Fix append in BodyMailsParts when follow is true and list is empty + tests

tracim/tracim/lib/email_processing/models.py

         BodyMailParts._check_value(value)
         self._append(value)
 
-    def _append(self, value) -> None:
-        same_type_as_last = len(self._list) > 0 and \
-                            self._list[-1].part_type == value.part_type
-        if same_type_as_last or self.follow:
-            self._list[-1].text += value.text
-        else:
+    def _append(self, value, follow=None) -> None:
+        if follow is None:
+            follow = self.follow
+
+        if len(self._list) < 1:
             self._list.append(value)
+        else:
+            if self._list[-1].part_type == value.part_type or follow:
+                self._list[-1].text += value.text
+            else:
+                self._list.append(value)
 
     @classmethod
     def _check_value(cls, value) -> None:
         """
         new_list = [x for x in self._list if x.part_type != part_type]
         self._list = []
+
         # INFO - G.M - 2017-11-27 - use append() to have a consistent list
         for elem in new_list:
-            self.append(elem)
+            self._append(elem, follow=False)
 
     def get_nb_part_type(self, part_type: str) -> int:
         """

tracim/tracim/tests/library/test_email_body_parser.py

         assert mail_parts[0] == a
         assert mail_parts[1] == b
 
+    def test_unit__append_follow(self):
+        mail_parts = BodyMailParts()
+        mail_parts.follow = True
+        a = BodyMailPart('a', BodyMailPartType.Main)
+        mail_parts._append(a)
+        b = BodyMailPart('b', BodyMailPartType.Quote)
+        mail_parts._append(b)
+        assert len(mail_parts) == 1
+        assert mail_parts[0].part_type == BodyMailPartType.Main
+        assert mail_parts[0].text == 'ab'
+
+    def test_unit__append_dont_follow_when_first(self):
+        mail_parts = BodyMailParts()
+        a = BodyMailPart('a', BodyMailPartType.Main)
+        mail_parts._append(a,follow=True)
+        assert len(mail_parts) == 1
+        assert mail_parts[0].part_type == BodyMailPartType.Main
+        assert mail_parts[0].text == 'a'
+
     @raises(TypeError)
     def test_unit__check_value__type_error(self):
         mail_parts = BodyMailParts()
         assert mail_parts[1].text == 'c'
         assert mail_parts[1].part_type == BodyMailPartType.Signature
 
+    def test_unit__drop_part_type_verify_no_follow_incidence(self):
+        mail_parts = BodyMailParts()
+        a = BodyMailPart('a', BodyMailPartType.Main)
+        mail_parts._list.append(a)
+        b = BodyMailPart('b', BodyMailPartType.Quote)
+        mail_parts._list.append(b)
+        c = BodyMailPart('c', BodyMailPartType.Signature)
+        mail_parts._list.append(c)
+        mail_parts.follow = True
+        mail_parts.drop_part_type(BodyMailPartType.Quote)
+        assert len(mail_parts) == 2
+        assert mail_parts[0].text == 'a'
+        assert mail_parts[0].part_type == BodyMailPartType.Main
+        assert len(mail_parts) == 2
+        assert mail_parts[1].text == 'c'
+        assert mail_parts[1].part_type == BodyMailPartType.Signature
+
     def test_unit__drop_part_type_consistence(self):
         mail_parts = BodyMailParts()
         a = BodyMailPart('a', BodyMailPartType.Main)
         assert mail_parts[0].text == 'ac'
         assert mail_parts[0].part_type == BodyMailPartType.Main
 
+
     def test_unit__get_nb_part_type(self):
         mail_parts = BodyMailParts()
         assert mail_parts.get_nb_part_type(BodyMailPartType.Main) == 0