fix: Update useQueryStates state cache when syncing useSearchParams (#776)

This fixes an issue where `<Link>` navigation (or external updates of the URL) kept an internal stale state ref and reused it when updating other search params.

Author: franky47

packages/e2e/next/cypress/e2e/repro-774.cy.js

@@ -0,0 +1,17 @@
+/// <reference types="cypress" />
+
+describe('repro-774', () => {
+  it('updates internal state on navigation', () => {
+    cy.visit('/app/repro-774')
+    cy.contains('#hydration-marker', 'hydrated').should('be.hidden')
+    cy.get('#trigger-a').click()
+    cy.get('#value-a').should('have.text', 'a')
+    cy.get('#value-b').should('be.empty')
+    cy.get('#link').click()
+    cy.get('#value-a').should('be.empty')
+    cy.get('#value-b').should('be.empty')
+    cy.get('#trigger-b').click()
+    cy.get('#value-a').should('be.empty')
+    cy.get('#value-b').should('have.text', 'b')
+  })
+})

packages/e2e/next/src/app/app/repro-774/page.tsx

@@ -0,0 +1,41 @@
+'use client'
+
+import Link from 'next/link'
+import { parseAsString, useQueryStates } from 'nuqs'
+import { Suspense } from 'react'
+
+export default function Home() {
+  return (
+    <>
+      <nav>
+        <Link id="link" href="/app/repro-774">
+          Reset
+        </Link>
+      </nav>
+      <Suspense>
+        <Client />
+      </Suspense>
+    </>
+  )
+}
+
+const searchParams = {
+  a: parseAsString.withDefault(''),
+  b: parseAsString.withDefault('')
+}
+
+function Client() {
+  const [{ a, b }, setSearchParams] = useQueryStates(searchParams)
+  return (
+    <>
+      <button onClick={() => setSearchParams({ a: 'a' })} id="trigger-a">
+        Set A
+      </button>
+      <button onClick={() => setSearchParams({ b: 'b' })} id="trigger-b">
+        Set B
+      </button>
+      <span id="value-a">{a}</span>
+      <span id="value-b">{b}</span>
+    </>
+  )
+}

packages/nuqs/src/useQueryStates.ts

@@ -133,6 +133,7 @@ export function useQueryStates<KeyMap extends UseQueryStatesKeysMap>(
       queryRef.current,
       stateRef.current
     )
+    stateRef.current = state
     setInternalState(state)
   }, [
     Object.values(resolvedUrlKeys)
@@ -274,7 +275,7 @@ function parseMap<KeyMap extends UseQueryStatesKeysMap>(
   cachedQuery?: Record<string, string | null>,
   cachedState?: NullableValues<KeyMap>
 ): NullableValues<KeyMap> {
-  return Object.keys(keyMap).reduce((obj, stateKey) => {
+  return Object.keys(keyMap).reduce((out, stateKey) => {
     const urlKey = urlKeys?.[stateKey] ?? stateKey
     const { parse } = keyMap[stateKey]!
     const queuedQuery = getQueuedValue(urlKey)
@@ -283,15 +284,15 @@ function parseMap<KeyMap extends UseQueryStatesKeysMap>(
         ? (searchParams?.get(urlKey) ?? null)
         : queuedQuery
     if (cachedQuery && cachedState && cachedQuery[urlKey] === query) {
-      obj[stateKey as keyof KeyMap] = cachedState[stateKey] ?? null
-      return obj
+      out[stateKey as keyof KeyMap] = cachedState[stateKey] ?? null
+      return out
     }
     const value = query === null ? null : safeParse(parse, query, stateKey)
-    obj[stateKey as keyof KeyMap] = value ?? null
+    out[stateKey as keyof KeyMap] = value ?? null
     if (cachedQuery) {
       cachedQuery[urlKey] = query
     }
-    return obj
+    return out
   }, {} as NullableValues<KeyMap>)
 }