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


Thanks shyouhei for your pointing out. 

I imagine another Rexexp option, say `//I`, which is almost the same as `//i` except for never-applying SpecialCasing mapping. 
This change extends Unicode matching indeed but does not introduce incompatibilities, IMHO.
A difficulty is the implementation is on the upstream library and cruby is just a user. 

----------------------------------------
Bug #13671: Regexp with lookbehind and case-insensitivity raises RegexpError only on strings with certain characters
https://bugs.ruby-lang.org/issues/13671#change-73731

* 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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