[FIX] core: add invalidation of Environment's _cache_key.

Changing the environment in method create() to force bin_size=False
looks harmless, but it actually breaks many tests, in particular in
module account.  The reason is that company_dependent fields are read at
the wrong place in the cache.  And this is because `env._cache_key` can
be polluted with old data.

Make sure that `_cache_key` is cleared when resetting all the lazy
properties on the environment.  Only the change in res_user.py makes it
work, but let's not tempt the devil.

Side note: I hate caches.

Part-of: odoo#160708

odoo/addons/base/models/res_users.py

@@ -672,13 +672,15 @@ def write(self, values):
                     user.partner_id.write({'company_id': user.company_id.id})
 
         if 'company_id' in values or 'company_ids' in values:
-            # Reset lazy properties `company` & `companies` on all envs
+            # Reset lazy properties `company` & `companies` on all envs,
+            # and also their _cache_key, which may depend on them.
             # This is unlikely in a business code to change the company of a user and then do business stuff
             # but in case it happens this is handled.
             # e.g. `account_test_savepoint.py` `setup_company_data`, triggered by `test_account_invoice_report.py`
             for env in list(self.env.transaction.envs):
                 if env.user in self:
                     lazy_property.reset_all(env)
+                    env._cache_key.clear()
 
         # clear caches linked to the users
         if self.ids and 'groups_id' in values:

odoo/addons/test_new_api/tests/test_new_fields.py

@@ -2921,6 +2921,27 @@ def test_99_prefetch_group(self):
             records.mapped('harry')  # fetch all fields with prefetch='Harry Potter'
             records.mapped('rare_description')  # fetch that field only
 
+    def test_cache_key_invalidation(self):
+        company0 = self.env.ref('base.main_company')
+        company1 = self.env['res.company'].create({'name': 'A'})
+
+        user0 = self.env['res.users'].create({
+            'name': 'Foo', 'login': 'foo', 'company_id': company0.id,
+            'company_ids': [Command.set([company0.id, company1.id])],
+        })
+
+        # this uses company0
+        record = self.env['test_new_api.company'].with_user(user0).create({
+            'foo': 'main',
+        })
+        self.assertEqual(record.env.company, company0)
+        self.assertEqual(record.foo, 'main')
+
+        # change the user's company, so we implicitly switch to company1
+        user0.company_id = company1
+        self.assertEqual(record.env.company, company1)
+        self.assertEqual(record.foo, False)
+
 
 class TestX2many(common.TransactionCase):
 

odoo/api.py

@@ -697,6 +697,7 @@ def clear(self):
             This may be useful when recovering from a failed ORM operation.
         """
         lazy_property.reset_all(self)
+        self._cache_key.clear()
         self.transaction.clear()
 
     def invalidate_all(self, flush=True):
@@ -873,6 +874,7 @@ def reset(self):
         for env in self.envs:
             env.registry = self.registry
             lazy_property.reset_all(env)
+            env._cache_key.clear()
         self.clear()