[Zope3-dev] Ranking adapters (2nd try)

[Jim Fulton]

Sorry, lots of typos in the previous attempt.  Here's an
updated version:

I'm noodling some adapter lookup issues as part of adaptergeddon.
Here's a hypothetical situation:

We have 5 interfaces:

   class F0(interface): pass
   class F1(F0): pass

   class B0(interface): pass
   class B1(B0): pass
   class B2(B1): pass

We have two locations/sites, L1 and L2, such that L2 is contained in
(is a subsite of) L1.

We have the following adapter definitions in L1:

   A110 from F1 to B0
   A111 from F1 to B1
   A112 from F1 to B2

We have the following adapter definitions in L2:

   A200 from F0 to B0
   A212 from F1 to B2

(It helps to make a picture, but I can't attach one.)

Now, suppose that we need an adapter from F1 to B0.
We can use any of the adapters above.  How would we rank
the above adapters?  I suggest:

   A212
   A110
   A111
   A112
   A200

The rational?

The most important factor is the interface being adapted.
The second most important factor is location.
The third most important factor is the interface being adapted to.

If we want a B, we don't really care much whether we get a B, a B1,
or a B2.  It's fairly important to be able to override things locally,
but it's not as important as getting an adapter tailored to the object.

Thoughts? Comments?

Jim

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