Cannot find module 'dayjs/plugin/timezone' in sub-module

[spsaucier-bakkt]

Describe the bug
Similar to #1135, getting Cannot find module 'dayjs/plugin/timezone' from 'node_modules/my-module' when importing my module from elsewhere and trying to run tests.

The plugin works properly within the code where it's used, but this issue appears when importing it as node_module.

Expected behavior
Able to import dayjs plugins and use them in code used as a sub-module.

Usage in sub-module:

import dayjs from 'dayjs';
import customParseFormat from 'dayjs/plugin/customParseFormat';
import dayjsIsBetween from 'dayjs/plugin/isBetween';
import utc from 'dayjs/plugin/utc';
import timezone from 'dayjs/plugin/timezone';
dayjs.extend(customParseFormat);
dayjs.extend(dayjsIsBetween);
dayjs.extend(utc);
dayjs.extend(timezone);

Information

• Day.js Version: v1.9.4
• OS: Mac
• Browser Terminal

[iamkun]

A reproduction repo, please?

[spsaucier-bakkt]

This was resolved when I added dayjs to the app that consumes the library which uses dayjs. Not sure why that would be required.

[rogerprz]

This was resolved when I added dayjs to the app that consumes the library which uses dayjs. Not sure why that would be required.

Can you explain what you mean? Added where in the app?

[spsaucier-bakkt]

That's a good question 🤔
I wrote that very vaguely, and I don't remember what I meant.

[JenuelDev]

I dont know if its in codesanbox that's making the error,, but here is the example of an error,,, cant find module.
https://codesandbox.io/s/dayjs-playground-forked-mqd4u?file=/src/index.js

[bartosjiri]

I had a similar problem when compiling a production build of a SvelteKit app. The solution, as console error has suggested, was to add the .js extension to the import path:

Example:
import timezone from 'dayjs/plugin/timezone'; -> import timezone from 'dayjs/plugin/timezone.js';

[mohas]

but why?

[vhscom]

Using PNPM a related error appeared as:

Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/src/svelte-headlessui-starter/node_modules/dayjs/plugin/weekOfYear' imported from /src/svelte-headlessui-starter/.svelte-kit/output/server/entries/pages/calendar.svelte.js
Did you mean to import dayjs@1.11.0/node_modules/dayjs/plugin/weekOfYear.js?

Adding .js to the dayjs/plugin imports as suggested by @bartosjiri and mentioned in sveltejs/kit#699 cleared things up.

[vhscom]

More about what's causing this error with bare imports: https://nodejs.org/api/esm.html#esm_mandatory_file_extensions
Learned about it here: tailwindlabs/tailwindcss#5089 (comment)

[nahumzs]

but why?

If you are using playwright, It has to do with module resolution, typescript and js, don't remember where I read it but I know is close enough to that situation. I someone can add a more extensive description would be great.