Catch \k<0>

ammar · Feb 28, 2023 · f8884f7 · f8884f7
1 parent cee8b82
commit f8884f7
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Showing 3 changed files with 26 additions and 28 deletions.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -48,7 +48,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   * e.g. in `/(a)(?(1)b|c(?#hello)d)e/`, the 2nd conditional branch included "e"
 - fixed quantifiers after comment groups being mis-assigned to that group
   * e.g. in `/a(?#foo){3}/` (matches 'aaa')
-- fixed scanner accepting unmatched closing parentheses ')'
+- fixed Scanner accepting two cases of invalid Regexp syntax
+  * unmatched closing parentheses (`)`) and k-backrefs with number 0 (`\k<0>`)
   * these are a `SyntaxError` in Ruby, so could only be passed as a String
   * they now raise a `Regexp::Scanner::ScannerError`
 - fixed some scanner errors not inheriting from `Regexp::Scanner::ScannerError`

diff --git a/lib/regexp_parser/scanner/scanner.rl b/lib/regexp_parser/scanner/scanner.rl
@@ -83,10 +83,9 @@
   # try to treat every other group head as options group, like Ruby
   group_options         = '?' . ( [^!#'():<=>~]+ . ':'? ) ?;
 
-  group_ref             = [gk];
   group_name_id_ab      = ([^!0-9\->] | utf8_multibyte) . ([^>] | utf8_multibyte)*;
   group_name_id_sq      = ([^0-9\-']  | utf8_multibyte) . ([^'] | utf8_multibyte)*;
-  group_number          = '-'? . [1-9] . [0-9]*;
+  group_number          = '-'? . [0-9]+;
   group_level           = [+\-] . [0-9]+;
 
   group_name            = ('<' . group_name_id_ab? . '>') |
@@ -95,15 +94,11 @@
 
   group_named           = ('?' . group_name );
 
-  group_name_backref    = 'k' . (('<' . group_name_id_ab? . group_level? '>') |
-                                 ("'" . group_name_id_sq? . group_level? "'"));
-  group_name_call       = 'g' . (('<' . group_name_id_ab? . group_level? '>') |
-                                 ("'" . group_name_id_sq? . group_level? "'"));
+  group_ref_body        = (('<' . (group_name_id_ab? | group_number) . group_level? '>') |
+                           ("'" . (group_name_id_sq? | group_number) . group_level? "'"));
 
-  group_number_backref  = 'k' . (('<' . group_number . group_level? '>') |
-                                 ("'" . group_number . group_level? "'"));
-  group_number_call     = 'g' . (('<' . ((group_number . group_level?) | '0') '>') |
-                                 ("'" . ((group_number . group_level?) | '0') "'"));
+  group_ref             = 'k' . group_ref_body;
+  group_call            = 'g' . group_ref_body;
 
   group_type            = group_atomic | group_passive | group_absence | group_named;
 
@@ -548,35 +543,35 @@
 
     # Group backreference, named and numbered
     # ------------------------------------------------------------------------
-    backslash . (group_name_backref | group_number_backref) > (backslashed, 4) {
+    backslash . (group_ref) > (backslashed, 4) {
       case text = copy(data, ts, te)
-      when /^\\k(<>|'')/
-        raise ValidationError.for(:backref, 'backreference', 'ref ID is empty')
-      when /^\\k(.)[^\p{digit}\-][^+\-]*\D$/
+      when /^\\k(.)[^0-9\-][^+\-]*['>]$/
         emit(:backref, $1 == '<' ? :name_ref_ab : :name_ref_sq, text)
-      when /^\\k(.)\d+\D$/
+      when /^\\k(.)[1-9]\d*['>]$/
         emit(:backref, $1 == '<' ? :number_ref_ab : :number_ref_sq, text)
-      when /^\\k(.)-\d+\D$/
+      when /^\\k(.)-[1-9]\d*['>]$/
         emit(:backref, $1 == '<' ? :number_rel_ref_ab : :number_rel_ref_sq, text)
-      when /^\\k(.)[^\p{digit}\-].*[+\-]\d+\D$/
+      when /^\\k(.)[^0-9\-].*[+\-]\d+['>]$/
         emit(:backref, $1 == '<' ? :name_recursion_ref_ab : :name_recursion_ref_sq, text)
-      when /^\\k(.)-?\d+[+\-]\d+\D$/
+      when /^\\k(.)-?[1-9]\d*[+\-]\d+['>]$/
         emit(:backref, $1 == '<' ? :number_recursion_ref_ab : :number_recursion_ref_sq, text)
+      else
+        raise ValidationError.for(:backref, 'backreference', 'invalid ref ID')
       end
     };
 
     # Group call, named and numbered
     # ------------------------------------------------------------------------
-    backslash . (group_name_call | group_number_call) > (backslashed, 4) {
+    backslash . (group_call) > (backslashed, 4) {
       case text = copy(data, ts, te)
-      when /^\\g(<>|'')/
-        raise ValidationError.for(:backref, 'subexpression call', 'ref ID is empty')
-      when /^\\g(.)[^\p{digit}+\->][^+\-]*/
+      when /^\\g(.)[^0-9+\-].*['>]$/
         emit(:backref, $1 == '<' ? :name_call_ab : :name_call_sq, text)
-      when /^\\g(.)\d+\D$/
+      when /^\\g(.)\d+['>]$/
         emit(:backref, $1 == '<' ? :number_call_ab : :number_call_sq, text)
       when /^\\g(.)[+-]\d+/
         emit(:backref, $1 == '<' ? :number_rel_call_ab : :number_rel_call_sq, text)
+      else
+        raise ValidationError.for(:backref, 'subexpression call', 'invalid ref ID')
       end
     };
 

diff --git a/spec/scanner/errors_spec.rb b/spec/scanner/errors_spec.rb
@@ -62,10 +62,12 @@
   include_examples 'scan error', RS::InvalidGroupOption, 'invalid neg option', '(?-foo)'
   include_examples 'scan error', RS::InvalidGroupOption, 'invalid neg option', '(?-u)'
   include_examples 'scan error', RS::InvalidGroupOption, 'invalid neg option', '(?-mixu)'
-  include_examples 'scan error', RS::InvalidBackrefError, 'empty backref', '\k<>'
-  include_examples 'scan error', RS::InvalidBackrefError, 'empty backref', '\k\'\''
-  include_examples 'scan error', RS::InvalidBackrefError, 'empty refcall', '\g<>'
-  include_examples 'scan error', RS::InvalidBackrefError, 'empty refcall', '\g\'\''
+  include_examples 'scan error', RS::InvalidBackrefError, 'invalid backref', '\k<>'
+  include_examples 'scan error', RS::InvalidBackrefError, 'invalid backref', '\k\'\''
+  include_examples 'scan error', RS::InvalidBackrefError, 'invalid backref', '\k<0>'
+  include_examples 'scan error', RS::InvalidBackrefError, 'invalid backref', '\k\'0\''
+  include_examples 'scan error', RS::InvalidBackrefError, 'invalid refcall', '\g<>'
+  include_examples 'scan error', RS::InvalidBackrefError, 'invalid refcall', '\g\'\''
   include_examples 'scan error', RS::UnknownUnicodePropertyError, 'unknown property', '\p{foobar}'
   include_examples 'scan error', RS::UnknownPosixClassError, 'unknown POSIX class [::]', '[[::]]'
   include_examples 'scan error', RS::UnknownPosixClassError, 'unknown POSIX class [:^:]', '[[:^:]]'