RegExp issue with very long attributes

[rossj]

I've ran into a parsing issue with some very long XML attributes. For example, the following will raise a RangeError: Maximum call stack size exceeded while running the Attribute regex:

parseXml(`<a b="${'a'.repeat(9000000)}"/>`);

I was able to avoid the error by slightly relaxing the attribute value parts of the Attribute regex as follows:

[^<&"] | ${exports.Reference} => [^<"]

but this change causes 4 tests to fail that are expecting exceptions from various bad & uses in attribute values.

Perhaps the regexes could be kept strict while avoiding the call stack exception, or perhaps a 2-phase approach could be used where the attribute value is checked for invalid references after being parsed from the overall tag.

[rgrove]

Thanks for reporting this! I haven't investigated the problem or your proposed solution yet, but I'll try to take a look soon. This work will probably align well with the larger investigation I want to do (prompted by your earlier issue #9) into the possibility of relying less on regexes, or at least hardening them to be less fragile in cases like this.