const PUSH_STATE_KEYS = [
  "pushStatus",
  "watchExpirationMs",
  "pubsubTopic",
  "lastPushError"
];
function preservePushState(previous, next) {
  const prev = previous && typeof previous === "object" && !Array.isArray(previous) ? previous : {};
  const merged = { ...next };
  for (const key of PUSH_STATE_KEYS) {
    if (!(key in merged) && key in prev) merged[key] = prev[key];
  }
  return merged;
}
export {
  PUSH_STATE_KEYS,
  preservePushState
};
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