Possible bug regarding dayjs.locale() usage

[denchen]

I want to have weekStart be 1 (start on Monday instead of Sunday), so my understanding is that we're supposed to use dayjs.locale() to override. So something like:

import dayjs from 'dayjs';
import en from 'dayjs/locale/en';

dayjs.locale({
  ...en,
  weekStart: 1
});

However, if I do this, then some functions break, such as dayjs().format('ll'), which gives me TypeError: Cannot read property 'replace' of undefined. Although dayjs().format('LL') does work.

I got around the problem by including formats in the locale info:

import dayjs from 'dayjs';
import en from 'dayjs/locale/en';

dayjs.locale({
  ...en,
  weekStart: 1,
  formats: {
    LT: 'h:mm A',
    LTS: 'h:mm:ss A',
    L: 'MM/DD/YYYY',
    LL: 'MMMM D, YYYY',
    LLL: 'MMMM D, YYYY h:mm A',
    LLLL: 'dddd, MMMM D, YYYY h:mm A'
  }
});

So my question is, am I supposed to include formats when overriding locale? Should I have to include other keys as well? Or is this a bug?

Information

• Day.js Version: 1.8.18
• OS: macOS Catalina 0.15.2
• Browser: Chrome 79.0.3945.88
• Time zone: GMT-07:00 PST (Pacific Daylight Time)

[iamkun]

You can try #766 UpdateLocale plugin in our latest release.

dayjs.updateLocale('en', {
  weekStart: 6
})