Function _ensure_scope_stack

python/nemo_relay/scope.py:43–69

Ensure the current context's scope stack is active on the Rust thread-local. Three cases: 1. **ContextVar is set** (normal async tasks, or after ``push_node_scope`` installed a branch stack): always re-sync it to the Rust thread-local. This is critical because concurrent asyn

()

def _ensure_scope_stack() -> None:
    """Ensure the current context's scope stack is active on the Rust thread-local.

    Three cases:

    1. **ContextVar is set** (normal async tasks, or after ``push_node_scope``
       installed a branch stack): always re-sync it to the Rust thread-local.
       This is critical because concurrent async tasks share a single OS thread
       and the thread-local may have been overwritten by another task.
    2. **ContextVar is empty but thread-local is set** (worker threads that
       called ``set_thread_scope_stack``): keep the thread-local as-is.
    3. **Neither is set**: create a new scope stack via ``get_scope_stack()``.
    """
    import nemo_relay

    # Case 1: ContextVar owns a stack — re-sync it to the Rust thread-local.
    stack = nemo_relay._scope_stack_var.get(None)
    if stack is not None:
        nemo_relay._sync_thread_scope_stack(stack)
        return

    # Case 2: Worker thread with explicit set_thread_scope_stack — don't clobber.
    if nemo_relay._native_scope_stack_active():
        return

    # Case 3: Fresh context — create and register a new stack.
    nemo_relay.get_scope_stack()


def get_handle() -> ScopeHandle: