Revert "Avoid unnecessary router state changes"

packages/next/shared/lib/router/router.ts

@@ -81,37 +81,6 @@ function buildCancellationError() {
   })
 }
 
-function compareRouterStates(a: Router['state'], b: Router['state']) {
-  const stateKeys = Object.keys(a)
-  if (stateKeys.length !== Object.keys(b).length) return false
-
-  for (let i = stateKeys.length; i--; ) {
-    const key = stateKeys[i]
-    if (key === 'query') {
-      const queryKeys = Object.keys(a.query)
-      if (queryKeys.length !== Object.keys(b.query).length) {
-        return false
-      }
-      for (let j = queryKeys.length; j--; ) {
-        const queryKey = queryKeys[j]
-        if (
-          !b.query.hasOwnProperty(queryKey) ||
-          a.query[queryKey] !== b.query[queryKey]
-        ) {
-          return false
-        }
-      }
-    } else if (
-      !b.hasOwnProperty(key) ||
-      a[key as keyof Router['state']] !== b[key as keyof Router['state']]
-    ) {
-      return false
-    }
-  }
-
-  return true
-}
-
 /**
  * Detects whether a given url is routable by the Next.js router (browser only).
  */
@@ -1343,47 +1312,38 @@ export default class Router implements BaseRouter {
       const shouldScroll = options.scroll ?? !isValidShallowRoute
       const resetScroll = shouldScroll ? { x: 0, y: 0 } : null
 
-      const nextScroll = forcedScroll ?? resetScroll
-      const mergedNextState = {
-        ...nextState,
-        route,
-        pathname,
-        query,
-        asPath: cleanedAs,
-        isFallback: false,
-      }
-
-      // for query updates we can skip it if the state is unchanged and we don't
-      // need to scroll
-      // https://github.com/vercel/next.js/issues/37139
-      const canSkipUpdating =
-        (options as any)._h &&
-        !nextScroll &&
-        compareRouterStates(mergedNextState, this.state)
-
-      if (!canSkipUpdating) {
-        await this.set(mergedNextState, routeInfo, nextScroll).catch((e) => {
-          if (e.cancelled) error = error || e
-          else throw e
-        })
+      await this.set(
+        {
+          ...nextState,
+          route,
+          pathname,
+          query,
+          asPath: cleanedAs,
+          isFallback: false,
+        },
+        routeInfo,
+        forcedScroll ?? resetScroll
+      ).catch((e) => {
+        if (e.cancelled) error = error || e
+        else throw e
+      })
 
-        if (error) {
-          Router.events.emit('routeChangeError', error, cleanedAs, routeProps)
-          throw error
-        }
+      if (error) {
+        Router.events.emit('routeChangeError', error, cleanedAs, routeProps)
+        throw error
+      }
 
-        if (process.env.__NEXT_I18N_SUPPORT) {
-          if (nextState.locale) {
-            document.documentElement.lang = nextState.locale
-          }
+      if (process.env.__NEXT_I18N_SUPPORT) {
+        if (nextState.locale) {
+          document.documentElement.lang = nextState.locale
         }
-        Router.events.emit('routeChangeComplete', as, routeProps)
+      }
+      Router.events.emit('routeChangeComplete', as, routeProps)
 
-        // A hash mark # is the optional last part of a URL
-        const hashRegex = /#.+$/
-        if (shouldScroll && hashRegex.test(as)) {
-          this.scrollToHash(as)
-        }
+      // A hash mark # is the optional last part of a URL
+      const hashRegex = /#.+$/
+      if (shouldScroll && hashRegex.test(as)) {
+        this.scrollToHash(as)
       }
 
       return true