Fix unlink in cluster pipeline (#2562)

Implement unlink() like delete() to make it work when
used in a cluster pipeline.

CHANGES

@@ -1,3 +1,4 @@
+    * Support `.unlink()` in ClusterPipeline
     * Simplify synchronous SocketBuffer state management
     * Fix string cleanse in Redis Graph
     * Make PythonParser resumable in case of error (#2510)

redis/cluster.py

@@ -2136,6 +2136,17 @@ def delete(self, *names):
 
         return self.execute_command("DEL", names[0])
 
+    def unlink(self, *names):
+        """
+        "Unlink a key specified by ``names``"
+        """
+        if len(names) != 1:
+            raise RedisClusterException(
+                "unlinking multiple keys is not implemented in pipeline command"
+            )
+
+        return self.execute_command("UNLINK", names[0])
+
 
 def block_pipeline_command(name: str) -> Callable[..., Any]:
     """

tests/test_cluster.py

@@ -2703,6 +2703,25 @@ def test_multi_delete_unsupported(self, r):
             with pytest.raises(RedisClusterException):
                 pipe.delete("a", "b")
 
+    def test_unlink_single(self, r):
+        """
+        Test a single unlink operation
+        """
+        r["a"] = 1
+        with r.pipeline(transaction=False) as pipe:
+            pipe.unlink("a")
+            assert pipe.execute() == [1]
+
+    def test_multi_unlink_unsupported(self, r):
+        """
+        Test that multi unlink operation is unsupported
+        """
+        with r.pipeline(transaction=False) as pipe:
+            r["a"] = 1
+            r["b"] = 2
+            with pytest.raises(RedisClusterException):
+                pipe.unlink("a", "b")
+
     def test_brpoplpush_disabled(self, r):
         """
         Test that brpoplpush is disabled for ClusterPipeline