Fixed #22404 -- Added a view that exposes i18n catalog as a JSON

Added django.views.i18n.json_catalog() view, which returns a JSON
response containing translations, formats, and a plural expression
for the specified language.

django/views/i18n.py

@@ -17,6 +17,9 @@ from django.utils.translation import (
     LANGUAGE_SESSION_KEY, check_for_language, get_language, to_locale,
 )
 
+DEFAULT_PACKAGES = ['django.conf']
+LANGUAGE_QUERY_PARAMETER = 'language'
+
 
 def set_language(request):
     """
@@ -36,7 +39,7 @@ def set_language(request):
             next = '/'
     response = http.HttpResponseRedirect(next)
     if request.method == 'POST':
-        lang_code = request.POST.get('language')
+        lang_code = request.POST.get(LANGUAGE_QUERY_PARAMETER)
         if lang_code and check_for_language(lang_code):
             next_trans = translate_url(next, lang_code)
             if next_trans != next:
@@ -199,7 +202,7 @@ def get_javascript_catalog(locale, domain, packages):
     default_locale = to_locale(settings.LANGUAGE_CODE)
     app_configs = apps.get_app_configs()
     allowable_packages = set(app_config.name for app_config in app_configs)
-    allowable_packages.add('django.conf')
+    allowable_packages.update(DEFAULT_PACKAGES)
     packages = [p for p in packages if p in allowable_packages]
     t = {}
     paths = []
@@ -284,6 +287,21 @@ def get_javascript_catalog(locale, domain, packages):
     return catalog, plural
 
 
+def _get_locale(request):
+    language = request.GET.get(LANGUAGE_QUERY_PARAMETER)
+    if not (language and check_for_language(language)):
+        language = get_language()
+    return to_locale(language)
+
+
+def _parse_packages(packages):
+    if packages is None:
+        packages = list(DEFAULT_PACKAGES)
+    elif isinstance(packages, six.string_types):
+        packages = packages.split('+')
+    return packages
+
+
 def null_javascript_catalog(request, domain=None, packages=None):
     """
     Returns "identity" versions of the JavaScript i18n functions -- i.e.,
@@ -305,16 +323,35 @@ def javascript_catalog(request, domain='djangojs', packages=None):
     go to the djangojs domain. But this might be needed if you
     deliver your JavaScript source from Django templates.
     """
-    locale = to_locale(get_language())
-
-    if request.GET and 'language' in request.GET:
-        if check_for_language(request.GET['language']):
-            locale = to_locale(request.GET['language'])
-
-    if packages is None:
-        packages = ['django.conf']
-    if isinstance(packages, six.string_types):
-        packages = packages.split('+')
-
+    locale = _get_locale(request)
+    packages = _parse_packages(packages)
     catalog, plural = get_javascript_catalog(locale, domain, packages)
     return render_javascript_catalog(catalog, plural)
+
+
+def json_catalog(request, domain='djangojs', packages=None):
+    """
+    Return the selected language catalog as a JSON object.
+
+    Receives the same parameters as javascript_catalog(), but returns
+    a response with a JSON object of the following format:
+
+        {
+            "catalog": {
+                # Translations catalog
+            },
+            "formats": {
+                # Language formats for date, time, etc.
+            },
+            "plural": '...'  # Expression for plural forms, or null.
+        }
+    """
+    locale = _get_locale(request)
+    packages = _parse_packages(packages)
+    catalog, plural = get_javascript_catalog(locale, domain, packages)
+    data = {
+        'catalog': catalog,
+        'formats': get_formats(),
+        'plural': plural,
+    }
+    return http.JsonResponse(data)

docs/releases/1.9.txt

@@ -357,6 +357,10 @@ Internationalization
   for languages which can be written in different scripts, for example Latin
   and Cyrillic (e.g. ``be@latin``).
 
+* Added the :func:`django.views.i18n.json_catalog` view to help build a custom
+  client-side i18n library upon Django translations. It returns a JSON object
+  containing a translations catalog, formatting settings, and a plural rule.
+
 * Added the ``name_translated`` attribute to the object returned by the
   :ttag:`get_language_info` template tag. Also added a corresponding template
   filter: :tfilter:`language_name_translated`.

docs/topics/i18n/translation.txt

@@ -1213,6 +1213,52 @@ Additionally, if there are complex rules around pluralization, the catalog view
 will render a conditional expression. This will evaluate to either a ``true``
 (should pluralize) or ``false`` (should **not** pluralize) value.
 
+The ``json_catalog`` view
+-------------------------
+
+.. versionadded:: 1.9
+
+.. function:: json_catalog(request, domain='djangojs', packages=None)
+
+In order to use another client-side library to handle translations, you may
+want to take advantage of the ``json_catalog()`` view. It's similar to
+:meth:`~django.views.i18n.javascript_catalog` but returns a JSON response.
+
+The JSON object contains i18n formatting settings (those available for
+`get_format`_), a plural rule (as a ``plural`` part of a GNU gettext
+``Plural-Forms`` expression), and translation strings. The translation strings
+are taken from applications or Django's own translations, according to what is
+specified either via ``urlpatterns`` arguments or as request parameters. Paths
+listed in :setting:`LOCALE_PATHS` are also included.
+
+The view is hooked up to your application and configured in the same fashion as
+:meth:`~django.views.i18n.javascript_catalog` (namely, the ``domain`` and
+``packages`` arguments behave identically)::
+
+    from django.views.i18n import json_catalog
+
+    js_info_dict = {
+        'packages': ('your.app.package',),
+    }
+
+    urlpatterns = [
+        url(r'^jsoni18n/$', json_catalog, js_info_dict),
+    ]
+
+The response format is as follows:
+
+.. code-block:: json
+
+    {
+        "catalog": {
+            # Translations catalog
+        },
+        "formats": {
+            # Language formats for date, time, etc.
+        },
+        "plural": "..."  # Expression for plural forms, or null.
+    }
+
 Note on performance
 -------------------
 

tests/view_tests/tests/test_i18n.py

@@ -105,6 +105,20 @@ class I18NTests(TestCase):
                     # Message with context (msgctxt)
                     self.assertContains(response, '"month name\\u0004May": "mai"', 1)
 
+    def test_jsoni18n(self):
+        """
+        The json_catalog returns the language catalog and settings as JSON.
+        """
+        with override('de'):
+            response = self.client.get('/jsoni18n/')
+            data = json.loads(response.content.decode('utf-8'))
+            self.assertIn('catalog', data)
+            self.assertIn('formats', data)
+            self.assertIn('plural', data)
+            self.assertEqual(data['catalog']['month name\x04May'], 'Mai')
+            self.assertIn('DATETIME_FORMAT', data['formats'])
+            self.assertEqual(data['plural'], '(n != 1)')
+
 
 @override_settings(ROOT_URLCONF='view_tests.urls')
 class JsI18NTests(SimpleTestCase):
@@ -127,6 +141,21 @@ class JsI18NTests(SimpleTestCase):
             response = self.client.get('/jsi18n/')
             self.assertNotContains(response, 'esto tiene que ser traducido')
 
+    def test_jsoni18n_with_missing_en_files(self):
+        """
+        Same as above for the json_catalog view. Here we also check for the
+        expected JSON format.
+        """
+        with self.settings(LANGUAGE_CODE='es'), override('en-us'):
+            response = self.client.get('/jsoni18n/')
+            data = json.loads(response.content.decode('utf-8'))
+            self.assertIn('catalog', data)
+            self.assertIn('formats', data)
+            self.assertIn('plural', data)
+            self.assertEqual(data['catalog'], {})
+            self.assertIn('DATETIME_FORMAT', data['formats'])
+            self.assertIsNone(data['plural'])
+
     def test_jsi18n_fallback_language(self):
         """
         Let's make sure that the fallback language is still working properly

tests/view_tests/urls.py

@@ -84,6 +84,7 @@ urlpatterns = [
     url(r'^jsi18n_admin/$', i18n.javascript_catalog, js_info_dict_admin),
     url(r'^jsi18n_template/$', views.jsi18n),
     url(r'^jsi18n_multi_catalogs/$', views.jsi18n_multi_catalogs),
+    url(r'^jsoni18n/$', i18n.json_catalog, js_info_dict),
 
     # Static views
     url(r'^site_media/(?P<path>.*)$', static.serve, {'document_root': media_dir}),