refactor(router-core): Avoid creating empty objects when not necessary (#4923)

`undefined` is allowed as the parameter of the `...` spread operator. It
is not necessary to create an empty object `{}` as a fallback.

Creating objects incurs more work by the garbage collector, so
minimizing how many are created if a performance improvement.

Author: Sheraff

packages/router-core/src/Matches.ts

@@ -150,7 +150,7 @@ export interface RouteMatch<
   }
   loaderData?: TLoaderData
   /** @internal */
-  __routeContext: Record<string, unknown>
+  __routeContext?: Record<string, unknown>
   /** @internal */
   __beforeLoadContext?: Record<string, unknown>
   context: TAllContext

packages/router-core/src/router.ts

@@ -1146,8 +1146,8 @@ export class RouterCore<
       const parentMatchId = parentMatch?.id
 
       const parentContext = !parentMatchId
-        ? ((this.options.context as any) ?? {})
-        : (parentMatch.context ?? this.options.context ?? {})
+        ? ((this.options.context as any) ?? undefined)
+        : (parentMatch.context ?? this.options.context ?? undefined)
 
       return parentContext
     }
@@ -1169,12 +1169,12 @@ export class RouterCore<
       ] = (() => {
         // Validate the search params and stabilize them
         const parentSearch = parentMatch?.search ?? next.search
-        const parentStrictSearch = parentMatch?._strictSearch ?? {}
+        const parentStrictSearch = parentMatch?._strictSearch ?? undefined
 
         try {
           const strictSearch =
             validateSearch(route.options.validateSearch, { ...parentSearch }) ??
-            {}
+            undefined
 
           return [
             {
@@ -1284,7 +1284,7 @@ export class RouterCore<
           isFetching: false,
           error: undefined,
           paramsError: parseErrors[index],
-          __routeContext: {},
+          __routeContext: undefined,
           _nonReactive: {
             loadPromise: createControlledPromise(),
           },
@@ -1337,22 +1337,25 @@ export class RouterCore<
         const parentContext = getParentContext(parentMatch)
 
         // Update the match's context
-        const contextFnContext: RouteContextOptions<any, any, any, any> = {
-          deps: match.loaderDeps,
-          params: match.params,
-          context: parentContext,
-          location: next,
-          navigate: (opts: any) =>
-            this.navigate({ ...opts, _fromLocation: next }),
-          buildLocation: this.buildLocation,
-          cause: match.cause,
-          abortController: match.abortController,
-          preload: !!match.preload,
-          matches,
-        }
 
-        // Get the route context
-        match.__routeContext = route.options.context?.(contextFnContext) ?? {}
+        if (route.options.context) {
+          const contextFnContext: RouteContextOptions<any, any, any, any> = {
+            deps: match.loaderDeps,
+            params: match.params,
+            context: parentContext ?? {},
+            location: next,
+            navigate: (opts: any) =>
+              this.navigate({ ...opts, _fromLocation: next }),
+            buildLocation: this.buildLocation,
+            cause: match.cause,
+            abortController: match.abortController,
+            preload: !!match.preload,
+            matches,
+          }
+          // Get the route context
+          match.__routeContext =
+            route.options.context(contextFnContext) ?? undefined
+        }
 
         match.context = {
           ...parentContext,
@@ -1486,13 +1489,9 @@ export class RouterCore<
         parseCache: this.parsePathnameCache,
       }).interpolatedPath
 
-      const destRoutes = this.matchRoutes(
-        interpolatedNextTo,
-        {},
-        {
-          _buildLocation: true,
-        },
-      ).map((d) => this.looseRoutesById[d.routeId]!)
+      const destRoutes = this.matchRoutes(interpolatedNextTo, undefined, {
+        _buildLocation: true,
+      }).map((d) => this.looseRoutesById[d.routeId]!)
 
       // If there are any params, we need to stringify them
       if (Object.keys(nextParams).length > 0) {
@@ -2378,7 +2377,7 @@ export class RouterCore<
                   const abortController = new AbortController()
 
                   const parentMatchContext =
-                    parentMatch?.context ?? this.options.context ?? {}
+                    parentMatch?.context ?? this.options.context ?? undefined
 
                   updateMatch(matchId, (prev) => ({
                     ...prev,
@@ -2787,7 +2786,7 @@ export class RouterCore<
           invalid: true,
           ...(opts?.forcePending || d.status === 'error'
             ? ({ status: 'pending', error: undefined } as const)
-            : {}),
+            : undefined),
         }
       }
       return d
@@ -3558,7 +3557,8 @@ function applySearchMiddleware({
             try {
               const validatedSearch = {
                 ...result,
-                ...(validateSearch(route.options.validateSearch, result) ?? {}),
+                ...(validateSearch(route.options.validateSearch, result) ??
+                  undefined),
               }
               return validatedSearch
             } catch {

packages/router-core/src/ssr/ssr-client.ts

@@ -139,24 +139,27 @@ export async function hydrate(router: AnyRouter): Promise<any> {
       const route = router.looseRoutesById[match.routeId]!
 
       const parentMatch = router.state.matches[match.index - 1]
-      const parentContext = parentMatch?.context ?? router.options.context ?? {}
+      const parentContext = parentMatch?.context ?? router.options.context
 
       // `context()` was already executed by `matchRoutes`, however route context was not yet fully reconstructed
       // so run it again and merge route context
-      const contextFnContext: RouteContextOptions<any, any, any, any> = {
-        deps: match.loaderDeps,
-        params: match.params,
-        context: parentContext,
-        location: router.state.location,
-        navigate: (opts: any) =>
-          router.navigate({ ...opts, _fromLocation: router.state.location }),
-        buildLocation: router.buildLocation,
-        cause: match.cause,
-        abortController: match.abortController,
-        preload: false,
-        matches,
+      if (route.options.context) {
+        const contextFnContext: RouteContextOptions<any, any, any, any> = {
+          deps: match.loaderDeps,
+          params: match.params,
+          context: parentContext ?? {},
+          location: router.state.location,
+          navigate: (opts: any) =>
+            router.navigate({ ...opts, _fromLocation: router.state.location }),
+          buildLocation: router.buildLocation,
+          cause: match.cause,
+          abortController: match.abortController,
+          preload: false,
+          matches,
+        }
+        match.__routeContext =
+          route.options.context(contextFnContext) ?? undefined
       }
-      match.__routeContext = route.options.context?.(contextFnContext) ?? {}
 
       match.context = {
         ...parentContext,