Add support for new absence operator (#33)

README.md

@@ -329,6 +329,7 @@ _Note that not all of these are available in all versions of Ruby_
 | &emsp;&emsp;_Lookbehind_              | `(?<=abc)`                                              | &#x2713; |
 | &emsp;&emsp;_Negative Lookbehind_     | `(?<!abc)`                                              | &#x2713; |
 | &emsp;&nbsp;_**Atomic**_              | `(?>abc)`                                               | &#x2713; |
+| &emsp;&nbsp;_**Absence**_             | `(?~abc)`                                               | &#x2713; |
 | &emsp;&nbsp;_**Back-references**_     |                                                         | &#x22f1; |
 | &emsp;&emsp;_Named_                   | `\k<name>`                                              | &#x2713; |
 | &emsp;&emsp;_Nest Level_              | `\k<n-1>`                                               | &#x2713; |

lib/regexp_parser/expression/classes/group.rb

@@ -31,6 +31,7 @@ class Atomic    < Group::Base; end
     class Capture   < Group::Base; end
     class Passive   < Group::Base; end
     class Options   < Group::Base; end
+    class Absence   < Group::Base; end
 
     class Named     < Group::Capture
       attr_reader :name

lib/regexp_parser/lexer.rb

@@ -4,7 +4,7 @@
 # given syntax flavor.
 module Regexp::Lexer
 
-  OPENING_TOKENS = [:capture, :options, :passive, :atomic, :named,
+  OPENING_TOKENS = [:capture, :options, :passive, :atomic, :named, :absence,
                     :lookahead, :nlookahead, :lookbehind, :nlookbehind
                    ].freeze
 

lib/regexp_parser/parser.rb

@@ -470,6 +470,8 @@ def self.open_group(token)
       exp = Group::Named.new(token)
     when :capture
       exp = Group::Capture.new(token)
+    when :absence
+      exp = Group::Absence.new(token)
 
     when :lookahead
       exp = Assertion::Lookahead.new(token)

lib/regexp_parser/scanner/scanner.rl

@@ -82,6 +82,7 @@
 
   group_atomic          = '?>';
   group_passive         = '?:';
+  group_absence         = '?~';
 
   assertion_lookahead   = '?=';
   assertion_nlookahead  = '?!';
@@ -107,7 +108,7 @@
   group_number_ref      = group_ref . (('<' . group_number . group_level? '>') |
                                        ("'" . group_number . group_level? "'"));
 
-  group_type            = group_atomic | group_passive | group_named;
+  group_type            = group_atomic | group_passive | group_absence | group_named;
 
 
   assertion_type        = assertion_lookahead  | assertion_nlookahead |
@@ -573,6 +574,7 @@
     # Groups
     #   (?:subexp)          passive (non-captured) group
     #   (?>subexp)          atomic group, don't backtrack in subexp.
+    #   (?~subexp)          absence group, matches anything that is not subexp
     #   (?<name>subexp)     named group
     #   (?'name'subexp)     named group (single quoted version)
     #   (subexp)            captured group
@@ -581,6 +583,7 @@
       case text = text(data, ts, te).first
       when '(?:';  emit(:group, :passive,      text, ts, te)
       when '(?>';  emit(:group, :atomic,       text, ts, te)
+      when '(?~';  emit(:group, :absence,      text, ts, te)
 
       when /^\(\?<(\w*)>/
         empty_name_error(:group, 'named group (ab)') if $1.empty?

lib/regexp_parser/syntax/ruby/2.4.1.rb

@@ -6,6 +6,8 @@ module Ruby
     class V241 < Regexp::Syntax::Ruby::V240
       def initialize
         super
+
+        implements :group, Group::Absence
       end
     end
 

lib/regexp_parser/syntax/tokens/group.rb

@@ -13,6 +13,8 @@ module Group
       All = Group::Extended + Group::Named + Group::Atomic +
             Group::Passive + Group::Comment
 
+      Absence = [:absence]
+
       Type = :group
     end
 

test/parser/test_groups.rb

@@ -106,4 +106,17 @@ def test_parse_comment
     end
   end
 
+  if RUBY_VERSION >= '2.4.1'
+    def test_parse_absence_group
+      t = RP.parse('a(?~b)c(?~d)e')
+
+      [1,3].each do |i|
+        assert t.expressions[i].is_a?(Group::Absence),
+               "Expected absence group, but got #{t.expressions[i].class.name}"
+
+        assert_equal :group,   t.expressions[i].type
+        assert_equal :absence, t.expressions[i].token
+      end
+    end
+  end
 end

test/scanner/test_groups.rb

@@ -55,6 +55,13 @@ class ScannerGroups < Test::Unit::TestCase
     })
   end
 
+  if RUBY_VERSION >= '2.4.1'
+    tests.merge!({
+      # New absence operator
+      '(?~abc)'       => [0, :group,     :absence,      '(?~',        0, 3],
+    })
+  end
+
   tests.each_with_index do |(pattern, (index, type, token, text, ts, te)), count|
     define_method "test_scanner_#{type}_#{token}_#{count}" do
       tokens = RS.scan(pattern)

test/warnings.yml

@@ -1,6 +1,6 @@
 ---
 # Unused variable emitted by ragel
-- "lib/regexp_parser/scanner.rb:1674: warning:
+- "lib/regexp_parser/scanner.rb:1675: warning:
   assigned but unused variable - testEof"
 
 # Unavoidable duplicated character range tests
@@ -10,7 +10,7 @@
   character class has duplicated range: /[a[b[^c]]]/"
 
 # Warnings generated only under 1.9.3
-- "lib/regexp_parser/scanner.rb:1675:
+- "lib/regexp_parser/scanner.rb:1676:
   warning: assigned but unused variable - _acts"
-- "lib/regexp_parser/scanner.rb:1675:
+- "lib/regexp_parser/scanner.rb:1676:
   warning: assigned but unused variable - _nacts"