Is there an alternative to writeFields?

问题

This article stated that "[writeFields] is now deprecated".
Additionally, I cannot find any documentation for writeFields, it is not even listed as part of Request in the documentation anymore.

Problem

The problem I am facing with Cloud Firestore Security Rules is that verifying that only particular fields are modified requires massive amounts of conditions.
For example, if I want to verify that the only modified value of a document is cakes, I have to write the following rule:

allow update: if request.resource.data.size() == 20
              && request.resource.data.likes == resource.data.likes
              && request.resource.data.name == resource.data.name
              && request.resource.data.date == resource.data.date
              && request.resource.data.body == resource.data.body
              && request.resource.data.title == resource.data.title
              && request.resource.data.tags == resource.data.tags
              && request.resource.data.comments == resource.data.comments
              && request.resource.data.answers == resource.data.answers
              && request.resource.data.awards == resource.data.awards
              && request.resource.data.image == resource.data.image
              && request.resource.data.link == resource.data.link
              && request.resource.data.format == resource.data.format
              && request.resource.data.type == resource.data.type
              && request.resource.data.user == resource.data.user
              && request.resource.data.views == resource.data.views
              && request.resource.data.reports == resource.data.reports
              && request.resource.data.roles == resource.data.roles
              && request.resource.data.category == resource.data.category
              && request.resource.data.votes == resource.data.votes
              && request.resource.data.cakes is int;

Using writeFields, the exact same rule would have looked like this:

allow update: if request.writeFields.hasOnly(['cakes']) && request.resource.data.cakes is int;

What can I do to decrease the code size of my rules / what is the alternative to writeFields?

Limits

There are two limits mentioned in the documentation that make this problem even worse:

Maximum number of expressions evaluated per request: 1,000
Maximum size of a ruleset: 64 KB

I expect to reach both of these at some point with this limitation.

回答1:

Yes! There is now a replacement called "Map Diffs". Check this syntax out:

allow update: if request.resource.data.diff(resource.data).affectedKeys().hasOnly(['cakes']) 
              && request.resource.data.cakes is int;

回答2:

Unfortunately, what you're doing right now is currently your best option.

The Firebase rules team is working on a language improvement to make it easier to compare/diff map type objects, which will drastically cut down on the number of expressions it takes to do this sort of thing, but there is no timeline for that right now. Please stay tuned.

来源：https://stackoverflow.com/questions/58681738/is-there-an-alternative-to-writefields

标签

firebase

google-cloud-firestore

firebase-security