From 562898034f65e17bcdd2d951ac5236a1ec8ea690 Mon Sep 17 00:00:00 2001
From: Adam Johnson <me@adamj.eu>
Date: Fri, 19 Mar 2021 11:23:28 +0000
Subject: [PATCH] Refs #31732 -- Fixed django.utils.inspect caching for bound
 methods.

Thanks Alexandr Artemyev for the report, and Simon Charette for the
original patch.
---
 django/utils/inspect.py           | 33 ++++++++++++++++++++-----------
 tests/utils_tests/test_inspect.py | 10 ++++++++++
 2 files changed, 31 insertions(+), 12 deletions(-)

diff --git a/django/utils/inspect.py b/django/utils/inspect.py
index 567efcbc17..7e062244e5 100644
--- a/django/utils/inspect.py
+++ b/django/utils/inspect.py
@@ -3,14 +3,23 @@ import inspect
 
 
 @functools.lru_cache(maxsize=512)
-def _get_signature(func):
-    return inspect.signature(func)
+def _get_func_parameters(func, remove_first):
+    parameters = tuple(inspect.signature(func).parameters.values())
+    if remove_first:
+        parameters = parameters[1:]
+    return parameters
+
+
+def _get_callable_parameters(meth_or_func):
+    is_method = inspect.ismethod(meth_or_func)
+    func = meth_or_func.__func__ if is_method else meth_or_func
+    return _get_func_parameters(func, remove_first=is_method)
 
 
 def get_func_args(func):
-    sig = _get_signature(func)
+    params = _get_callable_parameters(func)
     return [
-        arg_name for arg_name, param in sig.parameters.items()
+        param.name for param in params
         if param.kind == inspect.Parameter.POSITIONAL_OR_KEYWORD
     ]
 
@@ -21,10 +30,10 @@ def get_func_full_args(func):
     does not have a default value, omit it in the tuple. Arguments such as
     *args and **kwargs are also included.
     """
-    sig = _get_signature(func)
+    params = _get_callable_parameters(func)
     args = []
-    for arg_name, param in sig.parameters.items():
-        name = arg_name
+    for param in params:
+        name = param.name
         # Ignore 'self'
         if name == 'self':
             continue
@@ -42,7 +51,7 @@ def get_func_full_args(func):
 def func_accepts_kwargs(func):
     """Return True if function 'func' accepts keyword arguments **kwargs."""
     return any(
-        p for p in _get_signature(func).parameters.values()
+        p for p in _get_callable_parameters(func)
         if p.kind == p.VAR_KEYWORD
     )
 
@@ -52,7 +61,7 @@ def func_accepts_var_args(func):
     Return True if function 'func' accepts positional arguments *args.
     """
     return any(
-        p for p in _get_signature(func).parameters.values()
+        p for p in _get_callable_parameters(func)
         if p.kind == p.VAR_POSITIONAL
     )
 
@@ -60,11 +69,11 @@ def func_accepts_var_args(func):
 def method_has_no_args(meth):
     """Return True if a method only accepts 'self'."""
     count = len([
-        p for p in _get_signature(meth).parameters.values()
+        p for p in _get_callable_parameters(meth)
         if p.kind == p.POSITIONAL_OR_KEYWORD
     ])
     return count == 0 if inspect.ismethod(meth) else count == 1
 
 
-def func_supports_parameter(func, parameter):
-    return parameter in _get_signature(func).parameters
+def func_supports_parameter(func, name):
+    return any(param.name == name for param in _get_callable_parameters(func))
diff --git a/tests/utils_tests/test_inspect.py b/tests/utils_tests/test_inspect.py
index 9ea8ae84a4..ae83d675fe 100644
--- a/tests/utils_tests/test_inspect.py
+++ b/tests/utils_tests/test_inspect.py
@@ -22,6 +22,16 @@ class Person:
 
 
 class TestInspectMethods(unittest.TestCase):
+    def test_get_callable_parameters(self):
+        self.assertIs(
+            inspect._get_callable_parameters(Person.no_arguments),
+            inspect._get_callable_parameters(Person.no_arguments),
+        )
+        self.assertIs(
+            inspect._get_callable_parameters(Person().no_arguments),
+            inspect._get_callable_parameters(Person().no_arguments),
+        )
+
     def test_get_func_full_args_no_arguments(self):
         self.assertEqual(inspect.get_func_full_args(Person.no_arguments), [])
         self.assertEqual(inspect.get_func_full_args(Person().no_arguments), [])