Fix accept header scenario, add tests

Author: allcaps

apps/core/middleware.py

@@ -1,4 +1,4 @@
-from django.http import Http404
+from django.conf import settings
 from django.urls import LocalePrefixPattern
 from django.utils.translation import activate, get_language
 
@@ -12,16 +12,18 @@ def __init__(self, get_response):
         self.get_response = get_response
 
     def __call__(self, request):
-        response = self.get_response(request)
-        if request.resolver_match:
-            # Check if the path is in the i18n_patterns
-            if pattern.match(request.resolver_match.route):
-                try:
-                    HomePage.objects.get(
-                        locale__language_code=get_language(), live=True
-                    )
-                except HomePage.DoesNotExist:
-                    # Activate English so that we have a site menu
-                    activate("en-latest")
-                    raise Http404()
+        if (
+            request.path == "/"
+            or request.resolver_match
+            and pattern.match(request.resolver_match.route)
+        ):
+            try:
+                HomePage.objects.get(locale__language_code=get_language(), live=True)
+                response = self.get_response(request)
+            except HomePage.DoesNotExist:
+                # The requested language is not available, use the default
+                activate(settings.LANGUAGE_CODE)
+                response = self.get_response(request)
+        else:
+            response = self.get_response(request)
         return response

apps/core/tests/test_middleware.py

@@ -0,0 +1,120 @@
+from http import HTTPStatus
+
+from django.conf import settings
+from django.test import TestCase
+from django.urls import reverse
+from wagtail.snippets.models import register_snippet
+
+from apps.core.factories import HomePageFactory, LocaleFactory
+
+
+class TestValidateLocaleMiddleware(TestCase):
+    """
+    LocaleMiddleware tries to determine the user’s language preference by following
+    this algorithm:
+
+    1. First, it looks for the language prefix in the requested URL.
+    2. Failing that, it looks for a cookie, named `django_language`.
+    3. Failing that, it looks at the Accept-Language HTTP header. This header is sent by
+       your browser and tells the server which language(s) you prefer, in order by
+       priority. Django tries each language in the header until it finds one with
+       available translations.
+    4. Failing that, it uses the global LANGUAGE_CODE setting.
+
+    Wagtail Guide has all languages in LANGUAGES setting, therefore LocaleMiddleware
+    will redirect to any language prefix URL. Unfortunately, Wagtail might not have
+    the corresponding homepage for that language published. If Wagtail has no
+    homepage available for the requested language, it raises a 404.
+
+    This behaviour is undesirable. As step 3 of the algoritm will end up in a 404.
+    To resolve this issue, we introduce our ValidateLocaleMiddleware.
+
+    ValidateLocaleMiddleware checks for a published homepage for the requested language.
+    If it does not exist, it falls back to English. The default, and always published
+    language/homepage.
+
+    The ValidateLocaleMiddleware kicks in on `/` and any i18n pattern.
+    Other URLs are ignored, and have the default LocaleMiddleware behaviour.
+    """
+
+    def setUp(self):
+        self.en = LocaleFactory(language_code="en-latest")
+        self.home_en = HomePageFactory(locale=self.en)
+
+    def test_middleware_settings(self):
+        self.assertIn("django.middleware.locale.LocaleMiddleware", settings.MIDDLEWARE)
+        self.assertIn(
+            "apps.core.middleware.ValidateLocaleMiddleware", settings.MIDDLEWARE
+        )
+        self.assertGreater(
+            settings.MIDDLEWARE.index("apps.core.middleware.ValidateLocaleMiddleware"),
+            settings.MIDDLEWARE.index("django.middleware.locale.LocaleMiddleware"),
+        )
+
+    def test_request_root_redirects_to_language_code(self):
+        self.assertEqual(settings.LANGUAGE_CODE, "en-latest")
+        response = self.client.get("/")
+        self.assertEqual(response.status_code, HTTPStatus.FOUND)
+        self.assertEqual(response.url, "/en-latest/")
+        self.assertEqual(self.client.get("/en-latest/").status_code, HTTPStatus.OK)
+
+    def test_request_root_with_accept_language_header(self):
+        # To English, if German doesn't exist
+        response = self.client.get("/", HTTP_ACCEPT_LANGUAGE="de")
+        self.assertEqual(response.status_code, HTTPStatus.FOUND)
+        self.assertEqual(response.url, "/en-latest/")
+        self.assertEqual(self.client.get("/en-latest/").status_code, HTTPStatus.OK)
+        # To German, if German exists
+        de = LocaleFactory(language_code="de-latest")
+        self.home_de = self.home_en.copy_for_translation(locale=de)
+        self.home_de.save_revision().publish()
+        response = self.client.get("/", HTTP_ACCEPT_LANGUAGE="de")
+        self.assertEqual(response.status_code, HTTPStatus.FOUND)
+        self.assertEqual(response.url, "/de-latest/")
+        self.assertEqual(self.client.get("/de-latest/").status_code, HTTPStatus.OK)
+
+    def test_request_root_with_cookie(self):
+        self.assertEqual(settings.LANGUAGE_COOKIE_NAME, "django_language")
+        de = LocaleFactory(language_code="de-latest")
+        self.home_de = self.home_en.copy_for_translation(locale=de)
+        self.home_de.save_revision().publish()
+        # The HTTP_ACCEPT_LANGUAGE is ignored, the cookie takes precedence
+        self.client.cookies["django_language"] = "en-latest"
+        response = self.client.get("/", HTTP_ACCEPT_LANGUAGE="de")
+        self.assertEqual(response.status_code, HTTPStatus.FOUND)
+        self.assertEqual(response.url, "/en-latest/")
+        self.assertEqual(self.client.get("/en-latest/").status_code, HTTPStatus.OK)
+
+    def test_request_specific_url(self):
+        de = LocaleFactory(language_code="de-latest")
+        self.home_de = self.home_en.copy_for_translation(locale=de)
+        self.home_de.save_revision().publish()
+        # The HTTP_ACCEPT_LANGUAGE is ignored
+        self.client.cookies["django_language"] = "de"
+        # The HTTP_ACCEPT_LANGUAGE is ignored
+        response = self.client.get("/en-latest/", HTTP_ACCEPT_LANGUAGE="de")
+        self.assertEqual(response.status_code, HTTPStatus.OK)
+
+    def test_wagtail_admin_respects_accept_language(self):
+        # Non i18n_patterns respect HTTP_ACCEPT_LANGUAGE
+        url = reverse("wagtailadmin_login")
+        response = self.client.get(url, HTTP_ACCEPT_LANGUAGE="nl")
+        expected = "<h1>Inloggen in Wagtail</h1>"
+        self.assertInHTML(expected, str(response.content))
+
+    def test_django_admin_respects_accept_language(self):
+        # Non i18n_patterns respect HTTP_ACCEPT_LANGUAGE
+        url = reverse("admin:login")
+        response = self.client.get(url, HTTP_ACCEPT_LANGUAGE="nl")
+        expected = '<h1 id="site-name"><a href="/django-admin/">Django-beheer</a></h1>'
+        self.assertInHTML(expected, str(response.content))
+
+    def test_sitemap_xml(self):
+        # Non i18n_patterns respect HTTP_ACCEPT_LANGUAGE
+        url = "/sitemap.xml"
+        response = self.client.get(url, HTTP_ACCEPT_LANGUAGE="nl")
+        expected = (
+            b'<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" '
+            b'xmlns:xhtml="http://www.w3.org/1999/xhtml">'
+        )
+        self.assertIn(expected, response.content)