Options object not supported for Firestore snapshot listener

[jperasmus]

• Operating System version: MacOS Mojave (v10.14.2)
• Firebase SDK version: v7.0.0
• Firebase Product: firestore

Describe the problem

Firebase reference documentation states that you can have an options object as the first argument for the DocumentReference.onShapshot() method. This works for the firebase JavaScript client SDK, but not for this Node.js SDK.

Specifying an options object for this package produces the following error:

node_modules/@google-cloud/firestore/build/src/validate.js:93
                    throw new Error(message);
                    ^

Error: Argument "onNext" is not a valid function.
    at Validator.(anonymous function).values [as isFunction] (node_modules/@google-cloud/firestore/build/src/validate.js:93:27)
    at Query.onSnapshot (node_modules/@google-cloud/firestore/build/src/reference.js:1485:25)
    at Object.subscribeRaw (flamelink-js-sdk/packages/schemas/dist/cjs/cf/index.js:1864:29)
    at Object.subscribe (flamelink-js-sdk/packages/schemas/dist/cjs/cf/index.js:1871:24)
    at flamelink-js-sdk/packages/schemas/dist/cjs/cf/index.js:2004:21
    at Array.forEach (<anonymous>)
    at subscribeAndCacheSchemas (flamelink-js-sdk/packages/schemas/dist/cjs/cf/index.js:2003:24)
    at factory (flamelink-js-sdk/packages/schemas/dist/cjs/cf/index.js:2023:5)
    at schemas (flamelink-js-sdk/packages/schemas/dist/cjs/index.js:13:62)
    at flamelink-js-sdk/packages/app/dist/index.node.cjs.js:1249:24

Based on what I could tell, the problem is that this method is only expecting the first argument to be the onNext function:

This code is actually in the @google-cloud/firestore/build/src/reference.js package, but that does not seem to be publicly available apart from via this repo.

Steps to reproduce:

• Initialize Firebase admin app
• Setup listener for a Firestore collection with the first argument an options object

Relevant Code:

const admin = require('firebase-admin')

const adminApp = admin.initializeApp({
  credential: <setup-credentials>
  ),
  databaseURL: 'https://something.firebaseio.com'
})

adminApp
  .firestore()
  .collection('someCollection')
  .onSnapshot(
    {
      includeMetadataChanges: true
    },
    onNextCallback,
    onErrorCallback
  )

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[jperasmus]

Here is how the client SDK handles it: https://github.com/firebase/firebase-js-sdk/blob/6a0154aee104a163d6d3b1a28d80fcbb9bace908/packages/firestore/src/api/database.ts#L971

[hiranya911]

You're comparing JS SDK's API reference docs against the Firestore Node.js SDK. They have slightly different API surfaces. The server-side Node.js SDK does not support an options argument: https://cloud.google.com/nodejs/docs/reference/firestore/0.20.x/DocumentReference#onSnapshot

[hiranya911]

Assigning to the Firestore SDK team to comment on if this option should be added to the server-side SDK.

[wilhuff]

@hiranya911 is correct. There are no snapshot listener options in the server-side node SDK.

In particular, the includeMetadataChanges option doesn't exist there because those kinds of transitions only happen when there's a local cache involved. The server-side SDKs have no cache.

[jperasmus]

Thanks, @hiranya911 and @wilhuff

It makes sense what you say about the includeMetadataChanges option specifically.

The thing that confused me was reading the Firebase reference docs and clicking the links under the Node.js (client) section, it actually takes you back to the standard JS docs.

This is my mistake. Thanks for your time.