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.

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
 -------------------