[FIX] core: session logout after 16.0 migration

Create a 15.0 database with website, access the home page via your
browser. Stop the server and migrate the database to 16.0. Restart the
server with a `--dbfilter` that rejects the database you created and
refresh your browser. 500 Internal server error, attribute error:
the `request` object as no `session`.

An error could occurs after a migration to 16.0 due to the presence of
the `geoip` key in the session. `request.session.geoip` has been made a
deprecated alias to `request.geoip` between 15.0 and 16.0, see 04e9726.

Because the session was created before 16.0, the session dict does
contain a `geoip` key. Upon logging the session out, the session dict
is cleared. The default implementation of `clear()`[^1] inside of
`collections.abc.MutableMapping` can be summarized for our usecase to:

    for key in self:
        value = self[key]
        del self[key]

There is an extra `__getitem__` call due to `value = self[key]`, in the
case of the `geoip` key, it would access the alias. It is not possible
to accessing that alias inside of the `_get_dbname_and_session` method
of request as the session has not been set on `self` (the request) yet.

Yet inside of that method, we do `session.logout()` which `clear()` the
session which (wrongly) access the alias because `geoip` exists in the
internal dict (`'geoip' in self.keys()  # True`).

The solution has been to implement the `clear()` function ourself
instead of using the mixin of `MutableMapping`.

[^1]: https://github.com/python/cpython/blob/b43496c01a554cf41ae654a0379efae18609ad39/Lib/_collections_abc.py#L925-L931

closes odoo/odoo#105763

X-original-commit: b66e1ffa8e348eedf2de735babbc398290a8bffb
Signed-off-by: Julien Castiaux <juc@odoo.com>

odoo/addons/test_http/tests/test_session.py

@@ -1,5 +1,6 @@
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
+from urllib.parse import urlparse
 from unittest.mock import patch
 
 import odoo
@@ -74,3 +75,19 @@ class TestHttpSession(TestHttpBase):
             res.raise_for_status()
             self.assertEqual(res.text, str(GEOIP_ODOO_FARM_2))
             mock_resolve.assert_called_once()
+
+    def test_session3_logout_15_0_geoip(self):
+        session = self.authenticate(None, None)
+        session['db'] = 'idontexist'
+        session['geoip'] = {}  # Until saas-15.2 geoip was directly stored in the session
+        odoo.http.root.session_store.save(session)
+
+        with self.assertLogs('odoo.http', level='WARNING') as (_, warnings):
+            res = self.multidb_url_open('/test_http/ensure_db', dblist=['db1', 'db2'])
+
+        self.assertEqual(warnings, [
+            "WARNING:odoo.http:Logged into database 'idontexist', but dbfilter rejects it; logging session out.",
+        ])
+        self.assertFalse(session['db'])
+        self.assertEqual(res.status_code, 303)
+        self.assertEqual(urlparse(res.headers['Location']).path, '/web/database/selector')

odoo/http.py

@@ -915,6 +915,10 @@ class Session(collections.abc.MutableMapping):
         else:
             self[key] = val
 
+    def clear(self):
+        self.data.clear()
+        self.is_dirty = True
+
     #
     # Session methods
     #