refactor(router-core): buildLocation can skip decoding the next pathname if we dont encode it in the first place

Author: Sheraff

packages/router-core/src/path.ts

@@ -208,8 +208,10 @@ export function resolvePath({
 interface InterpolatePathOptions {
   path?: string
   params: Record<string, unknown>
-  // Map of encoded chars to decoded chars (e.g. '%40' -> '@') that should remain decoded in path params
+  /** Map of encoded chars to decoded chars (e.g. '%40' -> '@') that should remain decoded in path params */
   decodeCharMap?: Map<string, string>
+  /** whether to encode the interpolated params (defaults: true) */
+  encode?: boolean
 }
 
 type InterPolatePathResult = {
@@ -248,6 +250,7 @@ export function interpolatePath({
   path,
   params,
   decodeCharMap,
+  encode = true,
 }: InterpolatePathOptions): InterPolatePathResult {
   // Tracking if any params are missing in the `params` object
   // when interpolating the path
@@ -298,7 +301,9 @@ export function interpolatePath({
         continue
       }
 
-      const value = encodeParam('_splat', params, decodeCharMap)
+      const value = encode
+        ? encodeParam('_splat', params, decodeCharMap)
+        : params._splat
       joined += '/' + prefix + value + suffix
       continue
     }
@@ -312,7 +317,9 @@ export function interpolatePath({
 
       const prefix = path.substring(start, segment[1])
       const suffix = path.substring(segment[4], end)
-      const value = encodeParam(key, params, decodeCharMap) ?? 'undefined'
+      const value =
+        (encode ? encodeParam(key, params, decodeCharMap) : params[key]) ??
+        'undefined'
       joined += '/' + prefix + value + suffix
       continue
     }
@@ -335,7 +342,8 @@ export function interpolatePath({
 
       usedParams[key] = valueRaw
 
-      const value = encodeParam(key, params, decodeCharMap) ?? ''
+      const value =
+        (encode ? encodeParam(key, params, decodeCharMap) : params[key]) ?? ''
       joined += '/' + prefix + value + suffix
       continue
     }

packages/router-core/src/router.ts

@@ -1184,7 +1184,7 @@ export class RouterCore<
         pathname: decodePath(pathname),
         searchStr,
         search: replaceEqualDeep(previousLocation?.search, parsedSearch) as any,
-        hash: hash.split('#').reverse()[0] ?? '',
+        hash: last(hash.split('#')) ?? '',
         state: replaceEqualDeep(previousLocation?.state, state),
       }
     }
@@ -1681,13 +1681,11 @@ export class RouterCore<
         ? // Use the original template path for interpolation
           // This preserves the original parameter syntax including optional parameters
           nextTo
-        : decodePath(
-            interpolatePath({
-              path: nextTo,
-              params: nextParams,
-              decodeCharMap: this.pathParamsDecodeCharMap,
-            }).interpolatedPath,
-          )
+        : interpolatePath({
+            path: nextTo,
+            params: nextParams,
+            encode: false,
+          }).interpolatedPath
 
       // Resolve the next search
       let nextSearch = fromSearch