PubsubIO.fromSubscription(ValueProvider) throws RuntimeException

The very simple Pipeline:

public class PubsubTemplate {
public interface PubsubTemplateOptions extends PipelineOptions

{ ValueProvider getSubscription(); void setSubscription(ValueProvider value); }

public static void main(String[] args) throws IOException

{ PubsubTemplateOptions options = PipelineOptionsFactory.fromArgs(args).withValidation() .as(PubsubTemplateOptions.class); Pipeline p = Pipeline.create(options); p.apply(PubsubIO.readStrings(). fromSubscription(options.getSubscription())); p.run().waitUntilFinish(); }

}

Throws the exception when generating a Dataflow template:

java.lang.reflect.InvocationTargetException
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:293)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.RuntimeException: Not called from a runtime context.
at org.apache.beam.sdk.options.ValueProvider$RuntimeValueProvider.get(ValueProvider.java:223)
at org.apache.beam.sdk.options.ValueProvider$NestedValueProvider.get(ValueProvider.java:131)
at org.apache.beam.sdk.options.ValueProvider$NestedValueProvider.get(ValueProvider.java:131)
at org.apache.beam.sdk.io.gcp.pubsub.PubsubUnboundedSource.getSubscription(PubsubUnboundedSource.java:1374)
at org.apache.beam.sdk.io.gcp.pubsub.PubsubUnboundedSource$PubsubSource.(PubsubUnboundedSource.java:1103)
at org.apache.beam.sdk.io.gcp.pubsub.PubsubUnboundedSource.expand(PubsubUnboundedSource.java:1407)
at org.apache.beam.sdk.io.gcp.pubsub.PubsubUnboundedSource.expand(PubsubUnboundedSource.java:110)
at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:514)
at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:454)
at org.apache.beam.sdk.values.PBegin.apply(PBegin.java:44)
at org.apache.beam.sdk.io.gcp.pubsub.PubsubIO$Read.expand(PubsubIO.java:730)
at org.apache.beam.sdk.io.gcp.pubsub.PubsubIO$Read.expand(PubsubIO.java:536)
at org.apache.beam.sdk.Pipeline.applyInternal(Pipeline.java:514)
at org.apache.beam.sdk.Pipeline.applyTransform(Pipeline.java:454)
at org.apache.beam.sdk.values.PBegin.apply(PBegin.java:44)
at org.apache.beam.sdk.Pipeline.apply(Pipeline.java:165)
at com.google.pubsubtemplate.PubsubTemplate.main(PubsubTemplate.java:34)
... 6 more

Imported from Jira [BEAM-2965](https://issues.apache.org/jira/browse/BEAM-2965). Original Jira may contain additional context.
Reported by: bmenasha.

Start with the PubsubIO.readStrings().fromSubscription(...) entry point and inspect PubsubUnboundedSource.getSubscription at line 1374, using the provided Dataflow template example to reproduce the failure. Done means template generation accepts the ValueProvider subscription without throwing "Not called from a runtime context."

Written by the indexing model from the issue text.