance'
    test/test_lexer.rb:81:in `assert_scanned'
    test/test_lexer.rb:1001:in `test_heredoc_plus_character'
```
---
 lib/parser/lexer/literal.rb |  2 +-
 test/test_lexer.rb          | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/lib/parser/lexer/literal.rb b/lib/parser/lexer/literal.rb
index b477a244f..ea32d750e 100644
--- a/lib/parser/lexer/literal.rb
+++ b/lib/parser/lexer/literal.rb
@@ -247,7 +247,7 @@ def delimiter?(delimiter)
         # E
         # because there are not enough leading spaces in the closing delimiter.
         delimiter.end_with?(@end_delim) &&
-          delimiter.sub(/#{@end_delim}\z/, '').bytes.all? { |c| c == SPACE }
+          delimiter.sub(/#{Regexp.escape(@end_delim)}\z/, '').bytes.all? { |c| c == SPACE }
       elsif @indent
         @end_delim == delimiter.lstrip
       else
diff --git a/test/test_lexer.rb b/test/test_lexer.rb
index cd3fc4dff..59541d1c2 100644
--- a/test/test_lexer.rb
+++ b/test/test_lexer.rb
@@ -997,6 +997,16 @@ def test_heredoc_one_character
                    :tNL,             nil,        [7, 8])
   end
 
+  def test_heredoc_plus_character
+    assert_scanned("a = <<'+'\nABCDEF\n+\n",
+                   :tIDENTIFIER,     "a",        [0, 1],
+                   :tEQL,            "=",        [2, 3],
+                   :tSTRING_BEG,     "<<\'",     [4, 9],
+                   :tSTRING_CONTENT, "ABCDEF\n", [10, 17],
+                   :tSTRING_END,     "+",        [17, 18],
+                   :tNL,             nil,        [9, 10])
+  end
+
   def test_heredoc_cr
     assert_scanned("a = <<E\r\r\nABCDEF\r\r\nE\r\r\r\n",
                    :tIDENTIFIER,     "a",          [0, 1],