From e4d65e3aab980cd8c2347d71bc6e26c19227953b Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 28 Dec 2015 23:58:07 +0200
Subject: [PATCH] Issue #25447: Copying the lru_cache() wrapper object now
 always works, independedly from the type of the wrapped object (by returning
 the original object unchanged).

---
 Lib/test/test_functools.py | 14 ++++++++++++--
 Misc/NEWS                  |  4 ++++
 Modules/_functoolsmodule.c | 16 ++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/Lib/test/test_functools.py b/Lib/test/test_functools.py
index d822b2de457..cf0b95d73c7 100644
--- a/Lib/test/test_functools.py
+++ b/Lib/test/test_functools.py
@@ -1262,14 +1262,24 @@ class TestLRU:
 
     def test_copy(self):
         cls = self.__class__
-        for f in cls.cached_func[0], cls.cached_meth, cls.cached_staticmeth:
+        def orig(x, y):
+            return 3 * x + y
+        part = self.module.partial(orig, 2)
+        funcs = (cls.cached_func[0], cls.cached_meth, cls.cached_staticmeth,
+                 self.module.lru_cache(2)(part))
+        for f in funcs:
             with self.subTest(func=f):
                 f_copy = copy.copy(f)
                 self.assertIs(f_copy, f)
 
     def test_deepcopy(self):
         cls = self.__class__
-        for f in cls.cached_func[0], cls.cached_meth, cls.cached_staticmeth:
+        def orig(x, y):
+            return 3 * x + y
+        part = self.module.partial(orig, 2)
+        funcs = (cls.cached_func[0], cls.cached_meth, cls.cached_staticmeth,
+                 self.module.lru_cache(2)(part))
+        for f in funcs:
             with self.subTest(func=f):
                 f_copy = copy.deepcopy(f)
                 self.assertIs(f_copy, f)
diff --git a/Misc/NEWS b/Misc/NEWS
index 7a0bcef0095..bb0e0568f5d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -36,6 +36,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #25447: Copying the lru_cache() wrapper object now always works,
+  independedly from the type of the wrapped object (by returning the original
+  object unchanged).
+
 - Issue #24103: Fixed possible use after free in ElementTree.XMLPullParser.
 
 - Issue #25860: os.fwalk() no longer skips remaining directories when error
diff --git a/Modules/_functoolsmodule.c b/Modules/_functoolsmodule.c
index fadc0a9c205..035d3d9c591 100644
--- a/Modules/_functoolsmodule.c
+++ b/Modules/_functoolsmodule.c
@@ -1053,6 +1053,20 @@ lru_cache_reduce(PyObject *self, PyObject *unused)
     return PyObject_GetAttrString(self, "__qualname__");
 }
 
+static PyObject *
+lru_cache_copy(PyObject *self, PyObject *unused)
+{
+    Py_INCREF(self);
+    return self;
+}
+
+static PyObject *
+lru_cache_deepcopy(PyObject *self, PyObject *unused)
+{
+    Py_INCREF(self);
+    return self;
+}
+
 static int
 lru_cache_tp_traverse(lru_cache_object *self, visitproc visit, void *arg)
 {
@@ -1104,6 +1118,8 @@ static PyMethodDef lru_cache_methods[] = {
     {"cache_info", (PyCFunction)lru_cache_cache_info, METH_NOARGS},
     {"cache_clear", (PyCFunction)lru_cache_cache_clear, METH_NOARGS},
     {"__reduce__", (PyCFunction)lru_cache_reduce, METH_NOARGS},
+    {"__copy__", (PyCFunction)lru_cache_copy, METH_VARARGS},
+    {"__deepcopy__", (PyCFunction)lru_cache_deepcopy, METH_VARARGS},
     {NULL}
 };