I would expect this to not parse. Stepping through the code I see that parse of 'MMM'

'J-2' with 'MMM-d' return a date. about date-fns HOT 1 OPEN

michaeltford commented on June 1, 2024

'J-2' with 'MMM-d' return a date.

from date-fns.

Comments (1)

michaeltford commented on June 1, 2024

I created a workaround by creating StrictMonthParser that extends MonthParser and then setting it into the parsers.

This has two problems.
It changes the existing behavior and access a nested import.

A better solution (that I couldn't do without modifying the source to include 's' in formattingTokensRegExp). Is add a trailing 's' to the 'M' token types that only parsed strictly:

'Ms', 'MMs', 'MMMs', 'MMMs', 'MMMMs',

Additionally, my requirements did not need other tokens to be modified but this logic may apply to other parsers as well.

import { parsers } from "date-fns/parse/_lib/parsers/index.js";
parsers['M'] = new StrictMonthParser();

  parse(dateString: string, token: string, match: Match): ParseResult<number> {
    const valueCallback = (value: number) => value - 1

    switch (token) {
      // 1, 2, ..., 12
      case 'M':
        return mapValue(
          parseNumericPattern(numericPatterns.month, dateString),
          valueCallback
        )
      // 01, 02, ..., 12
      case 'MM':
        return mapValue(parseNDigits(2, dateString), valueCallback)
      // 1st, 2nd, ..., 12th
      case 'Mo':
        return mapValue(
          match.ordinalNumber(dateString, {
            unit: 'month',
          }),
          valueCallback
        )
      // Jan, Feb, ..., Dec
      case 'MMM':
        return (
          match.month(dateString, {
            width: 'abbreviated',
            context: 'formatting',
          })
          //  ||
          // match.month(dateString, { width: 'narrow', context: 'formatting' })
        )
      // J, F, ..., D
      case 'MMMMM':
        return match.month(dateString, {
          width: 'narrow',
          context: 'formatting',
        })
      // January, February, ..., December
      case 'MMMM':
      default:
        return (
          match.month(dateString, {
            width: 'wide',
            context: 'formatting'
          })
          //  ||
          // match.month(dateString, {
          //   width: 'abbreviated',
          //   context: 'formatting',
          // }) ||
          // match.month(dateString, { width: 'narrow', context: 'formatting' })
        )
    }
  }

from date-fns.

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