util.format with array is different in Node.js 12

[rosen-vladimirov]

• Version: 12.9.1
• Platform: Linux rvladimirov-ubuntu 5.0.0-25-generic #26~18.04.1-Ubuntu SMP Thu Aug 1 13:51:02 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux (same happens on macOS Mojave as well, probably on Windows)
• Subsystem: util

The result of util.format had changed in Node.js 12:

util.format("result: %s", [ 1, 2])

Node.js 10.15.3 (and in fact all versions below 12): result: 1,2
Node.js 12.9.1 (in fact all 12.x.x versions): result: [ 1, 2 ]

Is this an intentional change?

[addaleax]

Yes, see #26927 (and, to lesser degree, #27621). I’ve added the semver-major label now, because I think it should definitely have gotten it. That doesn’t automatically affect the changelog, but we can modify that to, if necessary.

[rosen-vladimirov]

Hey @addaleax ,
Thanks for the fast response. I was looking for this in the Changelog and I've decided to create an issue as I did not find it there. Anyway, as this change is intentional, I'm closing this thread. Just FYI we were relying on the mentioned behavior in our code and our unit tests caught the change of the behavior. Anyway, we'll take a look how to resolve it in our product.
Thanks again!