toMillis: Width formatting is not respected without a separator

[JAMSUPREME]

Bug Summary

Width formatting doesn't appear to be respected without a separator.

Versions

JSONata 1.8.5
Node v14.17.0

Detailed Information

Reference spec for width formatting: https://www.w3.org/TR/xpath-functions-31/#date-time-examples

At the moment, it appears the width formatting is not honored within $toMillis due to the way the regex is being generated. For an example input 201802, I should be able to specify a matcher [Y0001][M01] which will result in a parsed value of 2018/02/01. At the moment, the library incorrectly grabs too many characters due to the + regex so I end up with 20180/02/01

Suggested Fix

I attempted a fix but you can let me know whether or not it's reasonable: #545

Work-around

I made a little helper function to grab the fixed-width portions of year/month/date via substring and then reformat the string prior to sending it to toMillis:

const dateFunc = `
  $dateYMD := function($date) {( 
    $year := $substring($date, 0, 4);
    $month := $substring($date, 4, 2);
    $day := $substring($date, 6, 2);
    $year & '-' & $month & '-' & $day
  )};
`;

The library then functions as expected once the date string has been split via separators.

[JAMSUPREME]

Closing. Fixed via #545