Remove the 'no cover' pragma and fix a real bug

spark/spark_mails/api.py

@@ -14,8 +14,8 @@ def process_mail_events(iterable, *, defaults=None, fail_silently=False):
         if e["group"] in mails:
             # TODO What about invalid templates? (They should not be saveable, but...)
             subject, body = mails[e["group"]].render(e["context"])
-            if subject:  # pragma: no cover (unlikely)
+            if subject:
                 kwargs["subject"] = subject
-            if body:  # pragma: no cover (unlikely)
+            if body:
                 kwargs["body"] = body
         EmailMessage(**kwargs).send(fail_silently=fail_silently)

spark/spark_mails/models.py

@@ -39,9 +39,12 @@ def render(self, context):
             for line in self.template.render(Context(context)).splitlines()
         )
         subject = ""
-        while True:
-            line = next(lines)
-            if line:
-                subject = line
-                break
+        try:
+            while True:
+                line = next(lines)
+                if line:
+                    subject = line
+                    break
+        except StopIteration:  # if lines is empty
+            pass
         return subject, "\n".join(lines).strip("\n")

tests/testapp/test_mails.py

@@ -57,6 +57,7 @@ def test_mails(self):
         self.assertEqual(len(mail.outbox), 1)
         sent = mail.outbox[0]
         self.assertEqual(sent.to, [user.email])
+        self.assertEqual(sent.subject, "Dear test")
 
     def test_invalid_mail(self):
         m = Mail(event_group="test", template_source="""{{ Bla.21342._"*32424 }}""")
@@ -108,3 +109,31 @@ def test_admin(self):
         m = Mail.objects.create(event_group="stuff_mail", template_source=MAIL)
         response = client.get("/admin/spark_mails/mail/{}/change/".format(m.pk))
         self.assertContains(response, "Best regards</code></div>")
+
+    def test_empty_template(self):
+        Mail.objects.create(event_group="stuff_mail", template_source="")
+        user = User.objects.create(username="test", email="test@example.com")
+        stuff = Stuff.objects.create(key="asdf")
+        events = [
+            {
+                "group": "stuff_mail",
+                "key": "stuff_mail_2",
+                "context": {
+                    "key": stuff.key,
+                    "key_length": len(stuff.key),
+                    "user": user,
+                    "spark_mail": {
+                        "to": [user.email],
+                        "subject": "Would be overridden if template had content",
+                    },
+                },
+            },
+            {"group": "stuff_stuff", "key": "stuff_stuff_1", "context": {}},
+        ]
+        api.process_mail_events(only_new_events(events))
+        api.process_mail_events(only_new_events(events))  # Twice.
+
+        self.assertEqual(len(mail.outbox), 1)
+        sent = mail.outbox[0]
+        self.assertEqual(sent.to, [user.email])
+        self.assertEqual(sent.subject, "Would be overridden if template had content")