Incompatible conversion from Pub/Sub emulator to CloudEvent for `CloudEventsFunction`

[campbellatslang]

In invoker/core/src/main/java/com/google/cloud/functions/invoker/Event.java, the conditional check for messages originating from the Pub/Sub emulator strips the name field, which is incompatible with this repository's conversion from legacy events to CloudEvent, throwing an exception when calling Resource.from because Resource.name is not nullable. This makes use of CloudEventFunction incompatible with a Pub/Sub emulator setup for local development.

Example stack trace:

2026-02-23 17:25:21 com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Missing required properties: name
2026-02-23 17:25:21     at com.google.gson.Gson.fromJson(Gson.java:1381)
2026-02-23 17:25:21     at com.google.gson.Gson.fromJson(Gson.java:1259)
2026-02-23 17:25:21     at com.google.gson.Gson.fromJson(Gson.java:1169)
2026-02-23 17:25:21     at com.google.gson.Gson.fromJson(Gson.java:1106)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.CloudFunctionsContext$Resource.from(CloudFunctionsContext.java:109)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.GcfEvents$EventAdapter.convertToCloudEvent(GcfEvents.java:143)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.GcfEvents.convertToCloudEvent(GcfEvents.java:116)
2026-02-23 17:25:21     at
com.google.cloud.functions.invoker.BackgroundFunctionExecutor$CloudEventFunctionExecutor.serviceLegacyEvent(BackgroundFunctionExecutor.java:325)
2026-02-23 17:25:21     at
com.google.cloud.functions.invoker.BackgroundFunctionExecutor.lambda$serviceLegacyEvent$8(BackgroundFunctionExecutor.java:402)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.runWithContextClassLoader(BackgroundFunctionExecutor.java:409)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.serviceLegacyEvent(BackgroundFunctionExecutor.java:402)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.BackgroundFunctionExecutor.handle(BackgroundFunctionExecutor.java:345)
2026-02-23 17:25:21     at org.eclipse.jetty.server.handler.EagerContentHandler.onConditionsMet(EagerContentHandler.java:155)
2026-02-23 17:25:21     at org.eclipse.jetty.server.handler.ConditionalHandler.handle(ConditionalHandler.java:378)
2026-02-23 17:25:21     at org.eclipse.jetty.server.Handler$Wrapper.handle(Handler.java:794)
2026-02-23 17:25:21     at com.google.cloud.functions.invoker.runner.Invoker$NotFoundHandler.handle(Invoker.java:498)
2026-02-23 17:25:21     at org.eclipse.jetty.server.Server.handle(Server.java:195)
2026-02-23 17:25:21     at org.eclipse.jetty.server.internal.HttpChannelState$HandlerInvoker.run(HttpChannelState.java:680)
2026-02-23 17:25:21     at org.eclipse.jetty.server.internal.HttpConnection.onFillable(HttpConnection.java:411)
2026-02-23 17:25:21     at org.eclipse.jetty.server.internal.HttpConnection$FillableCallback.succeeded(HttpConnection.java:1809)
2026-02-23 17:25:21     at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:105)
2026-02-23 17:25:21     at org.eclipse.jetty.io.SelectableChannelEndPoint$1.run(SelectableChannelEndPoint.java:54)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.runTask(AdaptiveExecutionStrategy.java:492)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.epcRunTask(AdaptiveExecutionStrategy.java:428)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.consumeTask(AdaptiveExecutionStrategy.java:401)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.tryProduce(AdaptiveExecutionStrategy.java:255)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.run(AdaptiveExecutionStrategy.java:204)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:312)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:1009)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.doRunJob(QueuedThreadPool.java:1239)
2026-02-23 17:25:21     at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1194)
2026-02-23 17:25:21     at java.base/java.lang.Thread.run(Unknown Source)
2026-02-23 17:25:21 Caused by: java.lang.IllegalStateException: Missing required properties: name
2026-02-23 17:25:21     at
com.google.cloud.functions.invoker.$AutoValue_CloudFunctionsContext_Resource$Builder.build($AutoValue_CloudFunctionsContext_Resource.java:108)
2026-02-23 17:25:21     at
com.google.cloud.functions.invoker.AutoValue_CloudFunctionsContext_Resource$GsonTypeAdapter.read(AutoValue_CloudFunctionsContext_Resource.java:118)
2026-02-23 17:25:21     at
com.google.cloud.functions.invoker.AutoValue_CloudFunctionsContext_Resource$GsonTypeAdapter.read(AutoValue_CloudFunctionsContext_Resource.java:25)
2026-02-23 17:25:21     at com.google.gson.Gson.fromJson(Gson.java:1358)
2026-02-23 17:25:21     ... 31 more
2026-02-23 17:25:21

This issue does not affect BackgroundFunction as Resource.from is not called when servicing legacy events without conversion.

[taeold]

Hey thanks for filing the issue.

After reviewing the code, I learned that Pubsub emulator doesn't send the Pubsub topic, and functions framework here is throwing an runtime error because of that.

Node.js functions framework seems to have special handling to support Pubsub emulator use case that Java functions frameowork lacks:

https://github.com/GoogleCloudPlatform/functions-framework-nodejs/blob/243202d5e133bb11257f570c63154f335d2e61bd/src/pubsub_middleware.ts#L113

I'm going to mark the issue as enhancement and figure out how we could prioritize this work. Thanks for you patience.