Allow discoverReferenceBuild to run on Agent none

[noah-wolton]

What feature do you want to see added?

Sorry not sure if I'm creating this issue in the right place, so apologies in advance if I'm not.

I was wondering if there was a reason why discoverReferenceBuild cannot be called if there is no node/workspace present. From my understanding it seems like it's trying to use the SCM to determine a baseline and that requires a workspace, but for certain use cases I don't need it to worry about that and it would be great if there was an option for it just to use the latest build and therefore wouldn't need a node to run on.

Upstream changes

No response

Are you interested in contributing this feature?

Obviously if this is a difficult change then it's probably not worth it -- in my naivete I'd hoped it would be just a simple change to getRequiredContext and I could offer some code, but it looks significantly more complex than my limited Jenkins experience is suited to.

[uhafner]

What happens exactly when you call it without a node? There are no restrictions as far as I remember, I even do not use getRequiredContext , it is a Publisher and not a workflow step with context.

[noah-wolton]

When run with agent none I get:

Found unhandled org.jenkinsci.plugins.workflow.steps.MissingContextVariableException exception:
Required context class hudson.FilePath is missing
Perhaps you forgot to surround the step with a step that provides this, such as: node, dockerNode
	PluginClassLoader for workflow-basic-steps//org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:90)
	PluginClassLoader for workflow-basic-steps//org.jenkinsci.plugins.workflow.steps.CoreStep$Execution.run(CoreStep.java:71)
	PluginClassLoader for workflow-step-api//org.jenkinsci.plugins.workflow.steps.SynchronousNonBlockingStepExecution.lambda$start$0(SynchronousNonBlockingStepExecution.java:49)
	java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:572)
	java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
	java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
	java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
	java.base/java.lang.Thread.run(Thread.java:1583)

And:
Attempted to execute a step that requires a node context while ‘agent none’ was specified. Be sure to specify your own ‘node { ... }’ blocks when using ‘agent none’.

[uhafner]

Is this related to the reference job action? I don't see it referenced in the stacktrace.

(Maybe the problem is, that there is no extra step for the reference job, it simply is implemented for freestyle jobs.)

[noah-wolton]

It is a strange error as it doesn't seem to appear in the console log, you can only see it in the pipeline overview:

In the console log you only get:
ERROR: Attempted to execute a step that requires a node context while ‘agent none’ was specified. Be sure to specify your own ‘node { ... }’ blocks when using ‘agent none’.

[uhafner]

I see. One option would be, to implement a simple step that uses a different context.

Currently it uses the Freestyle API:

public void perform(@NonNull final Run<?, ?> run, @NonNull final FilePath workspace, @NonNull final EnvVars env,
            @NonNull final Launcher launcher, @NonNull final TaskListener listener) {

but the workspace is actually not used.