Fix TcpFakeServer EVALSHA NOSCRIPT error handling

- Add NOSCRIPT prefix to NoScriptError messages in TCP protocol
- Add test for EVALSHA with missing script

Author: oliverhaas

fakeredis/_tcp_server.py

@@ -5,6 +5,7 @@
 from socketserver import ThreadingTCPServer, StreamRequestHandler
 from typing import Dict, Tuple, Any, Union
 
+import redis.exceptions
 from redis.lock import Lock
 
 from fakeredis import FakeRedis
@@ -84,7 +85,11 @@ def dump(self, value: Any, dump_bulk: bool = False) -> None:
         elif value is None:
             self.writer.write("$-1\r\n".encode())
         elif isinstance(value, Exception):
-            self.writer.write(f"-{value.args[0]}\r\n".encode())
+            if isinstance(value, redis.exceptions.NoScriptError):
+                error_msg = f"NOSCRIPT {value.args[0]}"
+            else:
+                error_msg = value.args[0]
+            self.writer.write(f"-{error_msg}\r\n".encode())
 
 
 class TCPFakeRequestHandler(StreamRequestHandler):

test/test_tcp_server/test_scripting.py

@@ -0,0 +1,30 @@
+import time
+from threading import Thread
+
+import redis
+
+from fakeredis import TcpFakeServer
+from test import testtools
+
+
+@testtools.run_test_if_lupa_installed()
+def test_evalsha_missing_script():
+    """Test that EVALSHA with a non-existent script returns NOSCRIPT error."""
+    server_address = ("127.0.0.1", 19000)
+    server = TcpFakeServer(server_address)
+    t = Thread(target=server.serve_forever, daemon=True)
+    t.start()
+    time.sleep(0.1)
+
+    with redis.Redis(host=server_address[0], port=server_address[1]) as r:
+        fake_sha = "0" * 40  # Non-existent script/hash
+        try:
+            r.evalsha(fake_sha, 0)
+            assert False, "Expected NoScriptError"
+        except redis.exceptions.NoScriptError:
+            # Success - the server correctly sent NOSCRIPT error and redis-py recognized it
+            pass
+
+    server.server_close()
+    server.shutdown()
+    t.join()