I'm not even sure what to title this, but I extracted it from test262/harness/testIntl.js. The following is false for JSC but true for all other engines: ``` /(?:\w+-)+((\w){5,8})-\1/.test('de-gregory-gregory') ``` This was as far as I could manage to shrink the regex. (The backreference can be inlined and the nested group can be made a non-capturing group, but everything else seems needed?)
This works tho 🤔 ``` /(?:\w+-)+(\w{5,8})-\1/.test('de-gregory-gregory') ```
(In reply to Devin Rousso from comment #1) > This works tho 🤔 > > ``` > /(?:\w+-)+(\w{5,8})-\1/.test('de-gregory-gregory') > ``` Hence the title. :P
(In reply to Ross Kirsling from comment #0) > The following is false for JSC but true for all other engines: Same result in Safari 12.1. I wonder if it's the same issue as in https://bugs.webkit.org/show_bug.cgi?id=188407?
(In reply to Ross Kirsling from comment #2) > (In reply to Devin Rousso from comment #1) > > This works tho 🤔 > > > > ``` > > /(?:\w+-)+(\w{5,8})-\1/.test('de-gregory-gregory') > > ``` > > Hence the title. :P 🤦♂️
Alexey noticed that my shrunken regex in comment 0 succeeds with a `u` flag, but the original regex does not. If we unshrink just a bit, this fails: /(?:\w+-)+((\w){5,8})-((\w){5,8}-)*\1/u.test('de-gregory-gregory') ...which may suggest multiple issues at play. I also kept trying ways to further shrink/restrict the comment 0 regex and noticed that the following fails (with or without `u`): /^(?:aa~)+(?:a){2,3}~aa?a?a?$/.test('aa~aa~aaaa') ...so nested groups may not be necessary, but that (?:a){2,3} is really important. It needs to be a quantified group with a lower bound greater than 1 and an upper bound greater than the lower bound. (Presumably the bound restrictions are needed so that it doesn't get automatically simplified?)