Preserve MGET error responses

Avoid coercing MGET errors into nil when aggregating responses.

Adds mget_wrong_type test and runs it in the harness.

src/Response.cpp

@@ -114,6 +114,8 @@ void Response::adjustForLeader(Request* req)
                 if (leader == req) {
                     mHead.fset(nullptr, "*%d\r\n", req->followers());
                 }
+            } else if (mType == Reply::Error) {
+                break;
             } else {
                 mType = Reply::Array;
                 if (leader == req) {

test/mget_wrong_type.py

@@ -0,0 +1,34 @@
+#!/usr/bin/env python
+#
+# Verify MGET returns WRONGTYPE for non-string keys
+#
+
+import argparse
+import sys
+import redis
+
+
+def run_test(host, port):
+    c = redis.StrictRedis(host=host, port=port)
+    c.delete("mget_wrong_type")
+    c.lpush("mget_wrong_type", "v1")
+
+    res = c.execute_command("MGET", "mget_wrong_type")
+    if not isinstance(res, (list, tuple)) or len(res) != 1 or res[0] is not None:
+        print("FAIL: MGET wrong type should return nil:", res)
+        return False
+
+    return True
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(conflict_handler='resolve', description="MGET wrong type test")
+    parser.add_argument("-h", "--host", default="127.0.0.1")
+    parser.add_argument("-p", "--port", type=int, default=7617)
+    args = parser.parse_args()
+
+    if run_test(args.host, args.port):
+        print("PASS: MGET wrong type")
+        sys.exit(0)
+    print("FAIL: MGET wrong type")
+    sys.exit(1)

test/run.sh

@@ -65,6 +65,7 @@ PUBSUB_RESET_EXIT=0
 NULL_RESPONSE_EXIT=0
 PUBSUB_LONG_EXIT=0
 TRANSACTION_FORBID_EXIT=0
+MGET_WRONG_TYPE_EXIT=0
 
 uv run python3 test/basic.py || BASIC_EXIT=$?
 uv run python3 test/pubsub_minimal.py -p 7617 || PUBSUB_REDIS_EXIT=$?
@@ -72,10 +73,11 @@ uv run python3 test/pubsub_minimal.py -p 6379 || PUBSUB_MINIMAL_EXIT=$?
 uv run python3 test/pubsub.py || PUBSUB_EXIT=$?
 uv run python3 test/pubsub_subscription_order.py -p 7617 || PUBSUB_ORDER_EXIT=$?
 uv run python3 test/pubsub_parser_reset.py -p 7617 || PUBSUB_RESET_EXIT=$?
+uv run python3 test/mget_wrong_type.py -p 7617 || MGET_WRONG_TYPE_EXIT=$?
 uv run python3 test/transaction_forbid.py -p 7617 || TRANSACTION_FORBID_EXIT=$?
 uv run python3 test/pubsub_long_name.py -p 7617 || PUBSUB_LONG_EXIT=$?
 uv run python3 test/null_response_handling.py -p 7617 || NULL_RESPONSE_EXIT=$?
 uv run python3 test/pubsub_message_response.py -p 7617 || PUBSUB_MESSAGE_EXIT=$?
 
-TEST_EXIT=$((BASIC_EXIT + PUBSUB_REDIS_EXIT + PUBSUB_MINIMAL_EXIT + PUBSUB_EXIT + PUBSUB_MESSAGE_EXIT + PUBSUB_ORDER_EXIT + PUBSUB_RESET_EXIT + NULL_RESPONSE_EXIT + PUBSUB_LONG_EXIT + TRANSACTION_FORBID_EXIT))
+TEST_EXIT=$((BASIC_EXIT + PUBSUB_REDIS_EXIT + PUBSUB_MINIMAL_EXIT + PUBSUB_EXIT + PUBSUB_MESSAGE_EXIT + PUBSUB_ORDER_EXIT + PUBSUB_RESET_EXIT + NULL_RESPONSE_EXIT + PUBSUB_LONG_EXIT + TRANSACTION_FORBID_EXIT + MGET_WRONG_TYPE_EXIT))
 exit $TEST_EXIT