Firestore - WriteBatch.Set ignoring {merge: true} when using FieldValue.increment

[L1b3rtyy]

[REQUIRED] Describe your environment

• Operating System version: _____ Windows 10
• Browser version: _____ Chrome (latest Version 81.0.4044.129) but this seems irrelevant as it is not working in the emulator either
• Firebase SDK version: _____ firebase@7.14.3, @firebase/testing@0.19.3
• Firebase Product: _____ Firestore, Testing (auth, database, storage, etc)

[REQUIRED] Describe the problem

Updating a document with FieldValue.increment using a batch via the set function and the {merge: true} option fails. Looking at the logs it seems it is ignoring the option and trying to overwrite the document.

batch.update(somepath, {counter: firebase.firestore.FieldValue.increment(1)})
=> works as expected
batch.set(somepath, {counter: firebase.firestore.FieldValue.increment(1), {merge: true})
=> will reset counter to 1 whatever its previous value

https://firebase.google.com/docs/reference/js/firebase.firestore.FieldValue#increment
https://firebase.google.com/docs/firestore/manage-data/add-data#set_a_document
https://firebase.google.com/docs/reference/js/firebase.firestore.SetOptions

This is neither working in the emulator nor in Cloud Firestore.

Note that with the previous minor version firebase@7.14.2, @firebase/testing@0.19.2 - it is all working fine

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[amad9720]

I have exactly the same issue... I noticed it yesterday.
An explanation of this behavior will be great...
Thanks

[schmidt-sebastian]

This is indeed a regression. We will address this shortly.