fix incorrect debug assertion in HGETEX; no impact to release build (#2999)

* fix incorrect debug assertion in HGETEX; no impact to release build

* add release note

Author: mgravell

docs/ReleaseNotes.md

@@ -6,6 +6,10 @@ Current package versions:
 | ------------ | ----------------- | ----- |
 | [![StackExchange.Redis](https://img.shields.io/nuget/v/StackExchange.Redis.svg)](https://www.nuget.org/packages/StackExchange.Redis/) | [![StackExchange.Redis](https://img.shields.io/nuget/vpre/StackExchange.Redis.svg)](https://www.nuget.org/packages/StackExchange.Redis/) | [![StackExchange.Redis MyGet](https://img.shields.io/myget/stackoverflow/vpre/StackExchange.Redis.svg)](https://www.myget.org/feed/stackoverflow/package/nuget/StackExchange.Redis) |
 
+## unreleased
+
+- Fix incorrect debug assertion in `HGETEX` (no impact to release library) ([#2999 by mgravell](https://github.com/StackExchange/StackExchange.Redis/pull/2999))
+
 ## 2.10.1
 
 - Support Redis 8.4 CAS/CAD operations (`DIGEST`, and the `IFEQ`, `IFNE`, `IFDEQ`, `IFDNE` modifiers on `SET` / `DEL`)

src/StackExchange.Redis/RedisDatabase.cs

@@ -507,10 +507,9 @@ private Message HashFieldGetAndSetExpiryMessage(in RedisKey key, RedisValue[] ha
                 return HashFieldGetAndSetExpiryMessage(key, in hashFields[0], expiry, flags);
             }
 
-            // precision, time, FIELDS, hashFields.Length
+            // precision, time, FIELDS, hashFields.Length, {N x fields}
             int extraTokens = expiry.TokenCount + 2;
-
-            RedisValue[] values = new RedisValue[expiry.TokenCount + 2 + hashFields.Length];
+            RedisValue[] values = new RedisValue[extraTokens + hashFields.Length];
 
             int index = 0;
             // add PERSIST or expiry values
@@ -528,7 +527,7 @@ private Message HashFieldGetAndSetExpiryMessage(in RedisKey key, RedisValue[] ha
             values[index++] = RedisLiterals.FIELDS;
             values[index++] = hashFields.Length;
             // check we've added everything we expected to
-            Debug.Assert(index == extraTokens + hashFields.Length);
+            Debug.Assert(index == extraTokens, $"token mismatch: {index} vs {extraTokens}");
 
             // Add hash fields to the array
             hashFields.AsSpan().CopyTo(values.AsSpan(index));