Fixed #12978 -- Added support for RSS feed stylesheets.

3 files changed, 166 insertions, 8 deletions

diff --git a/docs/ref/contrib/syndication.txt b/docs/ref/contrib/syndication.txt
index d9672c5b00..d0a3cc41f7 100644
--- a/docs/ref/contrib/syndication.txt
+++ b/docs/ref/contrib/syndication.txt
@@ -596,6 +596,24 @@ This example illustrates all possible attributes and methods for a
 
         ttl = 600  # Hard-coded Time To Live.
 
+        # STYLESHEETS -- Optional. To set, provide one of the following three.
+        # The framework looks for them in this order.
+
+        def stylesheets(self, obj):
+            """
+            Takes the object returned by get_object() and returns the feed's
+            stylesheets (as URL strings or as Stylesheet instances).
+            """
+
+        def stylesheets(self):
+            """
+            Returns the feed's stylesheets (as URL strings or Stylesheet
+            instances).
+            """
+
+        # Hardcoded stylesheets.
+        stylesheets = ["/stylesheet1.xsl", "stylesheet2.xsl"]
+
         # ITEMS -- One of the following three is required. The framework looks
         # for them in this order.
 
@@ -961,16 +979,26 @@ They share this interface:
     * ``feed_copyright``
     * ``feed_guid``
     * ``ttl``
+    * ``stylesheets``
 
     Any extra keyword arguments you pass to ``__init__`` will be stored in
     ``self.feed`` for use with `custom feed generators`_.
 
-    All parameters should be strings, except ``categories``, which should be a
-    sequence of strings. Beware that some control characters
-    are `not allowed <https://www.w3.org/International/questions/qa-controls>`_
-    in XML documents. If your content has some of them, you might encounter a
+    All parameters should be strings, except for two:
+
+    * ``categories`` should be a sequence of strings.
+    * ``stylesheets`` should be a sequence of either strings or
+      :class:`~django.utils.feedgenerator.Stylesheet` instances.
+
+    Beware that some control characters are
+    `not allowed <https://www.w3.org/International/questions/qa-controls>`_ in
+    XML documents. If your content has some of them, you might encounter a
     :exc:`ValueError` when producing the feed.
 
+    .. versionchanged:: 5.2
+
+        The ``stylesheets`` argument was added.
+
 :meth:`.SyndicationFeed.add_item`
     Add an item to the feed with the given parameters.
 
@@ -1095,3 +1123,90 @@ For example, you might start implementing an iTunes RSS feed generator like so::
 
 There's a lot more work to be done for a complete custom feed class, but the
 above example should demonstrate the basic idea.
+
+.. _feed-stylesheets:
+
+Feed stylesheets
+----------------
+
+.. versionadded:: 5.2
+
+If you wish to have your RSS feed render nicely in a browser, you will need to
+provide styling information for the XML file, typically in XSLT_ or CSS
+formats.
+
+You can add this to your RSS feed by setting the ``stylesheets`` attribute on
+the feed class.
+
+This can be a hardcoded URL::
+
+    from django.contrib.syndication.views import Feed
+
+
+    class FeedWithHardcodedStylesheet(Feed):
+        stylesheets = [
+            "https://example.com/rss_stylesheet.xslt",
+        ]
+
+You can also use Django's static files system::
+
+    from django.contrib.syndication.views import Feed
+    from django.templatetags.static import static
+
+
+    class FeedWithStaticFileStylesheet(Feed):
+        stylesheets = [
+            static("rss_styles.xslt"),
+        ]
+
+Another option is to have a view in your project that renders the XSLT
+document. You can then link it like so::
+
+    from django.contrib.syndication.views import Feed
+    from django.urls import reverse_lazy
+
+
+    class FeedWithStylesheetView(Feed):
+        stylesheets = [
+            reverse_lazy("your-custom-view-name"),
+        ]
+
+Django will normally try to guess the MIME type of the given URL based on its
+extension, but if that fails you can specify it using the
+:class:`~django.utils.feedgenerator.Stylesheet` class::
+
+    from django.contrib.syndication.views import Feed
+    from django.utils.feedgenerator import Stylesheet
+
+
+    class FeedWithHardcodedStylesheet(Feed):
+        stylesheets = [
+            Stylesheet("https://example.com/rss_stylesheet", mimetype="text/xsl"),
+        ]
+
+Similarly, if you'd like to use a different ``media`` attribute than ``screen``
+(Django's default), you can use the
+:class:`~django.utils.feedgenerator.Stylesheet` class again::
+
+    from django.contrib.syndication.views import Feed
+    from django.utils.feedgenerator import Stylesheet
+
+
+    class FeedWithHardcodedStylesheet(Feed):
+        stylesheets = [
+            Stylesheet("https://example.com/rss_stylesheet.xslt", media="print"),
+        ]
+
+Any of these options can be combined when using multiple stylesheets::
+
+    from django.contrib.syndication.views import Feed
+    from django.utils.feedgenerator import Stylesheet
+
+
+    class MultiStylesheetFeed(Feed):
+        stylesheets = [
+            "/stylesheet1.xsl",
+            Stylesheet("/stylesheet2.xsl"),
+        ]
+
+.. _xslt: https://developer.mozilla.org/en-US/docs/Web/XSLT/Transforming_XML_with_XSLT
diff --git a/docs/ref/utils.txt b/docs/ref/utils.txt
index 3e357cba17..9fb1e83e9e 100644
--- a/docs/ref/utils.txt
+++ b/docs/ref/utils.txt
@@ -331,6 +331,32 @@ https://web.archive.org/web/20110718035220/http://diveintomark.org/archives/2004
 
     See https://web.archive.org/web/20110514113830/http://diveintomark.org/archives/2004/05/28/howto-atom-id
 
+``Stylesheet``
+--------------
+
+.. versionadded:: 5.2
+
+.. class:: Stylesheet(url, mimetype="", media="screen")
+
+    Represents an RSS stylesheet.
+
+    .. attribute:: url
+
+        Required argument. The URL where the stylesheet is located.
+
+    .. attribute:: mimetype
+
+        An optional string containing the MIME type of the stylesheet. If not
+        specified, Django will attempt to guess it by using Python's
+        :py:func:`mimetypes.guess_type()`. Use ``mimetype=None`` if you don't
+        want your stylesheet to have a MIME type specified.
+
+    .. attribute:: media
+
+        An optional string which will be used as the ``media`` attribute of
+        the stylesheet. Defaults to ``"screen"``. Use ``media=None`` if you
+        don't want your stylesheet to have a ``media`` attribute.
+
 ``SyndicationFeed``
 -------------------
 
@@ -339,7 +365,7 @@ https://web.archive.org/web/20110718035220/http://diveintomark.org/archives/2004
     Base class for all syndication feeds. Subclasses should provide
     ``write()``.
 
-    .. method:: __init__(title, link, description, language=None, author_email=None, author_name=None, author_link=None, subtitle=None, categories=None, feed_url=None, feed_copyright=None, feed_guid=None, ttl=None, **kwargs)
+    .. method:: __init__(title, link, description, language=None, author_email=None, author_name=None, author_link=None, subtitle=None, categories=None, feed_url=None, feed_copyright=None, feed_guid=None, ttl=None, stylesheets=None, **kwargs)
 
         Initialize the feed with the given dictionary of metadata, which applies
         to the entire feed.
@@ -347,8 +373,15 @@ https://web.archive.org/web/20110718035220/http://diveintomark.org/archives/2004
         Any extra keyword arguments you pass to ``__init__`` will be stored in
         ``self.feed``.
 
-        All parameters should be strings, except ``categories``, which should
-        be a sequence of strings.
+        All parameters should be strings, except for two:
+
+        * ``categories`` should be a sequence of strings.
+        * ``stylesheets`` should be a sequence of either strings or
+          :class:`Stylesheet` instances.
+
+        .. versionchanged:: 5.2
+
+            The ``stylesheets`` argument was added.
 
     .. method:: add_item(title, link, description, author_email=None, author_name=None, author_link=None, pubdate=None, comments=None, unique_id=None, categories=(), item_copyright=None, ttl=None, updateddate=None, enclosures=None, **kwargs)
 
@@ -368,6 +401,13 @@ https://web.archive.org/web/20110718035220/http://diveintomark.org/archives/2004
         Add elements in the root (i.e. feed/channel) element.
         Called from ``write()``.
 
+    .. method:: add_stylesheets(self, handler)
+
+        .. versionadded:: 5.2
+
+        Add stylesheet information to the document.
+        Called from ``write()``.
+
     .. method:: item_attributes(item)
 
         Return extra attributes to place on each item (i.e. item/entry)
diff --git a/docs/releases/5.2.txt b/docs/releases/5.2.txt
index 0a0cfb0aef..e0f190076a 100644
--- a/docs/releases/5.2.txt
+++ b/docs/releases/5.2.txt
@@ -100,7 +100,10 @@ Minor features
 :mod:`django.contrib.syndication`
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-* ...
+* All :class:`~django.utils.feedgenerator.SyndicationFeed` classes now support
+  a ``stylesheets`` attribute. If specified, an ``<? xml-stylesheet ?>``
+  processing instruction will be added to the top of the document for each
+  stylesheet in the given list. See :ref:`feed-stylesheets` for more details.
 
 Asynchronous views
 ~~~~~~~~~~~~~~~~~~