On Mon, Oct 11, 2010 at 11:18 PM, Luke Kanies <[email protected]> wrote:
> On Oct 9, 2010, at 11:10 AM, Nigel Kersten wrote:
> > Just so I'm perfectly clear on how this will work with inheritance...
> > What will happen here with File["foo"] under the proposed model?
> >
> >
> > class nkotb {
> > File { owner => "root",}
> > }
> >
> > class nsync inherits nkotb {
> > file { "foo":
> > ...
> > }
> > }
>
> I actually don't know how the lexical scoping will affect scoping and
> inheritance. I assume that File["foo"] would acquire owner => root; Paul?
>
Nick and I were debating this question on Friday. The current behavior in
2.6 is that things defined in a base class (whether variables or resource
defaults) are inherited by the derived class, and that they take precedence
over dynamic scope. My preference would be to keep this behavior, so that
things defined in a base class are inherited by the derived class, and take
precedence over lexical scope. So yes, in my vision of how Nigel's example
would work, File["foo"] would acquire owner => root, just as it does in 2.6.
To give a more complex example:
class A {
class B {
class C { }
class D inherits C { }
class E inherits D { }
}
}
My vision of things is that for resources defined inside class E, variable
references and resource defaults would be looked up in this order:
- class E
- class D (inheritance: D is the base of E)
- class C (inheritance: C is the base of D, which is the base of E)
- class B (lexical scoping: B contains E)
- class A (lexical scoping: A contains B, which contains E)
- toplevel (lexical scoping: A is a toplevel construct, and A contains B,
which contains E)
Here's a tricky question: how should Puppet behave when there is a
combination of inheritance and lexical scoping? For example:
class A {
class B { }
}
class C inherits E {
class D inherits B { }
}
class E { }
So, A contains B, which is the base of D. Should variables and resource
defaults in A apply to D? Similarly, E is the base of C, which contains D.
Should variables and resource defaults in E apply to D? If the answer to
either of these questions is yes, what is the order of precedence? My
current answer is "no", just because I'm trying to keep things simple. But
I'm open to change my mind if someone can make a case for a different
behavior :)
Paul
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