[Zope-dev] improving the utility and adapter lookup APIs

[Hanno Schlichting]

On Wed, Nov 25, 2009 at 9:52 PM, Tres Seaver <tseaver at palladion.com> wrote:
> Hmm, I may be missing something here, but if Foo implements IFoo, then
> the getAdapter lookup for it will short circuit, leading you into
> infinite recursion.  Except that it doesn't:

[snip example]

> which strikes me as wildly disjoint:  the IFoo behavior is "expected"
> (short-circuit the lookup if the object already provides the interface),
> while the getAdapter behavior is a puzzlement.

This has been mentioned numerous times as one of those odd and
unexpected differences between the IFoo vs. get/queryAdapter semantic.
IIRC the only use-case I ever heard of for the getAdapter semantic,
was the possibility to override the behavior promised by the interface
with a different adapter without touching the class that implements
the interface directly.

I think changing this falls into the category of: Small backwards
incompatibly that seem worthwhile to make the behavior consistent and
expected.

Hanno