I tried to start the datastore emulator in my local dev environment (Java 8) and got the following error. Looks to me it happens because of a mismatch of protobuf versions. It would be great if you know of any workaround for this. Thanks.
Cloud SDK Version: 313. OS: macOS
$ gcloud beta emulators datastore start
Executing: /Users/w/Work/google-cloud/google-cloud-sdk/platform/cloud-datastore-emulator/cloud_datastore_emulator create --project_id=<aaaa> /Users/w/.config/gcloud/emulators/datastore
[datastore] Oct 09, 2020 12:28:45 PM com.google.cloud.datastore.emulator.CloudDatastore$CreateAction$1 apply
[datastore] INFO: Provided project_id to Cloud Datastore emulator create command, which is no longer necessary.
[datastore] Created new Cloud Datastore project in '/Users/w/.config/gcloud/emulators/datastore'.
Executing: /Users/w/Work/google-cloud/google-cloud-sdk/platform/cloud-datastore-emulator/cloud_datastore_emulator start --host=localhost --port=8081 --store_on_disk=True --consistency=0.9 --allow_remote_shutdown /Users/w/.config/gcloud/emulators/datastore
[datastore] Oct 09, 2020 12:28:45 PM com.google.cloud.datastore.emulator.CloudDatastore$FakeDatastoreAction$9 apply
[datastore] INFO: Provided --allow_remote_shutdown to start command which is no longer necessary.
[datastore] Oct 09, 2020 12:28:45 PM com.google.cloud.datastore.emulator.impl.LocalDatastoreFileStub <init>
[datastore] INFO: Local Datastore initialized:
[datastore] Type: High Replication
[datastore] Storage: /Users/w/.config/gcloud/emulators/datastore/WEB-INF/appengine-generated/local_db.bin
[datastore] Exiting due to exception: java.lang.IllegalArgumentException: Extension is for type "proto2.MethodOptions" which does not match message type "google.protobuf.MethodOptions".