From 0f5183eb467bb8e406c9a42ddd80473b1477aa54 Mon Sep 17 00:00:00 2001
From: Stijn de Gooijer <stijndegooijer@gmail.com>
Date: Fri, 15 Mar 2024 15:47:25 +0100
Subject: [PATCH] Re-add deprecation warning

---
 py-polars/polars/expr/expr.py  |  3 +++
 py-polars/polars/utils/udfs.py | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/py-polars/polars/expr/expr.py b/py-polars/polars/expr/expr.py
index 14a00f81eafa..53f202b52572 100644
--- a/py-polars/polars/expr/expr.py
+++ b/py-polars/polars/expr/expr.py
@@ -9622,6 +9622,9 @@ def shift_and_fill(
         """
         return self.shift(n, fill_value=fill_value)
 
+    @deprecate_function(
+        "Use `polars.plugins.register_plugin_function` instead.", version="0.20.16"
+    )
     def register_plugin(
         self,
         *,
diff --git a/py-polars/polars/utils/udfs.py b/py-polars/polars/utils/udfs.py
index bc4db0efe087..f7ee74e0eece 100644
--- a/py-polars/polars/utils/udfs.py
+++ b/py-polars/polars/utils/udfs.py
@@ -3,9 +3,19 @@
 import os
 from typing import Any
 
+from polars._utils.deprecation import deprecate_function
+
 __all__ = ["_get_shared_lib_location"]
 
 
+@deprecate_function(
+    "It will be removed in the next breaking release."
+    " The new `register_plugin_function` function has this functionality built in."
+    " Use `from polars.plugins import register_plugin_function` to import that function."
+    " Check the user guide for the currently-recommended way to register a plugin:"
+    " https://docs.pola.rs/user-guide/expressions/plugins",
+    version="0.20.16",
+)
 def _get_shared_lib_location(main_file: Any) -> str:
     """
     Get the location of the dynamic library file.