From: gotoken@...
Date: 2018-08-27T05:44:44+00:00
Subject: [ruby-core:88669] [Ruby trunk Bug#13671] Regexp with lookbehind and case-insensitivity raises RegexpError only on strings with certain characters

Issue #13671 has been updated by gotoken (Kentaro Goto).


Thanks znz. The workaround is helpful. And I understood what was happened.
https://github.com/k-takata/Onigmo/issues/92#issuecomment-373981492 shows how some combinations of letters are variable length.

For example, `"ss"` and `"st"` are mapped `"��"` (`"\u00DF"`) and `"���"` (`"\uFB06"`).
Those combinations are listed in ftp://ftp.unicode.org/Public/UNIDATA/SpecialCasing.txt

By the way, this expansion by `//i` option looks over kill for me. 
I wish case sensitivity and SpecialCasing mapping were separated...

----------------------------------------
Bug #13671: Regexp with lookbehind and case-insensitivity raises RegexpError only on strings with certain characters
https://bugs.ruby-lang.org/issues/13671#change-73726

* Author: dschweisguth (Dave Schweisguth)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: 2.4.1
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
Here is a test program:

~~~ ruby
def test(description)
  begin
    yield
    puts "#{description} is OK"
  rescue RegexpError
    puts "#{description} raises RegexpError"
  end
end

test("ass, case-insensitive, special") { /(?<!ass)/i =~ '���' }
test("bss, case-insensitive, special") { /(?<!bss)/i =~ '���' }
test("as,  case-insensitive, special") { /(?<!as)/i  =~ '���' }
test("ss,  case-insensitive, special") { /(?<!ss)/i  =~ '���' }
test("ass, case-sensitive,   special") { /(?<!ass)/  =~ '���' }
test("ass, case-insensitive, regular") { /(?<!ass)/i =~ 'x' }

~~~

Running the test program with Ruby 2.4.1 (macOS) gives

~~~
ass, case-insensitive, special raises RegexpError
bss, case-insensitive, special raises RegexpError
as,  case-insensitive, special is OK
ss,  case-insensitive, special is OK
ass, case-sensitive,   special is OK
ass, case-insensitive, regular is OK

~~~

The RegexpError is "invalid pattern in look-behind: /(?<!ass)/i (RegexpError)"

Side note: in the real code in which I found this error I was able to work around the error by using (?i) after the lookbehind instead of //i.

Running the test program with Ruby 2.3.4 does not report any RegexpErrors.

I think this is a regression, although I might be wrong and it might be saving me from an incorrect result with certain strings.

---Files--------------------------------
test.rb (531 Bytes)


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