IllegalStateException with Google App Engine Local Datastore

Question

So I'm trying to run a Google App Engine with the Datastore locally to test and debug. The local App Engine seems to work on its own, as does the datastore emulator.

But as soon as I set the environment variables for the datastore emulator, and restart the local App Engine, it crashes with the error,

Caused by: java.lang.IllegalStateException: Must use project ID as app ID if project ID is provided. 

I've attached a more complete stack trace below

From the error message, I suspected I need to change my project id to the project name instead. So I tried replacing various instances of the project id with the project name where I could and unfortunately this did not work either.

Commands I'm running:

1. gcloud config set project PROJECT-ID
2. export ENDPOINTS_SERVICE_NAME=name.endpoints.PROJECT-ID.cloud.goog
3. gcloud beta emulators datastore start
4. $(gcloud beta emulators datastore env-init)
5. mvn appengine:run

I've put the stack trace on pastebin https://pastebin.com/atcnYwrq

Answer 1

I happened to stumble into a way to fix this.

export DATASTORE_USE_PROJECT_ID_AS_APP_ID=true