DynamicFork auto-join has empty joinOn — JOIN task completes immediately without waiting for dynamic branches

[nthmost-orkes]

Summary

DynamicFork's companion JoinTask is constructed with zero arguments, producing empty joinOn: []. When added to a workflow, the JOIN task completes immediately — before any dynamic fork branches finish.

Tested against: Conductor OSS 3.32.0-rc.9

Root Cause

// Conductor/Definition/TaskType/DynamicFork.cs:32
public DynamicFork(string taskReferenceName, ...) : base(...)
{
    this.Join = new JoinTask(taskReferenceName + "_join");  // no joinOn args
    ...
}

JoinTask(string taskReferenceName, params WorkflowTask[] joinOn) — called with zero WorkflowTask args → JoinOn = new List<string>() on the companion join task.

When the user adds dynamicFork.Join to the workflow definition, the JOIN task has joinOn: []. The server's Join executor evaluates joinOn.stream().allMatch(...) — on an empty stream, allMatch returns true immediately — the JOIN transitions to COMPLETED without waiting for any dynamic fork branches.

Impact

Any workflow that uses DynamicFork.Join to obtain the join task will have a join that completes immediately. Dynamic tasks spawned by the fork run in the background while the rest of the workflow proceeds as if the fork were done.

Cross-SDK Confirmation

Same root cause as:

• javascript-sdk#135
• go-sdk#264

The server behavior (empty joinOn → immediate completion) was live-confirmed against Conductor OSS 3.32.0-rc.9 in those audits.

Fix

Require callers to supply the join-on tasks, or expose it as a settable property that must be populated before use:

public DynamicFork(string taskReferenceName, string forkTasksParameter,
    string forkTasksInputsParameter, params WorkflowTask[] joinOn)
{
    this.Join = new JoinTask(taskReferenceName + "_join", joinOn);
    ...
}

For dynamic forks, the tasks are determined at runtime, so the client cannot auto-infer joinOn. The user must explicitly pass the tasks to wait for (typically the dynamic task reference names they configure at workflow design time).