In useSWRInfinite, the pageIndex always ends with 0 when console.log

[devjiwonchoi]

I am aware of swr revalidating the first page, related issue #1401. Is it also an expected behavior for the pageIndex?
Note that I've tried revalidateFirstPage: false

Background

• Next.js App Router (route.ts)
• useSWRInfinite
• Notion API

route.ts

Increments, but ends up with 0, eventually fails to paginate.

Client Side Fetch to route api

// /app/blog/page.tsx

'use client'
import useSWRInfinite from 'swr/infinite'

const fetcher = (url: string) => fetch(url).then((res) => res.json())
const getKey = (pageIndex: number, previousPageData: any) => {
  if (previousPageData && !previousPageData.length) return null

  console.log(pageIndex) // ------> here

  return `/api/blog/posts?pageIndex=${pageIndex + 1}`
}

export default function Blog() {
  const { data, isLoading, isValidating, size, setSize } = useSWRInfinite(
    getKey,
    fetcher
  )
  // ...rest of the codes
  return (
    // ...rest of the codes
  )
}

// Browser Console

0
0
1
2
3
0 ------> returns 0 at last