Allow i18n of colander error messages

cornice/__init__.py

@@ -2,6 +2,7 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
 # You can obtain one at http://mozilla.org/MPL/2.0/.
 import logging
+from functools import partial
 
 from cornice import util
 from cornice.errors import Errors  # NOQA
@@ -14,7 +15,8 @@
     register_resource_views,
 )
 from cornice.util import ContentTypePredicate
-
+from pyramid.events import BeforeRender, NewRequest
+from pyramid.i18n import get_localizer
 from pyramid.httpexceptions import HTTPNotFound, HTTPForbidden
 from pyramid.security import NO_PERMISSION_REQUIRED
 
@@ -33,11 +35,53 @@ def add_apidoc(config, pattern, func, service, **kwargs):
     info['func'] = func
 
 
+def set_localizer_for_languages(event, available_languages,
+                                default_locale_name):
+    """
+    Sets the current locale based on the incoming Accept-Language header, if
+    present, and sets a localizer attribute on the request object based on
+    the current locale.
+
+    To be used as an event handler, this function needs to be partially applied
+    with the available_languages and default_locale_name arguments. The
+    resulting function will be an event handler which takes an event object as
+    its only argument.
+    """
+    request = event.request
+    if request.accept_language:
+        accepted = request.accept_language
+        locale = accepted.best_match(available_languages, default_locale_name)
+        request._LOCALE_ = locale
+    localizer = get_localizer(request)
+    request.localizer = localizer
+
+
+def setup_localization(config):
+    """
+    Setup localization based on the available_languages and
+    pyramid.default_locale_name settings.
+
+    These settings are named after suggestions from the "Internationalization
+    and Localization" section of the Pyramid documentation.
+    """
+    try:
+        config.add_translation_dirs('colander:locale/')
+        settings = config.get_settings()
+        available_languages = settings['available_languages'].split()
+        default_locale_name = settings.get('pyramid.default_locale_name', 'en')
+        set_localizer = partial(set_localizer_for_languages,
+                                available_languages=available_languages,
+                                default_locale_name=default_locale_name)
+        config.add_subscriber(set_localizer, NewRequest)
+    except ImportError:
+        # add_translation_dirs raises an ImportError if colander is not
+        # installed
+        pass
+
+
 def includeme(config):
     """Include the Cornice definitions
     """
-    from pyramid.events import BeforeRender, NewRequest
-
     # attributes required to maintain services
     config.registry.cornice_services = {}
 
@@ -61,3 +105,6 @@ def includeme(config):
                         permission=NO_PERMISSION_REQUIRED)
         config.add_view(handle_exceptions, context=HTTPForbidden,
                         permission=NO_PERMISSION_REQUIRED)
+
+    if settings.get('available_languages'):
+        setup_localization(config)

cornice/schemas.py

@@ -148,11 +148,13 @@ def _validate_fields(location, data):
                         deserialized = attr.deserialize(serialized)
                 except Invalid as e:
                     # the struct is invalid
+                    translate = request.localizer.translate
+                    error_dict = e.asdict(translate=translate)
                     try:
                         request.errors.add(location, attr.name,
-                                           e.asdict()[attr.name])
+                                           error_dict[attr.name])
                     except KeyError:
-                        for k, v in e.asdict().items():
+                        for k, v in error_dict.items():
                             if k.startswith(attr.name):
                                 request.errors.add(location, k, v)
                 else:

cornice/tests/test_validation.py

@@ -1,3 +1,4 @@
+# -*- encoding: utf-8 -*-
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this file,
 # You can obtain one at http://mozilla.org/MPL/2.0/.
@@ -365,3 +366,55 @@ def low_priority_deserializer(request):
                             "hello,open,yeah",
                             headers={'content-type': 'text/dummy'})
         self.assertEqual(response.json['test'], 'succeeded')
+
+
+class TestErrorMessageTranslation(TestCase):
+
+    def post(self, settings={}, headers={}):
+        app = TestApp(main({}, **settings))
+        return app.post_json('/foobar?yeah=test', {
+            'foo': 'hello',
+            'bar': 'open',
+            'yeah': 'man',
+            'ipsum': 10,
+        }, status=400, headers=headers)
+
+    def assertErrorDescription(self, response, message):
+        error_description = response.json['errors'][0]['description']
+        self.assertEqual(error_description, message)
+
+    def test_accept_language_header(self):
+        response = self.post(
+            settings={'available_languages': 'fr en'},
+            headers={'Accept-Language': 'fr'})
+        self.assertErrorDescription(
+            response,
+            u'10 est plus grand que la valeur maximum autorisée (3)')
+
+    def test_default_language(self):
+        response = self.post(settings={
+            'available_languages': 'fr ja',
+            'pyramid.default_locale_name': 'ja',
+        })
+        self.assertErrorDescription(
+            response,
+            u'10 は最大値 3 を超過しています')
+
+    def test_default_language_fallback(self):
+        """Should fallback to default language if requested language is not
+        available"""
+        response = self.post(
+            settings={
+                'available_languages': 'ja en',
+                'pyramid.default_locale_name': 'ja',
+            },
+            headers={'Accept-Language': 'ru'})
+        self.assertErrorDescription(
+            response,
+            u'10 は最大値 3 を超過しています')
+
+    def test_no_language_settings(self):
+        response = self.post()
+        self.assertErrorDescription(
+            response,
+            u'10 is greater than maximum value 3')

cornice/tests/validationapp.py

@@ -218,6 +218,6 @@ def includeme(config):
 
 
 def main(global_config, **settings):
-    config = Configurator(settings={})
+    config = Configurator(settings=settings)
     config.include(includeme)
     return CatchErrors(config.make_wsgi_app())

docs/source/validation.rst

@@ -201,6 +201,10 @@ before passing the result to Colander.
 View-specific deserializers have priority over global content-type
 deserializers.
 
+To enable localization of Colander error messages, you must set
+`available_languages <http://docs.pylonsproject.org/projects/pyramid/en/1.3-branch/narr/i18n.html#detecting-available-languages>`_ in your settings.
+You may also set `pyramid.default_locale_name <http://docs.pylonsproject.org/projects/pyramid/en/1.3-branch/narr/environment.html#default-locale-name-setting>`_.
+
 
 Using formencode
 ~~~~~~~~~~~~~~~~