StackExchange.Redis #1294 Reproduction

Program.cs

using StackExchange.Redis;

void WriteToRedis(IDatabase db, string key, int len, int fillByte)
{
    byte[] value = Enumerable.Repeat((byte) fillByte, len).ToArray();
    Console.WriteLine($"\n\nWriting key '{key}', length {len}...");
    try
    {
        db.StringSet(key, value);
    }
    catch (Exception ex)
    {
        Console.WriteLine($"WriteToRedis caught exception: {ex.Message}");
    }
}

ConnectionMultiplexer redis = ConnectionMultiplexer.Connect("localhost");
IDatabase db = redis.GetDatabase();

/* Magic length 555 will simulate an OutOfMemoryException
 * in the middle of writing the value.  The command will fail
 * by timing out after 5000ms
 */
db.KeyDelete("key1");
WriteToRedis(db, "key1", 555, 'x');

/* This command will break protocol encapsulation, and will
 * be partially stored in "key1"
 */
WriteToRedis(db, "key2", 222, 'y');

// Force a reconnect, then print the value of "key1"
redis.Dispose();
redis = ConnectionMultiplexer.Connect("localhost");
db = redis.GetDatabase();

var value = db.StringGet("key1");
Console.WriteLine($"\n\nStored value for key1 was: {value}");

stackexchangeredis-simulated-error.diff

diff --git a/src/StackExchange.Redis/Message.cs b/src/StackExchange.Redis/Message.cs
index c8fdf54f..939c898f 100644
--- a/src/StackExchange.Redis/Message.cs
+++ b/src/StackExchange.Redis/Message.cs
@@ -769,6 +769,7 @@ internal void WriteTo(PhysicalConnection physical)
             }
             catch (Exception ex) when (!(ex is RedisCommandException)) // these have specific meaning; don't wrap
             {
+                Console.WriteLine($"Message.WriteTo caught {ex.Message}");
                 physical?.OnInternalError(ex);
                 Fail(ConnectionFailureType.InternalFailure, ex, null);
             }
diff --git a/src/StackExchange.Redis/PhysicalConnection.cs b/src/StackExchange.Redis/PhysicalConnection.cs
index bbbccf4e..ff93a0ba 100644
--- a/src/StackExchange.Redis/PhysicalConnection.cs
+++ b/src/StackExchange.Redis/PhysicalConnection.cs
@@ -998,7 +998,15 @@ private static void WriteUnifiedSpan(PipeWriter writer, ReadOnlySpan<byte> value
                 int bytes = WriteRaw(span, value.Length, offset: 1);
                 writer.Advance(bytes);
 
-                writer.Write(value);
+                if (value.Length == 555)
+                {
+                    writer.Write(value.Slice(0, 400));
+                    throw new OutOfMemoryException();
+                }
+                else
+                {
+                    writer.Write(value);
+                }
 
                 WriteCrlf(writer);
             }