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= Feeds components =
`feeds` is a ZCML directive for handling feeds requests. The
directive requires minimal ZCML configuration and relies on
implementing view classes defining the `usedfor` and `name` class
variables.
Feeds are defined on the `FeedsLayer` layer.
== Demonstrating a feeds class ==
In order to demonstrate a feed class, we need to create an interface
for the thing comprising the feed. Rather than use a standard
Launchpad interface, we'll define one here.
>>> from zope.interface import Interface, Attribute, implements
>>> from lp.services.feeds.tests.helper import (
... IThing, Thing, ThingFeedView)
== ZCML for browser:feeds ==
The zcml `browser:feeds` directive describes a feed view.
>>> from zope.configuration import xmlconfig
>>> zcmlcontext = xmlconfig.string("""
... <configure xmlns:browser="http://namespaces.zope.org/browser">
... <include package="lp.services.webapp" file="meta.zcml" />
... <include package="zope.app.zcmlfiles" file="meta.zcml" />
... <browser:feeds
... module="lp.services.feeds.tests.helper"
... classes="ThingFeedView"
... />
... </configure>
... """)
Get the view from a `thing` on 'thing-feed' for a request.
>>> from zope.component import getMultiAdapter
>>> from lp.services.webapp.servers import LaunchpadTestRequest
>>> from lp.services.webapp.testing import verifyObject
>>> request = LaunchpadTestRequest()
To successfully get a view, the lookup must be on an object that is an
`IThing` and the view name must be one that is supported. If the
view is not found a ComponentLookupError is raised. Also, the request
must be in the FeedsLayer.
The request we just created is not in the FeedsLayer, so the view will
not be found.
>>> thing = Thing('thing 1')
>>> verifyObject(IThing, thing)
True
>>> feed_view = getMultiAdapter((thing, request), name='thing-feed.xml')
Traceback (most recent call last):
...
ComponentLookupError: ...
Set the layer on the request for all subsequent uses.
>>> from lp.layers import setFirstLayer, FeedsLayer
>>> setFirstLayer(request, FeedsLayer)
If the context object is not an IThing then the view will not be
found.
>>> thing = object()
>>> verifyObject(IThing, thing)
Traceback (most recent call last):
...
DoesNotImplement: ...
>>> feed_view = getMultiAdapter((thing, request), name='thing-feed.atom')
Traceback (most recent call last):
...
ComponentLookupError: ...
If the name is not one of the supported names the view will not be
found.
>>> thing = Thing('thing 1')
>>> verifyObject(IThing, thing)
True
>>> feed_view = getMultiAdapter((thing, request), name='thing-feed.xml')
Traceback (most recent call last):
...
ComponentLookupError: ...
If the thing is an IThing and the name is supported the view will be
found, indicated by the absence of a ComponentLookupError.
>>> thing = Thing('thing 1')
>>> verifyObject(IThing, thing)
True
>>> for name in ['thing-feed.atom', 'thing-feed.html']:
... feed_view = getMultiAdapter((thing, request), name=name)
... print feed_view()
a feed view on an IThing
a feed view on an IThing
== Feeds Configuration Options ==
The max_feed_cache_minutes and the max_bug_feed_cache_minutes
configurations are provided to allow overriding the Expires
and Cache-Control headers so that the feeds will be cached longer
by browsers and the reverse-proxy in front of the feeds servers.
>>> from lp.services.config import config
>>> from canonical.lazr.feed.feed import FeedBase
>>> from lp.bugs.feed.bug import BugsFeedBase
>>> config.launchpad.max_feed_cache_minutes
60
>>> config.launchpad.max_bug_feed_cache_minutes
30
>>> FeedBase.max_age
3600
>>> BugsFeedBase.max_age
1800
>>> config.launchpad.max_feed_cache_minutes * 60 == FeedBase.max_age
True
>>> (config.launchpad.max_bug_feed_cache_minutes * 60
... == BugsFeedBase.max_age)
True
== FeedTypedData class ==
The FeedTypedData class performs the appropriate escaping for data
with a type of "text", "html", or "xhtml". The template is responsible
for setting the "type" attribute in the <title> or <content> element. If
no content type is specified, then "text" is assumed.
Since plain text and html are not valid xml, "<", ">", and "&" must
be escaped using xml entities such as "<".
>>> from canonical.lazr.feed.feed import FeedTypedData
>>> text = FeedTypedData("<b> and and &")
>>> text.content
'<b> and &nbsp; and &amp;'
>>> text2 = FeedTypedData("<b> and and &", content_type="text")
>>> text2.content
'<b> and &nbsp; and &amp;'
>>> html = FeedTypedData("<b> and and &", content_type="html")
>>> html.content
'<b> and &nbsp; and &amp;'
Since xhtml is valid xml, the "<" and ">" characters do not need to be
escaped. However, xhtml supports many more entities than xml, and Internet
Explorer 7 does not allow a DTD to be specified in feeds which prevents the
xhtml entities from easily being registered in the xml document. Therefore,
the xhtml entities will be converted to valid UTF-8. Since some simplistic
feed readers may expect ascii, we prefer using "html" over "xhtml", however,
we are testing xhtml encoding here in case we need it in the future.
>>> xhtml = FeedTypedData("<b> and and &</b><hr/>",
... content_type="xhtml")
>>> xhtml.content
u'<b> and \xa0 and &</b><hr />'
== validate_feed() helper function ==
Pagetests can use the validate_feed() function to perform all the
checks available at http://feedvalidator.org
Occasionally, there will be suggestions from feedvalidator that we will
ignore. For example, when the <title type="text"> element contains html,
we want to view the html as opposed to having the title text formatted.
Therefore, we won't set type="html" for the title element.
>>> feed = """<?xml version="1.0" encoding="UTF-8"?>
... <feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
... <id>one</id>
... <title>Bugs in Launchpad itself</title>
... <link rel="self" href="http://foo.bar" />
... <updated>2006-05-19T06:37:40.344941+00:00</updated>
... <entry>
... <id>http://launchpad.dev/entry</id>
... <author></author>
... <updated>2007-05-19T06:37:40.344941+00:00</updated>
... <title type="text"><b>hello</b></title>
... <content type="html"><b>hello</b></content>
... </entry>
... </feed>"""
>>> from lp.services.feeds.tests.helper import validate_feed
>>> validate_feed(feed, '/atom+xml', 'http://ubuntu.com')
-------- Error: InvalidFullLink --------
Backupcolumn: 7
Backupline: 3
Column: 7
Element: id
Line: 3
Parent: feed
Value: one
=
1: <?xml version="1.0" encoding="UTF-8"?>
2: <feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
3: <id>one</id>
: ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
4: <title>Bugs in Launchpad itself</title>
5: <link rel="self" href="http://foo.bar" />
=
-------- Error: MissingElement --------
Backupcolumn: 12
Backupline: 9
Column: 12
Element: name
Line: 9
Parent: author
=
7: <entry>
8: <id>http://launchpad.dev/entry</id>
9: <author></author>
: ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
10: <updated>2007-05-19T06:37:40.344941+00:00</updated>
11: <title type="text"><b>hello</b></title>
=
-------- Warning: UnexpectedContentType --------
Contenttype: /atom+xml
Type: Feeds
-------- Warning: SelfDoesntMatchLocation --------
Backupcolumn: 41
Backupline: 5
Column: 41
Element: href
Line: 5
Parent: feed
Location: http://ubuntu.com
=
3: <id>one</id>
4: <title>Bugs in Launchpad itself</title>
5: <link rel="self" href="http://foo.bar" />
: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
6: <updated>2006-05-19T06:37:40.344941+00:00</updated>
7: <entry>
=
-------- Warning: ContainsUndeclaredHTML --------
Backupcolumn: 47
Backupline: 11
Column: 47
Element: title
Line: 11
Parent: entry
Value: b
=
9: <author></author>
10: <updated>2007-05-19T06:37:40.344941+00:00</updated>
11: <title type="text"><b>hello</b></title>
: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
12: <content type="html"><b>hello</b></content>
13: </entry>
=
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