Disable querystrings if a storage backend with hashed filenames is active

wagtail/admin/staticfiles.py

@@ -1,12 +1,34 @@
 import hashlib
 
 from django.conf import settings
+from django.contrib.staticfiles.storage import HashedFilesMixin
+from django.core.files.storage import get_storage_class
 from django.templatetags.static import static
 
 from wagtail import __version__
 
 
-if getattr(settings, 'WAGTAILADMIN_STATIC_FILE_VERSION_STRINGS', True):
+# Check whether we should add cache-busting '?v=...' parameters to static file URLs
+try:
+    # If a preference has been explicitly stated in the WAGTAILADMIN_STATIC_FILE_VERSION_STRINGS
+    # setting, use that
+    use_version_strings = settings.WAGTAILADMIN_STATIC_FILE_VERSION_STRINGS
+except AttributeError:
+    # If WAGTAILADMIN_STATIC_FILE_VERSION_STRINGS not specified, default to version strings
+    # enabled, UNLESS we're using a storage backend with hashed filenames; in this case having
+    # a query parameter is redundant, and in some configurations (e.g. Cloudflare with the
+    # "No Query String" setting) it could break a previously-working cache setup
+
+    if settings.DEBUG:
+        # Hashed filenames are disabled in debug mode, so keep the querystring
+        use_version_strings = True
+    else:
+        # see if we're using a storage backend using hashed filenames
+        storage = get_storage_class(settings.STATICFILES_STORAGE)
+        use_version_strings = not issubclass(storage, HashedFilesMixin)
+
+
+if use_version_strings:
     VERSION_HASH = hashlib.sha1(
         (__version__ + settings.SECRET_KEY).encode('utf-8')
     ).hexdigest()[:8]