Allow exportAs transformation to access the current task output

[mcruzdev]

Description

When using exportAs with a JavaContextFunction that accesses workflowContext.instanceData().input(), the method returns null instead of the original workflow input, causing a NullPointerException.

Expected Behavior

workflowContext.instanceData().input() should return the original workflow input data that was passed to def.instance(submission).start().

Actual Behavior

workflowContext.instanceData().input() returns null, causing:

java.lang.NullPointerException
at java.base/java.util.Optional.of(Optional.java:113)
at io.serverlessworkflow.impl.model.jackson.JacksonModel.convert(JacksonModel.java:99)
at io.serverlessworkflow.impl.AbstractWorkflowModel.as(AbstractWorkflowModel.java:45)

Minimal Reproducer

import static io.serverlessworkflow.fluent.func.dsl.FuncDSL.function;
import io.serverlessworkflow.api.types.Workflow;
import io.serverlessworkflow.fluent.func.FuncWorkflowBuilder;
import io.serverlessworkflow.impl.WorkflowApplication;
import io.serverlessworkflow.impl.WorkflowContextData;
import io.serverlessworkflow.impl.WorkflowDefinition;
import io.serverlessworkflow.impl.WorkflowModel;

public class WorkflowContextInputTest {
    
    public record Input(String name, int value) {}
    public record Output(int result) {}
    public record Combined(String name, int result) {}
    
    public static void main(String[] args) {
        Workflow workflow = FuncWorkflowBuilder.workflow("test")
            .tasks(
                // Step 1: Process input
                function("process",
                    (Input input) -> new Output(input.value() * 2),
                    Input.class)
                .exportAs(
                    (Output output, WorkflowContextData context) -> {
                        // ❌ THIS RETURNS NULL:
                        WorkflowModel originalInput = context.instanceData().input();
                        Input input = originalInput.as(Input.class).orElseThrow();
                        
                        return new Combined(input.name(), output.result());
                    },
                    Output.class)
            )
            .build();
        
        WorkflowApplication app = WorkflowApplication.builder().build();
        WorkflowDefinition def = app.workflowDefinition(workflow);
        
        // This will throw NullPointerException
        WorkflowModel result = def.instance(new Input("test", 5)).start().join();
    }
}

Workaround

Pass data forward through the workflow steps instead of accessing it from the context:

function("process",
    (Input input) -> new Combined(input.name(), input.value() * 2),
    Input.class)

[fjtirado]

There is a wrong expectation in the type of the exportAs first parameter. The exportAs first parameter is the current context, not current task output. This is done on purpose to be aligned with the spec expectation for jq expression, see example here

To achieve what you are trying to do, we will need a third parameter, the taskcontext, where user will be able to access the task output

[mcruzdev]

There is a wrong expectation in the type of the exportAs first parameter. The exportAs first parameter is the current context, not current task output. This is done on purpose to be aligned with the spec expectation for jq expression, see example here

To achieve what you are trying to do, we will need a third parameter, that taskcontext, where user will be able to access the task output

Now I can see, I want to update some parameters names and documentation, I think I can add it to outputAs too.

[fjtirado]

Its already there, this is how the example should look like

public static void main(String[] args) {
    Workflow workflow =
        FuncWorkflowBuilder.workflow("test")
            .tasks(
                // Step 1: Process input
                function("process", (Input input) -> new Output(input.value() * 2), Input.class)
                    .exportAs(
                        (__, workflowContext, taskContext) -> new Combined(workflowContext.instanceData().input().as(Input.class).orElseThrow().name(), taskContext.output().as(Output.class).orElseThrow().result())))
            .build();

    WorkflowApplication app = WorkflowApplication.builder().build();
    WorkflowDefinition def = app.workflowDefinition(workflow);

    // This will throw NullPointerException
    WorkflowInstance instance = def.instance(new Input("test", 5));
    System.out.println(instance.start().join().asJavaObject());
    System.out.println(instance.context().asJavaObject());
  }