Validating regexp

[Larry Martell]

On Wed, Aug 9, 2017 at 6:13 AM, Peter Heitzer
<peter.heitzer at rz.uni-regensburg.de> wrote:
> Larry Martell <larry.martell at gmail.com> wrote:
>>On Tue, Aug 8, 2017 at 12:51 PM, Chris Angelico <rosuav at gmail.com> wrote:
>>> On Wed, Aug 9, 2017 at 2:37 AM, Larry Martell <larry.martell at gmail.com> wrote:
>>>> Anyone have any code or know of any packages for validating a regexp?
>>>>
>>>> I have an app that allows users to enter regexps for db searching.
>>>> When a user enters an invalid one (e.g. 'A|B|' is one I just saw) it
>>>> causes downstream issues. I'd like to flag it at entry time.
>>>
>>> re.compile()? Although I'm not sure that 'A|B|' is actually invalid.
>>> But re.compile("(") throws.
>
>>Yeah, it does not throw for 'A|B|' - but mysql chokes on it with empty
>>subexpression for regexp' I'd like to flag it before it gets to SQL.
>
> Then you need to do a real sql query with the regex and check if it throws.

Yes, that is what I ended up doing.