Add support for EVALSHA_RO (#1863)

* add evalsha-ro

* fix pr comment

* add type hints

* add type hints

Author: dvora-h

redis/commands/core.py

@@ -3947,7 +3947,12 @@ def eval_ro(self, script: str, numkeys: int, *keys_and_args: list) -> str:
         """
         return self._eval("EVAL_RO", script, numkeys, *keys_and_args)
 
-    def evalsha(self, sha, numkeys, *keys_and_args):
+    def _evalsha(
+        self, command: str, sha: str, numkeys: int, *keys_and_args: list
+    ) -> str:
+        return self.execute_command(command, sha, numkeys, *keys_and_args)
+
+    def evalsha(self, sha: str, numkeys: int, *keys_and_args: list) -> str:
         """
         Use the ``sha`` to execute a Lua script already registered via EVAL
         or SCRIPT LOAD. Specify the ``numkeys`` the script will touch and the
@@ -3959,7 +3964,20 @@ def evalsha(self, sha, numkeys, *keys_and_args):
 
         For more information check  https://redis.io/commands/evalsha
         """
-        return self.execute_command("EVALSHA", sha, numkeys, *keys_and_args)
+        return self._evalsha("EVALSHA", sha, numkeys, *keys_and_args)
+
+    def evalsha_ro(self, sha: str, numkeys: int, *keys_and_args: list) -> str:
+        """
+        The read-only variant of the EVALSHA command
+
+        Use the ``sha`` to execute a read-only Lua script already registered via EVAL
+        or SCRIPT LOAD. Specify the ``numkeys`` the script will touch and the
+        key names and argument values in ``keys_and_args``. Returns the result
+        of the script.
+
+        For more information check  https://redis.io/commands/evalsha_ro
+        """
+        return self._evalsha("EVALSHA_RO", sha, numkeys, *keys_and_args)
 
     def script_exists(self, *args):
         """

tests/test_scripting.py

@@ -74,6 +74,15 @@ def test_evalsha(self, r):
         # 2 * 3 == 6
         assert r.evalsha(sha, 1, "a", 3) == 6
 
+    # @skip_if_server_version_lt("7.0.0") turn on after redis 7 release
+    def test_evalsha_ro(self, unstable_r):
+        unstable_r.set("a", "b")
+        get_sha = unstable_r.script_load("return redis.call('GET', KEYS[1])")
+        del_sha = unstable_r.script_load("return redis.call('DEL', KEYS[1])")
+        assert unstable_r.evalsha_ro(get_sha, 1, "a") == b"b"
+        with pytest.raises(redis.ResponseError):
+            unstable_r.evalsha_ro(del_sha, 1, "a")
+
     def test_evalsha_script_not_loaded(self, r):
         r.set("a", 2)
         sha = r.script_load(multiply_script)