fix: Don't rely on URL for initial state

This makes the first render on client side navigation
use the source URL rather than the destination,
which can cause issues if the first state is memoised
or used for some other purposes.

useSearchParams contains the destination values for searchParams,
however this might break in older versions of Next.js (TBC by CI).
In which case this fix might only land on v2.

Author: franky47

Diff for: packages/e2e/cypress/e2e/repro-542.cy.js

@@ -0,0 +1,13 @@
+/// <reference types="cypress" />
+
+it('Reproduction for issue #542', () => {
+  cy.visit('/app/repro-542/a?q=foo&r=bar')
+  cy.contains('#hydration-marker', 'hydrated').should('be.hidden')
+  cy.get('#q').should('have.text', 'foo')
+  cy.get('#r').should('have.text', 'bar')
+  cy.get('a').click()
+  cy.location('search').should('eq', '')
+  cy.get('#q').should('have.text', '')
+  cy.get('#r').should('have.text', '')
+  cy.get('#initial').should('have.text', '{"q":null,"r":null}')
+})

Diff for: packages/e2e/src/app/app/repro-542/a/page.tsx

@@ -0,0 +1,29 @@
+'use client'
+
+import Link from 'next/link'
+import { parseAsString, useQueryState, useQueryStates } from 'nuqs'
+import { Suspense } from 'react'
+
+export default function Page() {
+  return (
+    <Suspense>
+      <Client />
+    </Suspense>
+  )
+}
+
+function Client() {
+  console.log(
+    'rendering page a, url: %s',
+    typeof location !== 'undefined' ? location.href : 'ssr'
+  )
+  const [q] = useQueryState('q')
+  const [{ r }] = useQueryStates({ r: parseAsString })
+  return (
+    <>
+      <div id="q">{q}</div>
+      <div id="r">{r}</div>
+      <Link href="/app/repro-542/b">Go to page B</Link>
+    </>
+  )
+}

Diff for: packages/e2e/src/app/app/repro-542/b/page.tsx

@@ -0,0 +1,32 @@
+'use client'
+
+import { parseAsString, useQueryState, useQueryStates } from 'nuqs'
+import React, { Suspense } from 'react'
+
+export default function Page() {
+  return (
+    <Suspense>
+      <Client />
+    </Suspense>
+  )
+}
+
+function Client() {
+  console.log(
+    'rendering page b, url: %s',
+    typeof location !== 'undefined' ? location.href : 'ssr'
+  )
+  const ref = React.useRef<any>(null)
+  const [q] = useQueryState('q')
+  const [{ r }] = useQueryStates({ r: parseAsString })
+  if (ref.current === null) {
+    ref.current = { q, r }
+  }
+  return (
+    <>
+      <div id="q">{q}</div>
+      <div id="r">{r}</div>
+      <div id="initial">{JSON.stringify(ref.current)}</div>
+    </>
+  )
+}

Diff for: packages/nuqs/src/useQueryState.ts

@@ -227,12 +227,7 @@ export function useQueryState<T = string>(
   const initialSearchParams = useSearchParams()
   const [internalState, setInternalState] = React.useState<T | null>(() => {
     const queueValue = getQueuedValue(key)
-    const urlValue =
-      typeof location !== 'object'
-        ? // SSR
-          initialSearchParams?.get(key) ?? null
-        : // Components mounted after page load must use the current URL value
-          new URLSearchParams(location.search).get(key) ?? null
+    const urlValue = initialSearchParams?.get(key) ?? null
     const value = queueValue ?? urlValue
     return value === null ? null : safeParse(parse, value, key)
   })

Diff for: packages/nuqs/src/useQueryStates.ts

@@ -72,14 +72,9 @@ export function useQueryStates<KeyMap extends UseQueryStatesKeysMap>(
   const router = useRouter()
   // Not reactive, but available on the server and on page load
   const initialSearchParams = useSearchParams()
-  const [internalState, setInternalState] = React.useState<V>(() => {
-    if (typeof location !== 'object') {
-      // SSR
-      return parseMap(keyMap, initialSearchParams ?? new URLSearchParams())
-    }
-    // Components mounted after page load must use the current URL value
-    return parseMap(keyMap, new URLSearchParams(location.search))
-  })
+  const [internalState, setInternalState] = React.useState<V>(() =>
+    parseMap(keyMap, initialSearchParams ?? new URLSearchParams())
+  )
   const stateRef = React.useRef(internalState)
   debug(
     '[nuq+ `%s`] render - state: %O, iSP: %s',