[FIX] http_routing: remove trailing /

Currently, the character `/` appears at the end of the url of the
language dropdown on the home page e.g. /en/, /fr/. This will cause one
more redirect when performing the language change.

Indeed, this error is only encountered with path = /
Please try the following `url_lang('/', 'en_US')` => /en/

After this fix, the trailing `/` will be removed when using the func
`url_lang` e.g. `url_lang('', 'en_US')` => /en, this means that the
language switching links on the homepage no longer redirect redundantly
again.

closes odoo/odoo#106109

Signed-off-by: Romain Derie (rde) <rde@odoo.com>

addons/http_routing/models/ir_http.py

@@ -167,6 +167,9 @@ def url_lang(path_or_uri, lang_code=None):
             # Insert the context language or the provided language
             elif lang_url_code != default_lg.url_code or force_lang:
                 ps.insert(1, lang_url_code)
+                # Remove the last empty string to avoid trailing / after joining
+                if ps[-1] == '':
+                    ps.pop(-1)
 
             location = u'/'.join(ps) + sep + qs
     return location

addons/website/tests/test_qweb.py

@@ -77,7 +77,7 @@ class TestQwebProcessAtt(TransactionCase):
 
     def test_process_att_with_request_lang(self):
         with MockRequest(self.env, website=self.website, context={'lang': 'fr_FR'}):
-            self._test_att('/', {'href': '/fr/'})
+            self._test_att('/', {'href': '/fr'})
             self._test_att('/en/', {'href': '/'})
             self._test_att('/fr/', {'href': '/fr/'})
             self._test_att('/fr', {'href': '/fr'})