Method traverse

packages/graph/src/Steps.ts:3945–3984

(
    source: GraphSource<any>,
    input: Iterable<unknown>,
    context?: QueryContext,
  )

  }

  public *traverse(
    source: GraphSource<any>,
    input: Iterable<unknown>,
    context?: QueryContext,
  ): IterableIterator<unknown> {
    const { directions } = this.config;
    const sorted = [...input].sort((a, b) => {
      for (const { key, expression, direction, nulls } of directions) {
        const aValue = resolveOrderValue(a, key, expression, context);
        const bValue = resolveOrderValue(b, key, expression, context);

        // Handle null values according to nulls ordering
        const aIsNull = aValue === null || aValue === undefined;
        const bIsNull = bValue === null || bValue === undefined;

        if (aIsNull && bIsNull) {
          continue; // Both null, check next sort key
        }

        if (aIsNull || bIsNull) {
          // Determine default nulls ordering based on direction if not specified
          // Default: NULLS LAST for ASC, NULLS FIRST for DESC (matches PostgreSQL behavior)
          const effectiveNulls = nulls ?? (direction === "asc" ? "last" : "first");

          if (aIsNull) {
            return effectiveNulls === "first" ? -1 : 1;
          } else {
            return effectiveNulls === "first" ? 1 : -1;
          }
        }

        const result = compare(aValue, bValue);
        if (result !== 0) {
          return direction === "asc" ? result : -result;
        }
      }
      return 0;
    });
    yield* sorted;
  }

  public override clone(partial?: Partial<OrderStepConfig>) {
    return new OrderStep({