parser: prevent IntegrityErrors

Currently, the parser relies on causing (and catching) IntegrityErrors
on patch insert to catch duplicate (msgid,project) mails.

This change performs an atomic select -> insert instead.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Stephen Finucane <stephen@that.guru>
[stephenfin: Remove 'expectedFailure' marker again]

Author: jk-ozlabs

patchwork/parser.py

@@ -1069,7 +1069,10 @@ def parse_mail(mail, list_id=None):
             filenames = find_filenames(diff)
             delegate = find_delegate_by_filename(project, filenames)
 
-        try:
+        with transaction.atomic():
+            if Patch.objects.filter(project=project, msgid=msgid):
+                raise DuplicateMailError(msgid=msgid)
+
             patch = Patch.objects.create(
                 msgid=msgid,
                 project=project,
@@ -1084,8 +1087,6 @@ def parse_mail(mail, list_id=None):
                 delegate=delegate,
                 state=find_state(mail))
             logger.debug('Patch saved')
-        except IntegrityError:
-            raise DuplicateMailError(msgid=msgid)
 
         for attempt in range(1, 11):  # arbitrary retry count
             try:

patchwork/tests/test_parser.py

@@ -1138,7 +1138,6 @@ def log_query_errors(execute, sql, params, many, context):
 
         self.assertEqual(errors, [])
 
-    @unittest.expectedFailure
     def test_duplicate_patch(self):
         diff = read_patch('0001-add-line.patch')
         m = create_email(diff, listid=self.listid, msgid='1@example.com')