formatters.mjs export issue

[houd1ni]

format(new Date(), 'yyyy') results in Uncaught TypeError: _formattersMjs.formatters is undefined

It's simple (almost sample) Parcel v 2.12.0 project with this config in package.json:

  "@parcel/resolver-default": {
    "packageExports": true
  }

[fturmel]

That's really helpful, and related to #3670. It definitely looks like a Parcel bug (possibly 2?) and not specific to Plasmo's usage of Parcel.

I spent some time troubleshooting (I keep getting nerd-snipped here lol), and I got some additional info:

Re-exporting an import also used in the module that imports it breaks Parcel in dev/watch mode

Breaks:
The formatters get tree-shaken unless the re-exports are consumed by the app even though they are also used in the format function itself. If've described this in the other issue in greater details. This was introduced in date-fns 3.2.0.

date-fns/src/format/index.ts

Lines 3 to 4 in 5c1adb5

	import { formatters } from "../_lib/format/formatters/index.js";
	import { longFormatters } from "../_lib/format/longFormatters/index.js";

date-fns/src/format/index.ts

Lines 20 to 22 in 5c1adb5

	// Rexports of internal for libraries to use.
	// See: https://github.com/date-fns/date-fns/issues/3638#issuecomment-1877082874
	export { formatters, longFormatters };

Possible workaround:
If we assign the imports to new constants and export those, it seems to be OK.

import { formatters as _formatters } from "./_lib/format/formatters.mjs";
import { longFormatters as _longFormatters } from "./_lib/format/longFormatters.mjs";
...
export const formatters = _formatters;
export const longFormatter = _longFormatters;

export {x as y} syntax breaks Parcel prod build

Breaks:
@parcel/core: node_modules/date-fns/index.mjs does not export 'format'
Introduced in date-fns 3.3.0

date-fns/src/format/index.ts

Line 46 in 5c1adb5

export { format as formatDate };

Possible workaround:
Similarly to the previous issue, assigning to a new constant that is exported seems to fix the problem.

export const formatDate = format;

---

Other bundlers don't have these problems AFAIK, so it should be reported to the Parcel team.

As demonstrated here, there appears to be workarounds that could be implemented in date-fns. They would not address the root cause though. @kossnocorp

date-fns v3.1.0 and earlier should work, so you can also try downgrading temporarily until this is resolved.

(@seaders this might be of interest to you)

[shepmaster]

I had this same problem, but was unable to reproduce it in a clean project. Eventually, I deleted my .parcel-cache in the original project that was experiencing the problem and could no longer reproduce it there either. 🤷

[Ziqi-Yang]

Another issue there ( it only occurs in production mode, i.e. parcel build):

bun parcel build 'templates/**/*.j2'
🚨 Build failed.

@parcel/core: node_modules/date-fns/index.mjs does not export 'format'

  /home/meowking/proj/class_proj/COMP3030J-SE-P2-G1/proj/static/js/chart/basic.ts:5:10
    4 | 
  > 5 | import { format } from 'date-fns';
  >   |          ^^^^^^
    6 | 
    7 | // temporary workaround for parcel tree-shaking error for date-fns

error: "parcel" exited with code 1
error: Recipe `parcel-build` failed on line 90 with exit code 1

[isakstarlander]

Hey! I ran into this same issue after upgrading date-fns from version 2.x to the latest version 3.6.0. Did some investigation and could make a reproduction of the issue in a bare parcel + date-fns repo. https://github.com/Milkywire/date-fns-parcel-reproduction

The real interesting part is that plain javascript works perfectly, but the typescript one fails.

Also noticed this PR related to a duplicate export which caused some issues, could be worth keeping an eye out on the effects of that PR getting merged.