making flat files delivery more robust

middleware.py

@@ -1,7 +1,6 @@
 from django.conf import settings
 from django import http
-from django.urls import reverse, resolve
-#from django.core.urlresolvers import resolve
+from django.urls import reverse, resolve,Resolver404
 """Non-standard django middleware is loaded from this file.
 """
 
@@ -17,19 +16,31 @@ class SmartAppendSlashMiddleware(object):
     """
 
     def process_request(self, request):
-        """
-        Rewrite the URL based on settings.SMART_APPEND_SLASH
-        """
+        '''Called for every url so return as quickly as possible
+        Append a slash if SMART_APPEND_SLASH is set, the resulting URL resolves and it doesn't without the /
+        '''
+        if not settings.SMART_APPEND_SLASH:
+            return None
+ 
+        if request.path.endswith('/'):
+            return None
+            
+        if request.path.endswith('_edit'):
+            return None
 
-        # Check for a redirect based on settings.SMART_APPEND_SLASH
         host = http.HttpRequest.get_host(request)
         old_url = [host, request.path]
-        new_url = old_url[:]
-        # Append a slash if SMART_APPEND_SLASH is set and the resulting URL
-        # resolves.
-        if settings.SMART_APPEND_SLASH and (not old_url[1].endswith('/')) and not _resolves(old_url[1]) and _resolves(old_url[1] + '/'):
-            new_url[1] = new_url[1] + '/'
+        if _resolves(old_url[1]):
+            return None
+         
+        # So: it does not resolve according to our criteria, i.e. _edit doesn't count
+        new_url = old_url[:]       
+        new_url[1] = new_url[1] + '/'
+        if not _resolves(new_url[1]):
+            return None
+        else:          
             if settings.DEBUG and request.method == 'POST':
+                # replace this exception with a redirect to an error page
                 raise RuntimeError("You called this URL via POST, but the URL doesn't end in a slash and you have SMART_APPEND_SLASH set. Django can't redirect to the slash URL while maintaining POST data. Change your form to point to %s%s (note the trailing slash), or set SMART_APPEND_SLASH=False in your Django settings." % (new_url[0], new_url[1]))
         if new_url != old_url:
             # Redirect
@@ -45,9 +56,12 @@ class SmartAppendSlashMiddleware(object):
 
 def _resolves(url):
     try:
-        resolve(url)
+        # If the URL does not resolve, the function raises a Resolver404 exception (a subclass of Http404) 
+        match = resolve(url)
+        # this will ALWAYS be resolved by expopages because it will produce pagenotfound if not the thing asked for
+        # so handle this in expopages, not in middleware 
         return True
-    except http.Http404:
+    except Resolver404:
         return False
     except:
         print(url)