[IMP] mail: make res_model of followers model a related on m2o towards ir.model

When uninstalling a module followers stay in the database because there is no
real link between ir.model and followers. Adding a m2o ensure followers are
correctly removed when uninstalling a module.

res_model fields is kept as a stored related field. This allows to keep
compatibility with almost all code using / searching on followers. Only
followers creation is changed a bit. As follower creation is done mainly
through a dedicated method few changes are required. Yey. Mat should be
happier now.

fix test

3 files changed, 20 insertions, 13 deletions

diff --git a/addons/mail/models/mail_followers.py b/addons/mail/models/mail_followers.py
index 9377d12832b..304003fa4fc 100644
--- a/addons/mail/models/mail_followers.py
+++ b/addons/mail/models/mail_followers.py
@@ -18,8 +18,12 @@ class Followers(models.Model):
     _log_access = False
     _description = 'Document Followers'
 
+    res_model_id = fields.Many2one(
+        'ir.model', 'Related Document Model',
+        index=True, ondelete='cascade',
+        help='Model of the followed resource')
     res_model = fields.Char(
-        'Related Document Model', required=True, index=True, help='Model of the followed resource')
+        'Related Document Model Name', index=True, readonly=True, related='res_model_id.model', store=True)
     res_id = fields.Integer(
         'Related Document ID', index=True, help='Id of the followed resource')
     partner_id = fields.Many2one(
@@ -36,6 +40,7 @@ class Followers(models.Model):
         :param force: if True, delete existing followers before creating new one
                       using the subtypes given in the parameters
         """
+        res_model_id = self.env['ir.model'].search([('model', '=', res_model)], limit=1).id
         force_mode = force or (all(data for data in partner_data.values()) and all(data for data in channel_data.values()))
         generic = []
         specific = {}
@@ -74,9 +79,9 @@ class Followers(models.Model):
         gen_new_pids = [pid for pid in partner_data.keys() if pid not in p_exist]
         gen_new_cids = [cid for cid in channel_data.keys() if cid not in c_exist]
         for pid in gen_new_pids:
-            generic.append([0, 0, {'res_model': res_model, 'partner_id': pid, 'subtype_ids': [(6, 0, partner_data.get(pid) or default_subtypes.ids)]}])
+            generic.append([0, 0, {'res_model_id': res_model_id, 'partner_id': pid, 'subtype_ids': [(6, 0, partner_data.get(pid) or default_subtypes.ids)]}])
         for cid in gen_new_cids:
-            generic.append([0, 0, {'res_model': res_model, 'channel_id': cid, 'subtype_ids': [(6, 0, channel_data.get(cid) or default_subtypes.ids)]}])
+            generic.append([0, 0, {'res_model_id': res_model_id, 'channel_id': cid, 'subtype_ids': [(6, 0, channel_data.get(cid) or default_subtypes.ids)]}])
 
         # create new followers, each document at a time because of existing followers to avoid erasing
         if not force_mode:
@@ -90,13 +95,13 @@ class Followers(models.Model):
                 # subscribe new followers
                 for new_pid in new_pids:
                     command.append((0, 0, {
-                        'res_model': res_model,
+                        'res_model_id': res_model_id,
                         'partner_id': new_pid,
                         'subtype_ids': [(6, 0, partner_data.get(new_pid) or default_subtypes.ids)],
                     }))
                 for new_cid in new_cids:
                     command.append((0, 0, {
-                        'res_model': res_model,
+                        'res_model_id': res_model_id,
                         'channel_id': new_cid,
                         'subtype_ids': [(6, 0, channel_data.get(new_cid) or default_subtypes.ids)],
                     }))
diff --git a/addons/mail/tests/test_mail_followers.py b/addons/mail/tests/test_mail_followers.py
index 5ea0667d7eb..db028ef3f65 100644
--- a/addons/mail/tests/test_mail_followers.py
+++ b/addons/mail/tests/test_mail_followers.py
@@ -25,11 +25,12 @@ class TestMailFollowers(TestMail):
             'mail.channel', groups.ids,
             {self.user_employee.partner_id.id: [self.mt_mg_nodef.id]},
             {test_channel.id: [self.mt_al_nodef.id]})
+        mail_channel_model_id = self.env['ir.model'].search([('model', '=', 'mail.channel')], limit=1).id
         self.assertFalse(specific)
         self.assertEqual(len(generic), 2)
 
-        self.assertEqual(set([generic[0][2]['res_model'], generic[1][2]['res_model']]),
-                         set(['mail.channel']))
+        self.assertEqual(set([generic[0][2]['res_model_id'], generic[1][2]['res_model_id']]),
+                         set([mail_channel_model_id]))
         self.assertEqual(set(filter(None, [generic[0][2].get('channel_id'), generic[1][2].get('channel_id')])),
                          set([test_channel.id]))
         self.assertEqual(set(filter(None, [generic[0][2].get('partner_id'), generic[1][2].get('partner_id')])),
@@ -39,8 +40,9 @@ class TestMailFollowers(TestMail):
 
     def test_m2o_command_update_selective(self):
         test_channel = self.env['mail.channel'].create({'name': 'Test'})
+        mail_channel_model_id = self.env['ir.model'].search([('model', '=', 'mail.channel')], limit=1).id
         groups = self.group_pigs | self.group_public
-        self.env['mail.followers'].create({'partner_id': self.user_employee.partner_id.id, 'res_model': 'mail.channel', 'res_id': self.group_pigs.id})
+        self.env['mail.followers'].create({'partner_id': self.user_employee.partner_id.id, 'res_model_id': mail_channel_model_id, 'res_id': self.group_pigs.id})
         generic, specific = self.env['mail.followers']._add_follower_command(
             'mail.channel', groups.ids,
             {self.user_employee.partner_id.id: [self.mt_mg_nodef.id]},
@@ -49,12 +51,12 @@ class TestMailFollowers(TestMail):
         self.assertEqual(len(generic), 1)
         self.assertEqual(len(specific), 1)
 
-        self.assertEqual(generic[0][2]['res_model'], 'mail.channel')
+        self.assertEqual(generic[0][2]['res_model_id'], mail_channel_model_id)
         self.assertEqual(generic[0][2]['channel_id'], test_channel.id)
         self.assertEqual(set(generic[0][2]['subtype_ids'][0][2]), set(self.default_group_subtypes.ids))
 
         self.assertEqual(specific.keys(), [self.group_public.id])
-        self.assertEqual(specific[self.group_public.id][0][2]['res_model'], 'mail.channel')
+        self.assertEqual(specific[self.group_public.id][0][2]['res_model_id'], mail_channel_model_id)
         self.assertEqual(specific[self.group_public.id][0][2]['partner_id'], self.user_employee.partner_id.id)
         self.assertEqual(set(specific[self.group_public.id][0][2]['subtype_ids'][0][2]), set([self.mt_mg_nodef.id]))
 
@@ -118,7 +120,7 @@ class TestMailFollowers(TestMail):
         })
         with self.assertRaises(IntegrityError):
             self.env['mail.followers'].create({
-                'res_model': 'mail.channel',
+                'res_model_id': self.env['ir.model'].search([('model', '=', 'mail.channel')], limit=1).id,
                 'res_id': test_channel.id,
                 'partner_id': self.user_employee.partner_id.id,
                 'channel_id': self.group_pigs.id,
diff --git a/addons/mail/views/mail_followers_views.xml b/addons/mail/views/mail_followers_views.xml
index fa5cfbf0116..adbea78d7f5 100644
--- a/addons/mail/views/mail_followers_views.xml
+++ b/addons/mail/views/mail_followers_views.xml
@@ -9,7 +9,7 @@
             <field name="priority">10</field>
             <field name="arch" type="xml">
                 <tree string="Followers">
-                    <field name="res_model"/>
+                    <field name="res_model_id"/>
                     <field name="res_id"/>
                     <field name="partner_id"/>
                 </tree>
@@ -24,7 +24,7 @@
                     <sheet>
                         <group>
                             <group>
-                                <field name="res_model"/>
+                                <field name="res_model_id"/>
                                 <field name="partner_id"/>
                             </group>
                             <group>