Firestore arrayUnion() silently drops server timestamp values

[jwngr]

Environment

• Operating System version: All
• Firebase SDK version: 6.0.0
• Firebase Product: Firestore

Problem

Thanks for adding the new admin.firestore.FieldValue.arrayUnion() and admin.firestore.FieldValue.arrayRemove() features. They're super handy! I think I found a bug in it though. When you try to add an item which contains admin.firestore.FieldValue.serverTimestamp() via admin.firestore.FieldValue.arrayUnion(), the timestamp is never set and the corresponding field is dropped.

Steps to reproduce:

1. Run the repro below.

Expected result:

The database should look like this:

Actual result:

The database ends up looking like this:

If you switch the non-working admin.firestore.FieldValue.serverTimestamp() with new Date(), the expected result occurs.

Relevant Code:

return admin.firestore().doc('items/2').set({
  someArray: admin.firestore.FieldValue.arrayUnion({
    createdAt: admin.firestore.FieldValue.serverTimestamp(),
    foo: 'bar',
  }),
})
  .then(() => console.log('Success!'))
  .catch((error) => console.log('Error:', error));

Note that this also fails, resulting an an empty someArray array:

return admin.firestore().doc('items/2').set({
  someArray: admin.firestore.FieldValue.arrayUnion(
    admin.firestore.FieldValue.serverTimestamp()
  ),
})
  .then(() => console.log('Success!'))
  .catch((error) => console.log('Error:', error));

[google-oss-bot]

Hmmm this issue does not seem to follow the issue template. Make sure you provide all the required information.

[google-oss-bot]

Hey there! I couldn't figure out what this issue is about, so I've labeled it for a human to triage. Hang tight.

[schmidt-sebastian]

Hey "jwngr", thanks for filing this issue. Note that we currently don't support Server Timestamps inside of Array values. It looks like we are missing some client-side validation here. We will add it shortly.