Implement `locale` filter in API

wagtail/api/v2/filters.py

@@ -1,9 +1,10 @@
 from django.conf import settings
 from django.db import models
+from django.shortcuts import get_object_or_404
 from rest_framework.filters import BaseFilterBackend
 from taggit.managers import TaggableManager
 
-from wagtail.core.models import Page
+from wagtail.core.models import Locale, Page
 from wagtail.search.backends import get_search_backend
 from wagtail.search.backends.base import FilterFieldError, OrderByFieldError
 
@@ -18,6 +19,10 @@ class FieldsFilter(BaseFilterBackend):
         """
         fields = set(view.get_available_fields(queryset.model, db_fields_only=True))
 
+        # Locale is a database field, but we provide a separate filter for it
+        if 'locale' in fields:
+            fields.remove('locale')
+
         for field_name, value in request.GET.items():
             if field_name in fields:
                 try:
@@ -180,3 +185,16 @@ class DescendantOfFilter(BaseFilterBackend):
             queryset = queryset.descendant_of(parent_page)
 
         return queryset
+
+
+class LocaleFilter(BaseFilterBackend):
+    """
+    Implements the ?locale filter which limits the set of pages to a
+    particular locale.
+    """
+    def filter_queryset(self, request, queryset, view):
+        if 'locale' in request.GET:
+            locale = get_object_or_404(Locale, language_code=request.GET['locale'])
+            queryset = queryset.filter(locale=locale)
+
+        return queryset

wagtail/api/v2/tests/test_pages.py

@@ -8,7 +8,7 @@ from django.test.utils import override_settings
 from django.urls import reverse
 
 from wagtail.api.v2 import signal_handlers
-from wagtail.core.models import Page, Site
+from wagtail.core.models import Locale, Page, Site
 from wagtail.tests.demosite import models
 from wagtail.tests.testapp.models import StreamPage
 
@@ -145,6 +145,21 @@ class TestPageListing(TestCase):
         self.assertEqual(response.status_code, 400)
         self.assertEqual(content, {'message': "type doesn't exist"})
 
+    # LOCALE FILTER
+
+    @override_settings(WAGTAIL_I18N_ENABLED=True)
+    def test_locale_filter(self):
+        french = Locale.objects.create(language_code='fr')
+        homepage = Page.objects.get(depth=2)
+        french_homepage = homepage.copy_for_translation(french)
+        french_homepage.get_latest_revision().publish()
+
+        response = self.get_response(locale='fr')
+        content = json.loads(response.content.decode('UTF-8'))
+
+        self.assertEqual(len(content['items']), 1)
+        self.assertEqual(content['items'][0]['id'], french_homepage.id)
+
     # FIELDS
 
     def test_fields_default(self):

wagtail/api/v2/views.py

@@ -14,7 +14,8 @@ from rest_framework.viewsets import GenericViewSet
 from wagtail.api import APIField
 from wagtail.core.models import Page, Site
 
-from .filters import ChildOfFilter, DescendantOfFilter, FieldsFilter, OrderingFilter, SearchFilter
+from .filters import (
+    ChildOfFilter, DescendantOfFilter, FieldsFilter, LocaleFilter, OrderingFilter, SearchFilter)
 from .pagination import WagtailPagination
 from .serializers import BaseSerializer, PageSerializer, get_serializer_class
 from .utils import (
@@ -367,12 +368,14 @@ class PagesAPIViewSet(BaseAPIViewSet):
         ChildOfFilter,
         DescendantOfFilter,
         OrderingFilter,
-        SearchFilter
+        SearchFilter,
+        LocaleFilter,
     ]
     known_query_parameters = BaseAPIViewSet.known_query_parameters.union([
         'type',
         'child_of',
         'descendant_of',
+        'locale',
     ])
     body_fields = BaseAPIViewSet.body_fields + [
         'title',