en-GB locale format changes in 20.12.1

[Mezzle]

Version

v20.12.1

Platform

Darwin cube.local 23.4.0 Darwin Kernel Version 23.4.0: Fri Mar 15 00:12:49 PDT 2024; root:xnu-10063.101.17~1/RELEASE_ARM64_T6020 arm64 arm Darwin

Subsystem

No response

What steps will reproduce the bug?

Test case:

https://github.com/Mezzle/node-date-format-bug

Same code run in both 20.11.1 and 20.12.1 returns different results.

 ❯ cd 20.11
Using Node v20.11.1
 ❯ node test.js
Mon, 8 April 2024 at 11:47
 ❯ cd ../20.12
Using Node v20.12.1
 ❯ node test.js
Mon 8 April 2024 at 11:47

How often does it reproduce? Is there a required condition?

No response

What is the expected behavior? Why is that the expected behavior?

it is expected that the date is consistent across versions.

What do you see instead?

I see that 20.12.1 has a missing , difference.

Additional information

No response

[climba03003]

According to #51090 (comment)
The output is not guarantee to be the same over the same major.
You should never rely on the output of formatted date.

node@20.12.0 updates ICU to 74.2. Includes CLDR 44.1 and Unicode 15.1.

[RedYetiDev]

As @climba03003 mentioned, I don't believe this is an issue, but a feature that comes with updating Node.JS, if you disagree, please elaborate on your concern.

Thank you!

[Mezzle]

My concern regarding this is that - in a minor version change, there is a backwards compatibility break. If you transition from 20.11->20.12, and rely on this functionality, it's broken, which goes against the semver I believe Node uses

I don't believe these changes are documented anywhere (at least they weren't noticable), and I didn't expect a BC break with a minor version.

[RedYetiDev]

It may seem like a backwards compatibility break, but it's just keeping the Unicode standard. All of this locale formatting is standardized by Unicode, so we are just following the changes.