From 854e9b066850b9b4eb1171966e996322b2c16d27 Mon Sep 17 00:00:00 2001
From: Keryn Knight <keryn@kerynknight.com>
Date: Mon, 7 Jun 2021 12:56:50 +0100
Subject: [PATCH] Fixed #32824 -- Improved performance of NodeList.render().

This avoids the following:
 - checking that each item in the nodelist is a subclass of Node,
 - calling str() on the render_annotated() output, because it's
   documented that Node.render() must return a string,
 - calling mark_safe() on the output, when the value to be wrapped is
   definitively known to be a string because the result of ''.join()
   is always of that type,
 - using an intermediate list to store each individual string.
---
 django/template/base.py                     | 13 ++++---------
 docs/releases/4.0.txt                       |  4 ++++
 tests/template_tests/templatetags/custom.py |  2 +-
 3 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/django/template/base.py b/django/template/base.py
index 1446cc865e..4972bd7c58 100644
--- a/django/template/base.py
+++ b/django/template/base.py
@@ -59,7 +59,7 @@ from django.template.context import BaseContext
 from django.utils.formats import localize
 from django.utils.html import conditional_escape, escape
 from django.utils.regex_helper import _lazy_re_compile
-from django.utils.safestring import SafeData, mark_safe
+from django.utils.safestring import SafeData, SafeString, mark_safe
 from django.utils.text import (
     get_text_list, smart_split, unescape_string_literal,
 )
@@ -954,14 +954,9 @@ class NodeList(list):
     contains_nontext = False
 
     def render(self, context):
-        bits = []
-        for node in self:
-            if isinstance(node, Node):
-                bit = node.render_annotated(context)
-            else:
-                bit = node
-            bits.append(str(bit))
-        return mark_safe(''.join(bits))
+        return SafeString(''.join([
+            node.render_annotated(context) for node in self
+        ]))
 
     def get_nodes_by_type(self, nodetype):
         "Return a list of all nodes of the given type"
diff --git a/docs/releases/4.0.txt b/docs/releases/4.0.txt
index 2bdb76ef3d..a9e660f0f1 100644
--- a/docs/releases/4.0.txt
+++ b/docs/releases/4.0.txt
@@ -463,6 +463,10 @@ Miscellaneous
   :class:`~django.utils.feedgenerator.Atom1Feed`, and their subclasses now
   emit elements with no content as self-closing tags.
 
+* ``NodeList.render()`` no longer casts the output of ``render()`` method for
+  individual nodes to a string. ``Node.render()`` should always return a string
+  as documented.
+
 .. _deprecated-features-4.0:
 
 Features deprecated in 4.0
diff --git a/tests/template_tests/templatetags/custom.py b/tests/template_tests/templatetags/custom.py
index da7dd0a878..8efd70147a 100644
--- a/tests/template_tests/templatetags/custom.py
+++ b/tests/template_tests/templatetags/custom.py
@@ -198,4 +198,4 @@ class CounterNode(template.Node):
     def render(self, context):
         count = self.count
         self.count = count + 1
-        return count
+        return str(count)