[Zope] aq_inner and acquisition by containment only

[Stefan Bund]

Hi list,

while solving a somewhat intricate acquisition problem, I came
discovered, that the statement, that aq_inner will return an object
wrapped by containment only seems to be incorrect. Here is the
simplified scenario to show this:

Let a and c be attributes of x, let b be an attribute of a. Then
x.a.c.a.b is the acquisition tree (as shown in Zope 2.7.0 using a little
tool akin showaq)

O-[b]
|
O-O-[a]
| |
| [x]
|
O-O-[c]
| |
| [x]
|
O-[a]
|
[x]

(self goes to the right, parent down). The important thing is, that
aq_inner of this is the same tree. I would have expexted to get the
reduced tree

O-[b]
|
O-[a]
|
[x]

but looking at the first tree, it is obvious, why this is not the
case. The Documentation says, that ( X o Y ) o ( Y o Z ) is simplified
to X o ( Y o Z ). While working out the expression, I could find, that
this simplification will close to the end simplify the b o ( a o x )
subtree away, since the next expression starts with ( a o x ).

This leaves me a little bit uneasy: when searching x.a.c.a.b.aq_inner,
c will be searched even though it is *not* in the containment path of
b !

I would very much like a comment on this ... Is this known behavior?
Should I have expected this?

Stefan.

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