[Help-smalltalk] [bug] (a RegexResults) at: n throws error if captured at n is empty string

[sergio]

Issue status update for 
http://smalltalk.gnu.org/node/835
Post a follow up: 
http://smalltalk.gnu.org/project/comments/add/835

Project:      GNU Smalltalk
Version:      <none>
Component:    Base classes
Category:     bug reports
Priority:     normal
Assigned to:  Unassigned
Reported by:  sergio
Updated by:   sergio
Status:       active

Small code will be best description:


   * !/usr/local/bin/gst -f


data := 'word1 "" word3'.

" next regex catches whatever is between quotes; 
  when there is something it works; when there is not - later 
  attempt to access matches at: 2 throws "

(data =~ '(\w+) "([^"]*)" (\w+)')
  ifMatched: [ :matches |  
    | w2 mm |
    Transcript 
      show: 'Matches size is: ', matches size asString ;  
      nl ;  
      flush.
    
    " w2 := matches at: 2.    // will throw "
    " mm := matches asArray.  // will throw as it internally calls at:
"
    
    " next cycle will throw on 2nd iteration: "
    1 to: matches size do: [ :n | 
      Transcript show: 'Matches at: ' , n asString , ' is: [' 
          , (matches at: n) , ']' ;  nl ;  flush ] ].

Output is:

$ ./test1 
Matches size is: 3
Matches at: 1 is: [word1]
Object: Interval new "<0x2aaaac9b7870>" error: Invalid index 1: index
out of range
SystemExceptions.IndexOutOfRange(Exception)>>signal (ExcHandling.st:254)
SystemExceptions.IndexOutOfRange class>>signalOn:withIndex:
(SysExcept.st:660)
Interval>>first (Interval.st:245)
Kernel.MatchingRegexResults>>at: (Regex.st:382)
optimized [] in UndefinedObject>>executeStatements (test1:21)
Kernel.MatchingRegexResults>>ifNotMatched:ifMatched: (Regex.st:322)
Kernel.MatchingRegexResults(RegexResults)>>ifMatched: (Regex.st:188)
UndefinedObject>>executeStatements (test1:7)

I believe it is regress, it worked for me in gst that was... some years
ago, perhaps in Debian 6. I can not say what version it was.