Fix redis#2581 UnixDomainSocketConnection' object has no attribute '_…

…command_packer' .

Apparently there is no end-to-end tests for Unix sockets
 so automation didn't catch it.  I assume that setting up
domain sockets reliably  in dockerized environment is not
very trivial.
Added test for pack_command specifically.

redis/connection.py

@@ -1153,6 +1153,7 @@ def __init__(
         retry=None,
         redis_connect_func=None,
         credential_provider: Optional[CredentialProvider] = None,
+        command_packer=None,
     ):
         """
         Initialize a new UnixDomainSocketConnection.
@@ -1202,6 +1203,7 @@ def __init__(
         self.set_parser(parser_class)
         self._connect_callbacks = []
         self._buffer_cutoff = 6000
+        self._command_packer = self._construct_command_packer(command_packer)
 
     def repr_pieces(self):
         pieces = [("path", self.path), ("db", self.db)]

tests/test_connection.py

@@ -7,7 +7,13 @@
 
 import redis
 from redis.backoff import NoBackoff
-from redis.connection import Connection, HiredisParser, PythonParser
+from redis.connection import (
+    Connection,
+    HiredisParser,
+    PythonParser,
+    SSLConnection,
+    UnixDomainSocketConnection,
+)
 from redis.exceptions import ConnectionError, InvalidResponse, TimeoutError
 from redis.retry import Retry
 from redis.utils import HIREDIS_AVAILABLE
@@ -163,3 +169,41 @@ def test_connection_parse_response_resume(r: redis.Redis, parser_class):
         pytest.fail("didn't receive a response")
     assert response
     assert i > 0
+
+
+@pytest.mark.onlynoncluster
+@pytest.mark.parametrize(
+    "Class",
+    [
+        Connection,
+        SSLConnection,
+        UnixDomainSocketConnection,
+    ],
+)
+def test_pack_command(Class):
+    """
+    This test verifies that the pack_command works
+    on all supported connections. #2581
+    """
+    cmd = (
+        "HSET",
+        "foo",
+        "key",
+        "value1",
+        b"key_b",
+        b"bytes str",
+        "key_mv",
+        memoryview(b"bytes str"),
+        b"key_i",
+        67,
+        "key_f",
+        3.14159265359,
+    )
+    expected = (
+        b"*12\r\n$4\r\nHSET\r\n$3\r\nfoo\r\n$3\r\nkey\r\n$6\r\nvalue1\r\n"
+        b"$5\r\nkey_b\r\n$9\r\nbytes str\r\n$6\r\nkey_mv\r\n$9\r\n"
+        b"bytes str\r\n$5\r\nkey_i\r\n$2\r\n67\r\n$5\r\nkey_f\r\n$13\r\n"
+        b"3.14159265359\r\n"
+    )
+
+    assert Class().pack_command(*cmd)[0] == expected