~launchpad-pqm/launchpad/devel

= Canonical URLs =

https://launchpad.canonical.com/CanonicalUrls

== The browser:url ZCML directive ==

The browser:url directive registers an ICanonicalUrlData adapter.

In this test, we'll use a URL hierarchy /countries/England/+towns/London

In this test, we'll use interfaces ICountrySet, ICountry and ITown, which we
will put in lp.testing.

    >>> from lp.services.webapp.interfaces import ICanonicalUrlData
    >>> from zope.interface import Interface, Attribute, implements

    >>> class ICountrySet(Interface):
    ...     pass

    >>> class ICountry(Interface):
    ...     name = Attribute('the name of this country')

    >>> class ITown(Interface):
    ...     """Dummy interface for use in browser:url tests."""
    ...     country = Attribute('the country the town is in')
    ...     name = Attribute('the name of this town')

Add a view for Country/+map.

    >>> from zope.component import provideAdapter
    >>> from zope.publisher.interfaces.browser import IDefaultBrowserLayer
    >>> class CountryMapView(object):
    ...     def __init__(self, country, request):
    ...         pass
    >>> provideAdapter(CountryMapView, (ICountry, IDefaultBrowserLayer),
    ...                name='+map', provides=Interface)

Define a navigation for the Country URL.

    >>> from lp.services.webapp.publisher import (
    ...     Navigation, redirection, stepto, stepthrough)
    >>> from zope.publisher.interfaces.browser import IBrowserPublisher
    >>> class CountryNavigation(Navigation):
    ...     redirection('+capital', '+towns/London')
    ...
    ...     @stepthrough('+towns')
    ...     def stepthrown_town(self, name):
    ...         if name == 'London':
    ...             return town_instance
    ...         else:
    ...             return None
    ...
    ...     @stepto('+greenwich')
    ...     def stepto_greenwhich(self):
    ...         town = Town()
    ...         town.name = 'Greenwich'
    ...         return town
    >>> provideAdapter(
    ...     CountryNavigation, [ICountry, IDefaultBrowserLayer], 
    ...     IBrowserPublisher)

Put the interfaces into lp.testing, ensuring that there
are not already objects with those names there.

    >>> import lp.testing
    >>> for interface in ICountrySet, ICountry, ITown:
    ...     name = interface.getName()
    ...     assert getattr(lp.testing, name, None) is None
    ...     setattr(lp.testing, name, interface)
    ...     interface.__module__ = 'lp.testing'

We don't have ICanonicalUrlData adapters for objects that provide any of these
interfaces.  First, we create some countryset, country and town objects.

    >>> class CountrySet:
    ...     implements(ICountrySet)
    >>> countryset_instance = CountrySet()

    >>> class Country:
    ...    implements(ICountry)
    ...    name = 'England'
    >>> country_instance = Country()

    >>> class Town:
    ...     implements(ITown)
    ...     country = country_instance
    ...     name = 'London'
    >>> town_instance = Town()

Next, we check there are no ICanonicalUrlData adapters for these objects.

    >>> for obj in countryset_instance, country_instance, town_instance:
    ...     assert ICanonicalUrlData(obj, None) is None

Configure a browser:url for ITown.  Our first attempt fails because we mistyped
'countryOopsTypo', and there is no such name in ITown.

    >>> from zope.configuration import xmlconfig
    >>> zcmlcontext = xmlconfig.string("""
    ... <configure xmlns:browser="http://namespaces.zope.org/browser">
    ...   <include file="lib/lp/services/webapp/meta.zcml" />
    ...   <browser:url
    ...       for="lp.testing.ITown"
    ...       path_expression="string:+towns/${name}"
    ...       attribute_to_parent="countryOopsTypo"
    ...       />
    ... </configure>
    ... """)
    Traceback (most recent call last):
    ...
    ZopeXMLConfigurationError: File "<string>", line ...
        AttributeError: The name "countryOopsTypo" is not in lp.testing.ITown

    >>> zcmlcontext = xmlconfig.string("""
    ... <configure xmlns:browser="http://namespaces.zope.org/browser">
    ...   <include file="lib/lp/services/webapp/meta.zcml" />
    ...   <browser:url
    ...       for="lp.testing.ITown"
    ...       path_expression="string:+towns/${name}"
    ...       attribute_to_parent="country"
    ...       />
    ... </configure>
    ... """)

Now, there is an ICanonicalUrlData registered for ITown.

    >>> town_urldata = ICanonicalUrlData(town_instance)
    >>> from lp.services.webapp.testing import verifyObject
    >>> verifyObject(ICanonicalUrlData, town_urldata)
    True
    >>> town_urldata.path
    u'+towns/London'
    >>> town_urldata.inside is country_instance
    True

The parent of an object might be accessible via an attribute, or it might
be a utility.  This is the case for an ICountry object: its parent is the
ICountrySet.  I need to put the countryset_instance somewhere we can get
at it from zcml.  I'll put it in lp.testing.

    >>> assert getattr(
    ...     lp.testing, 'countryset_instance', None) is None

    >>> lp.testing.countryset_instance = countryset_instance

    >>> zcmlcontext = xmlconfig.string("""
    ... <configure
    ...     xmlns="http://namespaces.zope.org/zope"
    ...     xmlns:browser="http://namespaces.zope.org/browser">
    ...   <include file="lib/lp/services/webapp/meta.zcml" />
    ...   <configure package="zope.app.component">
    ...       <include file="meta.zcml" />
    ...   </configure>
    ...   <utility
    ...       provides="lp.testing.ICountrySet"
    ...       component="lp.testing.countryset_instance"
    ...       />
    ...   <browser:url
    ...       for="lp.testing.ICountry"
    ...       path_expression="name"
    ...       parent_utility="lp.testing.ICountrySet"
    ...       />
    ... </configure>
    ... """)

Now, there is an ICanonicalUrlData registered for ICountry.

    >>> country_urldata = ICanonicalUrlData(country_instance)
    >>> from lp.services.webapp.testing import verifyObject
    >>> verifyObject(ICanonicalUrlData, country_urldata)
    True
    >>> country_urldata.path
    'England'
    >>> country_urldata.inside is countryset_instance
    True

We need to specify a browser:url for ICountrySet.  We'll use a variation on
the zcml that allows us to directly set an ICanonicalUrlData adapter to use.
The adapter will make its parent the ILaunchpadRoot utility.  This is not the
normal way to do this.  Normally, we'd just say

  parent_utility="lp.services.webapp.interfaces.ILaunchpadRoot"

But, here, I want to test the variant of the zcml directive that specifes
an adapter.

    >>> from lp.services.webapp.interfaces import ILaunchpadRoot
    >>> class CountrySetUrl:
    ...
    ...     implements(ICanonicalUrlData)
    ...
    ...     def __init__(self, context):
    ...         self.context = context
    ...
    ...     path = 'countries'
    ...
    ...     rootsite = None
    ...
    ...     @property
    ...     def inside(self):
    ...         return getUtility(ILaunchpadRoot)

The CountrySetUrl class needs to be accessible from zcml.  So, we put it
in lp.testing.

    >>> lp.testing.CountrySetUrl = CountrySetUrl

    >>> zcmlcontext = xmlconfig.string("""
    ... <configure xmlns:browser="http://namespaces.zope.org/browser">
    ...   <include file="lib/lp/services/webapp/meta.zcml" />
    ...   <browser:url
    ...       for="lp.testing.ICountrySet"
    ...       urldata="lp.testing.CountrySetUrl"
    ...       />
    ... </configure>
    ... """)

Now, there is an ICanonicalUrlData registered for ICountrySet.

    >>> countryset_urldata = ICanonicalUrlData(countryset_instance)
    >>> from lp.services.webapp.testing import verifyObject
    >>> verifyObject(ICanonicalUrlData, countryset_urldata)
    True
    >>> countryset_urldata.path
    'countries'
    >>> countryset_urldata.inside is getUtility(ILaunchpadRoot)
    True


== The Launchpad root object ==

The ILaunchpadRoot object has its own ICanonicalUrlData adapter.

    >>> root_urldata = ICanonicalUrlData(getUtility(ILaunchpadRoot))
    >>> verifyObject(ICanonicalUrlData, root_urldata)
    True
    >>> root_urldata.path
    ''
    >>> root_urldata.inside is None
    True


== The canonical_url function ==

The canonical_url function gives you the canonical URL for an object, by
stitching together the various ICanonicalUrlData adapters for that object
and the objects it is inside of (or in other words, hierarchically below).

    >>> from lp.services.webapp import canonical_url
    >>> canonical_url(getUtility(ILaunchpadRoot))
    u'http://launchpad.dev/'
    >>> canonical_url(countryset_instance)
    u'http://launchpad.dev/countries'
    >>> canonical_url(country_instance)
    u'http://launchpad.dev/countries/England'
    >>> canonical_url(town_instance)
    u'http://launchpad.dev/countries/England/+towns/London'

We can see that this is the mainsite rooturl as configured in launchpad.conf.

    >>> from lp.services.webapp.vhosts import allvhosts
    >>> print allvhosts.configs['mainsite'].rooturl
    http://launchpad.dev/

If anywhere in the chain we have an object that cannot be adapted to
ICanonicalUrlData, a NoCanonicalUrl error is raised.

The next few lines tests the case where the object you want a URL for cannot
itself be adapted to ICanonicalUrlData.

    >>> object_that_has_no_url = object()
    >>> canonical_url(object_that_has_no_url)
    Traceback (most recent call last):
    ...
    NoCanonicalUrl: No url for <...object at ...> because <...object at ...> broke the chain.

Now, we must test the case where the object can be adapted to
ICanonicalUrlData, but its parent or its parent's parent (and so on) cannot.

    >>> class ObjectThatHasUrl:
    ...     implements(ICanonicalUrlData)
    ...     def __init__(self, name, parent):
    ...         self.path = name
    ...         self.inside = parent
    >>> unrooted_object = ObjectThatHasUrl('unrooted', object_that_has_no_url)
    >>> canonical_url(unrooted_object)
    Traceback (most recent call last):
    ...
    NoCanonicalUrl: No url for <...ObjectThatHasUrl...> because <...object...> broke the chain.

The first argument to NoCanonicalUrl is the object that a canonical url was
requested for.  The second argument is the object that broke the chain.

== The canonical_urldata_iterator function ==

TODO.  Currently tested implicitly by the canonical_url_iterator tests.


== The canonical_url_iterator function ==

The canonical_url_iterator function is not available from .webapp because
it won't be used in the general application, just by parts of the webapp
systems.

    >>> from lp.services.webapp.publisher import canonical_url_iterator

First, let's define a helper function to help us test canonical_url_iterator.

    >>> def print_url_iterator(obj):
    ...     for obj in canonical_url_iterator(obj):
    ...         print obj.__class__.__name__

    >>> print_url_iterator(getUtility(ILaunchpadRoot))
    RootObject

    >>> print_url_iterator(countryset_instance)
    CountrySet
    RootObject

    >>> print_url_iterator(country_instance)
    Country
    CountrySet
    RootObject

We have to do the tests that involve errors bit by bit, to allow the doctest
to work properly.

    >>> iterator = canonical_url_iterator(object_that_has_no_url)
    >>> iterator.next().__class__.__name__
    'object'
    >>> iterator.next()
    Traceback (most recent call last):
    ...
    NoCanonicalUrl: No url for <...object...> because <...object...> broke the chain.

    >>> iterator = canonical_url_iterator(unrooted_object)
    >>> iterator.next().__class__.__name__
    'ObjectThatHasUrl'
    >>> iterator.next().__class__.__name__
    'object'
    >>> iterator.next()
    Traceback (most recent call last):
    ...
    NoCanonicalUrl: No url for <...ObjectThatHasUrl...> because <...object...> broke the chain.


== canonical_url and requests ==

You can pass an http request object into canonical_url as its optional
second argument.  This tells canonical_url to use the protocol, host and port
from the request.  To get this information, canonical_url uses the operation
getApplicationURL() from
zope.publisher.interfaces.http.IHTTPApplicationRequest.

    >>> from zope.publisher.interfaces.http import IHTTPApplicationRequest
    >>> class FakeRequest:
    ...
    ...     implements(IHTTPApplicationRequest)
    ...
    ...     def __init__(self, applicationurl):
    ...         self.applicationurl = applicationurl
    ...         self.interaction = None
    ...
    ...     def getRootURL(self, rootsite):
    ...         if rootsite is not None:
    ...             return allvhosts.configs[rootsite].rooturl
    ...         else:
    ...             return self.getApplicationURL() + '/'
    ...
    ...     def getApplicationURL(self, depth=0, path_only=False):
    ...         assert depth == 0, 'this is not a real IHTTPApplicationRequest'
    ...         assert not path_only, 'not a real IHTTPApplicationRequest'
    ...         return self.applicationurl

    >>> mandrill_request = FakeRequest('https://mandrill.example.org:23')
    >>> canonical_url(country_instance)
    u'http://launchpad.dev/countries/England'
    >>> canonical_url(country_instance, mandrill_request)
    u'https://mandrill.example.org:23/countries/England'

However, if we log in, then that request should be used when none is explicitly
given otherwise.

    >>> sesame_request = FakeRequest('http://muppet.example.com')
    >>> login(ANONYMOUS, sesame_request)
    >>> canonical_url(country_instance)
    u'http://muppet.example.com/countries/England'
    >>> canonical_url(country_instance, mandrill_request)
    u'https://mandrill.example.org:23/countries/England'


== canonical_url and overriding rootsite ==

The optional parameter rootsite on the canonical_url function can be
used to 'force' the url to a different rootsite.  Providing a rootsite
overrides the rootsite defined by either the object or the request.

Here is the current country instance without the ICanonicalUrlData specifying
a rootsite.

Overriding the rootsite from the default request:

    >>> canonical_url(country_instance)
    u'http://muppet.example.com/countries/England'
    >>> canonical_url(country_instance, rootsite='code')
    u'http://code.launchpad.dev/countries/England'

Overriding the rootsite from the specified request:

    >>> canonical_url(country_instance, mandrill_request)
    u'https://mandrill.example.org:23/countries/England'
    >>> canonical_url(country_instance, mandrill_request, rootsite='code')
    u'http://code.launchpad.dev/countries/England'

And if the configuration does provide a rootsite:

    >>> zcmlcontext = xmlconfig.string("""
    ... <configure
    ...     xmlns="http://namespaces.zope.org/zope"
    ...     xmlns:browser="http://namespaces.zope.org/browser">
    ...   <include file="lib/lp/services/webapp/meta.zcml" />
    ...   <configure package="zope.app.component">
    ...       <include file="meta.zcml" />
    ...   </configure>
    ...   <utility
    ...       provides="lp.testing.ICountrySet"
    ...       component="lp.testing.countryset_instance"
    ...       />
    ...   <browser:url
    ...       for="lp.testing.ICountry"
    ...       path_expression="name"
    ...       parent_utility="lp.testing.ICountrySet"
    ...       rootsite="bugs"
    ...       />
    ... </configure>
    ... """)

    >>> canonical_url(country_instance)
    u'http://bugs.launchpad.dev/countries/England'
    >>> canonical_url(country_instance, rootsite='code')
    u'http://code.launchpad.dev/countries/England'
    >>> canonical_url(country_instance, mandrill_request, rootsite='code')
    u'http://code.launchpad.dev/countries/England'


== canonical_url and named views ==

The url for a particular view of an object can be generated by specifying
the view's name.

    >>> canonical_url(country_instance, view_name="+map")
    u'http://bugs.launchpad.dev/countries/England/+map'

view_name also works when the view_name refers to a Navigation stepto,
stepthrough, or redirection:

    >>> canonical_url(country_instance, view_name="+greenwich")
    u'http://bugs.launchpad.dev/countries/England/+greenwich'

    >>> canonical_url(country_instance, view_name="+capital")
    u'http://bugs.launchpad.dev/countries/England/+capital'

    >>> canonical_url(country_instance, view_name="+towns")
    u'http://bugs.launchpad.dev/countries/England/+towns'

Giving an unregistered view name will trigger an assertion failure.

    >>> canonical_url(country_instance, view_name="+does-not-exist")
    Traceback (most recent call last):
      ...
    AssertionError: Name "+does-not-exist" is not registered as a view 
    or navigation step for "Country" on "bugs".


== The 'nearest' helper function ==

The `nearest(obj, *interfaces)` function returns the nearest object up the
canonical url chain that provides at least one of the interfaces given.

    >>> from lp.services.webapp import nearest
    >>> from lp.registry.interfaces.person import IPerson
    >>> nearest(town_instance, IPerson) is None
    True
    >>> nearest(town_instance, ITown) is town_instance
    True
    >>> nearest(town_instance, IPerson, ITown) is town_instance
    True
    >>> nearest(town_instance, ICountry) is country_instance
    True
    >>> print nearest(unrooted_object, ICountry)
    None


== canonical_url in the web service ==

canonical_url() is sometimes used in code that doesn't have direct
access to the current request, and always wants a URL that can be used
in a browser (for example e-mail notifications or XHTML representations
of objects). Therefore, if no request is explicitly given,
canonical_url() returns the browser URL, even if the current request is
a web service request

    >>> from zope.app.security.principalregistry import (
    ...     UnauthenticatedPrincipal)
    >>> from lp.services.webapp.interaction import setupInteraction
    >>> from lp.services.webapp.servers import WebServiceTestRequest
    >>> from lazr.restful.utils import get_current_browser_request
    >>> anonymous = UnauthenticatedPrincipal(None, None, None)
    >>> api_request = WebServiceTestRequest()
    >>> setupInteraction(anonymous, participation=api_request)
    >>> get_current_browser_request() is api_request
    True

    >>> canonical_url(countryset_instance)
    u'http://launchpad.dev/countries'


If an URL that can be used in the web service is required, a web service
request has to be passed in explicitly.

    >>> canonical_url(countryset_instance, request=api_request)
    u'http://api.launchpad.dev/countries'

It is often the case that the web application wants to provide URLs that will
be written out onto the pages that the Javascript can process using the
LP.client code to get access to the object entries using the API.  In these
cases, the "force_local_path" parameter can be passed to canonical_url to have
only the relative local path returned.

    >>> canonical_url(countryset_instance, force_local_path=True)
    u'/countries'


== The end ==

We've finished with our interfaces and utility component, so remove them from
lp.testing.

    >>> for name in ['ICountrySet', 'ICountry', 'ITown', 'countryset_instance',
    ...              'CountrySetUrl']:
    ...     delattr(lp.testing, name)