Function hydrate

packages/next/src/client/app-index.tsx:349–428

(
  instrumentationHooks: ClientInstrumentationHooks | null,
  assetPrefix: string
)

}

export async function hydrate(
  instrumentationHooks: ClientInstrumentationHooks | null,
  assetPrefix: string
) {
  let staticIndicatorState: StaticIndicatorState | undefined
  let webSocket: WebSocket | undefined

  if (process.env.__NEXT_DEV_SERVER) {
    const { createWebSocket } =
      require('./dev/hot-reloader/app/web-socket') as typeof import('./dev/hot-reloader/app/web-socket')

    staticIndicatorState = { pathname: null, appIsrManifest: null }
    webSocket = createWebSocket(assetPrefix, staticIndicatorState)
  }
  const initialRSCPayload = await initialServerResponse

  // setNavigationBuildId should be called only once, during JS initialization
  // and before any components have hydrated.
  if (initialRSCPayload.b) {
    setNavigationBuildId(initialRSCPayload.b!)
  } else {
    setNavigationBuildId(getDeploymentId()!)
  }

  const initialTimestamp = Date.now()
  const actionQueue: AppRouterActionQueue = createMutableActionQueue(
    createInitialRouterState({
      navigatedAt: initialTimestamp,
      initialRSCPayload,
      initialFlightStreamForCache,
      location: window.location,
    }),
    instrumentationHooks
  )

  const reactEl = (
    <StrictModeIfEnabled>
      <HeadManagerContext.Provider value={{ appDir: true }}>
        <Root>
          <ServerRoot
            initialRSCPayload={initialRSCPayload}
            actionQueue={actionQueue}
            webSocket={webSocket}
            staticIndicatorState={staticIndicatorState}
          />
        </Root>
      </HeadManagerContext.Provider>
    </StrictModeIfEnabled>
  )

  if (document.documentElement.id === '__next_error__') {
    let element = reactEl
    // Server rendering failed, fall back to client-side rendering
    if (process.env.NODE_ENV !== 'production') {
      const { RootLevelDevOverlayElement } =
        require('../next-devtools/userspace/app/client-entry') as typeof import('../next-devtools/userspace/app/client-entry')

      // Note this won't cause hydration mismatch because we are doing CSR w/o hydration