Firebase Emulator error when writing/updating document inside a Firestore trigger, when using snapshot.ref.set()

[ralcar]

[REQUIRED] Environment info

firebase-tools:
7.4.0

Platform:
Windows

[REQUIRED] Test case

Since auth is not available in the context for Firestore triggers, I send along some user data in the snapshot to log the activity and use the user token to create some extra steps inside the onCreate function. I extract the userdata from the snapshot and the want to remove the userdata using the snapshot.ref.set(snapShotWithoutUserData)

[REQUIRED] Steps to reproduce

export const onOrganizerCreate = functions.firestore.document("organizers/{organizerId}")
.onCreate((snapshot, context) => {
  return snapshot.ref.set({
    test: "testing"
  }, { merge: true });
})

I have tried ref.set(), ref.update() with or without the merge parameter, same result

[REQUIRED] Expected behavior

Expect it to run without errors as it does when i deploy it.

[REQUIRED] Actual behavior

The emulator/trigger crashes, giving this error

If i deploy the same code and run it without the emulator, it works just fine. Or if i use the firebase-admin to do the same task by building the path using the context params, it also works

! Non-default "firebase-admin" instance created!

• This instance will not be mocked and will access production resources.
  ! Google API requested!
• URL: "https://oauth2.googleapis.com/token"
• Be careful, this may be a production service.
  ! functions: Error: Getting metadata from plugin failed with error: invalid_grant
  at Http2CallStream.call.on (C:\Development<projectId>\functions\node_modules@grpc\grpc-js\build\src\client.js:96:45)
  at Http2CallStream.emit (events.js:194:15)
  at Http2CallStream.EventEmitter.emit (domain.js:441:20)
  at process.nextTick (C:\Development<projectId>\functions\node_modules@grpc\grpc-js\build\src\call-stream.js:71:22)
  at process._tickCallback (internal/process/next_tick.js:61:11)
  ! Your function was killed because it raised an unhandled error.
  (node:13324) UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are
  sent to the client
  at ServerResponse.setHeader (_http_outgoing.js:470:11)
  at ServerResponse.header (C:\Users\ralcar\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\express\lib\response.js:771:10)
  at ServerResponse.send (C:\Users\ralcar\AppData\Roaming\npm\node_modules\firebase-tools\node_modules\expressginated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 2)

[samtstern]

@ralcar thanks that's an interesting bug, I think I can see how it happened.

For now you can workaround this by doing:

const newRef = admin.firestore().doc(snapshot.ref.path);
return newRef.set({ ... });

This will construct a new reference using the emulated admin.firestore().

[samtstern]

Note to self:
https://github.com/firebase/firebase-functions/blob/master/src/apps.ts#L107

I think we could get around this by initializing an app with the name __admin__ in the emulators as a way of tricking the firebase-functions library to use our mocks. It would be relying on an internal implementation detail but I don't see how it would be harmful.

[ralcar]

Thank you for the quick answer, that worked great, thank you! Was worried i was going to have to build that path everywhere. This is cleaner, but I hope I could avoid importing the firebase-admin at all in the future ;).

Just for some more help with the debugging, i initializeApp on two different databases during bootup of the cloud functions. And i am locally on Node 10.15.1

[samtstern]

@ralcar could you show the code where you initializeApp twice? It would be helpful so that I can recreate the situation.

[larssn]

I saw something similar using snapshot.ref.update() (also inside a trigger), which claimed the document didn't exist. Maybe related.

Weirdly enough though, snapshot.ref.set(doc, {merge: true}); worked without errors.

[samtstern]

@larssn that sounds correct. .update() operations fail if the document does not exist. .set() operations create the document if it doesn't exist. set(data, { merge: true }) on a non-existent document is identical to set(data).

[larssn]

Sorry, I should have mentioned what kind of trigger it was, as it was the onCreate trigger.
The document should exist at that point I take it? In any case, it was easily solved using set.

[ralcar]

@samtstern ofcourse, here it is!
My /functions/src/index.ts loads "main.ts" first, that looks like this:

import { config } from 'firebase-functions';
import { initializeApp, credential } from 'firebase-admin';
initializeApp(config().firebase);

const productionServiceAccount = require("../<production>.json");
const stagingServiceAccount = require("../<staging>.json");

initializeApp({
  credential: credential.cert(productionServiceAccount),
  databaseURL: "<url>"
}, "production");

initializeApp({
  credential: credential.cert(stagingServiceAccount),
  databaseURL: "<url>"
}, "staging");

export * from 'firebase-functions';

[samtstern]

@ralcar thanks!

FYI initializeApp(config().firebase) is outdated, you should just use initializeApp() ... that doesn't change the bug here but it's worth noting.

[samtstern]

@larssn yes the doc should definitely exist at this point. I worry that your code is talking to prod sometimes ... changing it to set() may have fixed the symptom but covered up the bug.

[samtstern]

Working on this over here:
firebase/firebase-functions#565

[samtstern]

The fix for this issue has been released in version 7.6.0