A few of us (Alec Mitchell, Godefroid Chapelle, Balazs Ree, Rocky Burt, Daniel Nouri, Rob Miller, Vincenzo Di Somma, and myself) have been discussing this in depth at the Sorrento Sprint. We've reached consensus on how we hope to resolve the issues arising from the recent introduction of five.localsitemanager and the deprecation of getToolByName.

We believe that these recent changes have introduced implicit magic into a standard Zope3 api to fit Zope2 acquisition. There should be an explicit separate api if we want acquisition wrapped context-aware utilities. As an example of a symptom caused by the implicit implementation, KSS (which was developed as a pure zope 3 component) breaks when used with Plone, even though it is a perfectly valid z3 component. Once we return to using getToolByName for tool lookup, the KSS/Plone3 issue disappears, because the magic wrapping of things stops. This KSS/Plone3 issue arises because the five.lsm acquisition breaks down when you add in non five.lsm component registries. If you need Zope2 acquisition, you should use an accessor api to get things wrapped.


In addition, getToolByName is the most fundamental and widely used api in all of CMF, and we're going to be issuing hundreds of deprecating warnings for every single cmf application extant.

As a solution, we propose

* The five.localsitemanager code should *NOT* be dealing with acquisition, it should be restricted to setting up a bases chain for persistent components that does parent lookup.

* getToolByName deprecation should be reverted. Its internal mechanisms should be kept the same as in the current CMF 2.1 release, using getUtility, *AND* it should be the one doing acquisition wrapping.

So instead of doing implicit magic in the getUtility call stack, let's be explicit, while still allowing the flexibility that registered components provide. Which in turn results in an untouched zope3 getUtility execution path for looking up utilities.

getToolByName should return acquisition wrapped utilities via name mapping, and become un-deprecated. Context for wrapping would be the context passed as an argument to getToolByName, as it always has been. It would issue deprecation warnings when it has to lookup a tool via aq_get instead of getUtility. The mechanism for registering tool names would raise an error when anyone tries to register a component which does not support Acquisition.

The getToolByInterfaceName method would no longer be necessary as getToolByName can be called from restricted code. However if needed it could remain and use the result of getSite() as the context for wrapping the tool resulting from the utility lookup.

We don't mean to belittle the hard work that anyone has put into this so far, and we hope this is received in the spirit that it is intended. We are willing to implement this if we can reach some consensus that this is the right thing to do.

-kapil
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