Merge lp:~leonardr/lazr.restful/version-specific-request-interface into lp:lazr.restful

This branch changes the way an incoming web service request is associated with a specific version of the web service. Previously, the version number was stuffed into a Zope annotation on the request object. Versioned lookups were done as named lookups using the version number as the name.

Now, the web service is expected to define a marker interface for every version it publishes, eg. IWebServiceRequestBeta. Once the traversal code knows which version of the web service the client is requesting, it calls alsoProvides on the request object to mark it with the appropriate marker interface.

The idea here is to get rid of named lookups. Instead of this:

getAdapter(data_model_object, IEntry, name="1.0")

We can now do this:

getMultiAdapter([data_model_object, request], IEntry)

Unfortunately, the benefits of this are mostly in the future. The two named lookups we do right now cannot be turned into multiadapter lookups. The first is the lookup that gets us the version-specific request interface in the first place. The second is a utility lookup:

root = getUtility(IWebServiceRootResource, name="1.0")

There's no such thing as a multi-value utility lookup. However, I'm considering writing a wrapper class that lets the utility lookup look like a simple adaptation:

root = IWebServiceRootResource(request)

But I'm not sure if that's valuable to the programmer.

To avoid a million test failures, I preserved the behavior of the unversioned code (where the incoming request does not have any special interface applied to it). I'll almost certainly remove this code once I make the service generation code support multi-versioning, but that's a way in the future.

Because this branch is complicated and I'm not yet certain it will pay off, I don't plan to land it immediately. Instead, I'll be merging other branches into it and landing the whole thing once I have something useful.

Hi Leonard,

Nice to see this coming along.

This is good to go once you fix the conflit marker and handle my few other
comments.

Cheers

> === modified file 'src/lazr/restful/docs/multiversion.txt'
> --- src/lazr/restful/docs/multiversion.txt 2009-11-19 16:43:08 +0000
> +++ src/lazr/restful/docs/multiversion.txt 2010-01-06 17:40:25 +0000
> @@ -5,10 +5,99 @@
> services. Typically these different services represent successive
> versions of a single web service, improved over time.
>
> +Setup
> +=====
> +
> +First, let's set up the web service infrastructure. Doing this first
> +will let us create HTTP requests for different versions of the web
> +service. The first step is to make all component lookups use the
> +global site manager.
> +
> + >>> from zope.component import getSiteManager
> + >>> sm = getSiteManager()
> +
> + >>> from zope.component import adapter
> + >>> from zope.component.interfaces import IComponentLookup
> + >>> from zope.interface import implementer, Interface
> + >>> @implementer(IComponentLookup)
> + ... @adapter(Interface)
> + ... def everything_uses_the_global_site_manager(context):
> + ... return sm
> + >>> sm.registerAdapter(everything_uses_the_global_site_manager)

Like discussed on IRC, the waving of this dead chicken isn't needed :-)

> +
> +Defining the request interfaces
> +-------------------------------
> +
> +Every version must have a corresponding subclass of
> +IWebServiceClientRequest. These marker interfaces let lazr.restful
> +keep track of which version of the web service a particular client
> +wants to use. In a real application, these interfaces will be
> +generated and registered automatically.
> +
> + >>> from lazr.restful.interfaces import (
> + ... IVersionedClientRequestImplementation, IWebServiceClientRequest)
> + >>> class IWebServiceRequestBeta(IWebServiceClientRequest):
> + ... pass
> +
> + >>> class IWebServiceRequest10(IWebServiceClientRequest):
> + ... pass
> +
> + >>> class IWebServiceRequestDev(IWebServiceClientRequest):
> + ... pass
> +
> + >>> request_classes = [IWebServiceRequestBeta,
> + ... IWebServiceRequest10, IWebServiceRequestDev]
> +
> + >>> from zope.interface import alsoProvides
> + >>> for cls, version in ((IWebServiceRequestBeta, 'beta'),
> + ... (IWebServiceRequest10, '1.0'),
> + ... (IWebServiceRequestDev, 'dev')):
> + ... alsoProvides(cls, IVersionedClientRequestImplementation)
> + ... sm.registerUtility(cls, IVersionedClientRequestImplementation,
> + ... name=version)
> +

Can you explain the use of IVersionedClientRequestImplementation? You
explained on IRC that it to make it easy to retrieve the interface related to
a version string.

Would IVersionedWebClientRequestFactory be a better name?

> +<<<<<<< TREE
> >>> for version in ['beta', 'dev', '1.0']:
> ... sm.registerAdapter(
> ... ContactCollection, provided=ICollection, name=version)
> @@ -397,3 +495,105 @@
> >>> print absoluteURL(dev_app, dev_request)
> http://api.multiversion.dev/d...

I removed the rubber chicken and changed the text in the section on named utilities to make it more clear. I did this in the second branch because this branch has a lot of test failures (which the job of the second branch is to fix). The second branch already included a doctest of request.version, in the "Request lifecycle" section of multiversion.txt.