Bundling ESM exports using `vite` library mode doesn't work correctly

[sasivarnan]

Hi! 👋

Firstly, thanks for your work on this project! 🙂

I was facing an issue on my UI library that uses date-fns-tz/esm/*. My library setup uses vite with preserveModules option set to true.

The bundling was successful but during runtime the CJS libs that are imported within were throwing error.

Related:

1. https://github.com/marnusw/date-fns-tz/issues/193
2. https://github.com/marnusw/date-fns-tz/issues/200

After breaking my head for 2 days on this issue, today I used patch-package to patch date-fns-tz@1.3.7 for the project I'm working on.

I replaced the CJS imports with ESM imports under the date-fns-tz/esm directory.

Here is the diff that solved my problem:

diff --git a/node_modules/date-fns-tz/esm/format/index.js b/node_modules/date-fns-tz/esm/format/index.js
index 440e5a9..e1b6a3c 100644
--- a/node_modules/date-fns-tz/esm/format/index.js
+++ b/node_modules/date-fns-tz/esm/format/index.js
@@ -1,4 +1,4 @@
-import dateFnsFormat from 'date-fns/format/index.js'
+import dateFnsFormat from 'date-fns/esm/format/index.js'
 import formatters from './formatters/index.js'
 import toDate from '../toDate/index.js'

diff --git a/node_modules/date-fns-tz/esm/formatInTimeZone/index.js b/node_modules/date-fns-tz/esm/formatInTimeZone/index.js
index bbb2c4e..6763dc1 100644
--- a/node_modules/date-fns-tz/esm/formatInTimeZone/index.js
+++ b/node_modules/date-fns-tz/esm/formatInTimeZone/index.js
@@ -1,4 +1,4 @@
-import cloneObject from 'date-fns/_lib/cloneObject/index.js'
+import cloneObject from 'date-fns/esm/_lib/cloneObject/index.js'
 import format from '../format/index.js'
 import utcToZonedTime from '../utcToZonedTime/index.js'

diff --git a/node_modules/date-fns-tz/esm/toDate/index.js b/node_modules/date-fns-tz/esm/toDate/index.js
index 6acea0e..d4340cc 100644
--- a/node_modules/date-fns-tz/esm/toDate/index.js
+++ b/node_modules/date-fns-tz/esm/toDate/index.js
@@ -1,5 +1,5 @@
-import toInteger from 'date-fns/_lib/toInteger/index.js'
-import getTimezoneOffsetInMilliseconds from 'date-fns/_lib/getTimezoneOffsetInMilliseconds/index.js'
+import toInteger from 'date-fns/esm/_lib/toInteger/index.js'
+import getTimezoneOffsetInMilliseconds from 'date-fns/esm/_lib/getTimezoneOffsetInMilliseconds/index.js'
 import tzParseTimezone from '../_lib/tzParseTimezone/index.js'
 import tzPattern from '../_lib/tzPattern/index.js'

diff --git a/node_modules/date-fns-tz/esm/zonedTimeToUtc/index.js b/node_modules/date-fns-tz/esm/zonedTimeToUtc/index.js
index 4451b67..4ad4f50 100644
--- a/node_modules/date-fns-tz/esm/zonedTimeToUtc/index.js
+++ b/node_modules/date-fns-tz/esm/zonedTimeToUtc/index.js
@@ -1,4 +1,4 @@
-import cloneObject from 'date-fns/_lib/cloneObject/index.js'
+import cloneObject from 'date-fns/esm/_lib/cloneObject/index.js'
 import toDate from '../toDate/index.js'
 import tzPattern from '../_lib/tzPattern/index.js'
 import tzParseTimezone from '../_lib/tzParseTimezone/index.js'

This issue body was partially generated by patch-package.

Hope this workaround helps others.