Fixed #23755 -- Added support for multiple field names in the no-cache Cache-Control directive to patch_cache_control().

https://tools.ietf.org/html/rfc7234#section-5.2.2.2

1 files changed, 27 insertions, 7 deletions

diff --git a/django/utils/cache.py b/django/utils/cache.py
index 3ee01a1e94..14e8256b94 100644
--- a/django/utils/cache.py
+++ b/django/utils/cache.py
@@ -19,6 +19,7 @@ An example: i18n middleware would need to distinguish caches by the
 import hashlib
 import re
 import time
+from collections import defaultdict
 
 from django.conf import settings
 from django.core.cache import caches
@@ -53,17 +54,21 @@ def patch_cache_control(response, **kwargs):
         else:
             return (t[0].lower(), True)
 
-    def dictvalue(t):
+    def dictvalue(*t):
         if t[1] is True:
             return t[0]
         else:
             return '%s=%s' % (t[0], t[1])
 
+    cc = defaultdict(set)
     if response.get('Cache-Control'):
-        cc = cc_delim_re.split(response['Cache-Control'])
-        cc = dict(dictitem(el) for el in cc)
-    else:
-        cc = {}
+        for field in cc_delim_re.split(response['Cache-Control']):
+            directive, value = dictitem(field)
+            if directive == 'no-cache':
+                # no-cache supports multiple field names.
+                cc[directive].add(value)
+            else:
+                cc[directive] = value
 
     # If there's already a max-age header but we're being asked to set a new
     # max-age, use the minimum of the two ages. In practice this happens when
@@ -78,8 +83,23 @@ def patch_cache_control(response, **kwargs):
         del cc['public']
 
     for (k, v) in kwargs.items():
-        cc[k.replace('_', '-')] = v
-    cc = ', '.join(dictvalue(el) for el in cc.items())
+        directive = k.replace('_', '-')
+        if directive == 'no-cache':
+            # no-cache supports multiple field names.
+            cc[directive].add(v)
+        else:
+            cc[directive] = v
+
+    directives = []
+    for directive, values in cc.items():
+        if isinstance(values, set):
+            if True in values:
+                # True takes precedence.
+                values = {True}
+            directives.extend([dictvalue(directive, value) for value in values])
+        else:
+            directives.append(dictvalue(directive, values))
+    cc = ', '.join(directives)
     response['Cache-Control'] = cc