Function flushPartialBoundary

packages/react-server/src/ReactFizzServer.js:5905–5946

(
  request: Request,
  destination: Destination,
  boundary: SuspenseBoundary,
)

}

function flushPartialBoundary(
  request: Request,
  destination: Destination,
  boundary: SuspenseBoundary,
): boolean {
  flushedByteSize = boundary.byteSize; // Start counting bytes
  const completedSegments = boundary.completedSegments;
  let i = 0;
  for (; i < completedSegments.length; i++) {
    const segment = completedSegments[i];
    if (
      !flushPartiallyCompletedSegment(request, destination, boundary, segment)
    ) {
      i++;
      completedSegments.splice(0, i);
      // Only write as much as the buffer wants. Something higher priority
      // might want to write later.
      return false;
    }
  }
  completedSegments.splice(0, i);

  const row = boundary.row;
  if (row !== null && row.together && boundary.pendingTasks === 1) {
    // "together" rows are blocked on their own boundaries.
    // We have now flushed all the boundary's segments as partials.
    // We can now unblock it from blocking the row that will eventually
    // unblock the boundary itself which can issue its complete instruction.
    // TODO: Ideally the complete instruction would be in a single <script> tag.
    if (row.pendingTasks === 1) {
      unblockSuspenseListRow(request, row, row.hoistables);
    } else {
      row.pendingTasks--;
    }
  }

  return writeHoistablesForBoundary(
    destination,
    boundary.contentState,
    request.renderState,
  );
}

function flushPartiallyCompletedSegment(
  request: Request,