ChildWorkflowOptions missing WorkflowIDConflictPolicy (only StartWorkflowOptions has it)

[autocracy]

Summary

WorkflowIDConflictPolicy was added to StartWorkflowOptions in v1.26.0, but ChildWorkflowOptions has never been updated to include an equivalent field. This creates an asymmetry: callers who want WORKFLOW_ID_CONFLICT_POLICY_TERMINATE_EXISTING semantics for child workflows have no supported way to express it.

Current behavior

ChildWorkflowOptions only exposes WorkflowIDReusePolicy. The deprecation of WORKFLOW_ID_REUSE_POLICY_TERMINATE_IF_RUNNING was paired with the introduction of WorkflowIDConflictPolicy on the client-start path (StartWorkflowOptions), but the child-workflow execution path was not updated to match.

// Works fine — conflict policy available
opts := client.StartWorkflowOptions{
    WorkflowIDConflictPolicy: enumspb.WORKFLOW_ID_CONFLICT_POLICY_TERMINATE_EXISTING,
}

// No equivalent — must use the deprecated reuse policy instead
childOpts := workflow.ChildWorkflowOptions{
    WorkflowIDReusePolicy: enumspb.WORKFLOW_ID_REUSE_POLICY_TERMINATE_IF_RUNNING, // deprecated, but only option
}

Expected behavior

ChildWorkflowOptions should include a WorkflowIDConflictPolicy field, mirroring the field already present in StartWorkflowOptions.

Impact

Users who follow the migration guidance to replace WORKFLOW_ID_REUSE_POLICY_TERMINATE_IF_RUNNING with WORKFLOW_ID_CONFLICT_POLICY_TERMINATE_EXISTING can do so for top-level workflow starts but are forced to suppress deprecation lints and continue using the deprecated reuse policy for child workflows. There is no non-deprecated path to achieve terminate-existing semantics in child workflow execution.

SDK version

Confirmed in v1.41.1. The asymmetry has existed since at least v1.26.0 when WorkflowIDConflictPolicy was introduced.

[yuandrew]

Thank you for raising the issue, this is an existing feature request. Unfortunately, the SDK is blocked from supporting this by pending server work, temporalio/temporal#6799. I'm also linking this to the parent features issue temporalio/features#558