MS Edge 18 error

Error unsupported regexp flag "n": /[0-9]/undefined 
    node_modules/parsimmon/build/parsimmon.umd.min.js:1:6716 Anonymous function
    node_modules/parsimmon/build/parsimmon.umd.min.js:1:6560 K
    node_modules/parsimmon/build/parsimmon.umd.min.js:1:11055 Anonymous function
    node_modules/parsimmon/build/parsimmon.umd.min.js:1:348 r
    node_modules/parsimmon/build/parsimmon.umd.min.js:1:407 Anonymous function
    node_modules/parsimmon/build/parsimmon.umd.min.js:1:199 Anonymous function
    node_modules/parsimmon/build/parsimmon.umd.min.js:1 Anonymous function
    webpack/bootstrap:25:3 __webpack_require__
    https://mywebsite.com/static/js/main.abc.js:1:123 Anonymous function
    webpack/bootstrap:25:3 __webpack_require__

Seeing the above a few times in my error tracker for Windows 10 devices running Edge 16 and Edge 18 (very old, non-chromium builds of the Edge browser).

Running the latest parsimmon at 1.15.0. We just recently upgraded from 1.12.0 and I hadn’t noticed these errors previously, if that’s helpful.

The error message is a bit odd, but my guess is that RegExp on these versions of Edge don’t support flags very well. It looks to me after reading the source for parsimmon that the regexp is literally presenting as the string "/[0-9]/undefined" when flags converts it to a string:

https://github.com/jneen/parsimmon/blob/cb77d09f900bb292389f0cf4870126bb5aa8b8d9/src/parsimmon.js#L696-L699

I tried to see if I could install that version on my Windows 10 machine, but I guess Microsoft has made that difficult to do side-by-side with the new Edge, so I wasn’t able to finish that try.

I mostly only bring this up because your README claims to support IE7+. I think this case would be not too hard to detect, if you’re willing to test it and support these old Edge versions.

[wavebeem]

Maybe you could even just add some kind of value logging to the internal flags function, like call stack and value of the re argument or something.

[wavebeem]

It seems literally impossible to find a way to install this ancient version of Edge, I can’t find an installer anywhere… 😬

Yeah this is what I was worried about. For now, I would suggest you fork Parsimmon and try out writing a patch yourself, and deploying it to your own app. Then watch those crash reports and tell me what’s up. Additionally, if you could add any kind of logging to Edge about the value of "" + /[0-9]/ that would be helpful.

If we can get to a high level of confidence about exactly what’s happening, I would welcome a patch, but for now I’d like more information.