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[buckminster-dev] Re: Components that come into existence during a build
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Done some more thinking. In essence the previous example can be modified to read something
like this:
<dependencies>
<dependency name="B"/>
<dependency name="G">
<prerequisites>
<external name="B" action="create.G"/>
</prerequisites>
</dependency>
</dependencies>
Buckminster would read this as "Don't make an attempt to resolve "G" until you have executed
the action "B.create.G". An additional interpretation could be that "G" is the product of
its prerequisites.
I think this is a simpler and more flexible approach then using subcomponents. It solves the
same problem with an already known syntax. More then one prerequisite may exist and a
prerequisite may be local.
- thomas
We need some way of expressing Action 'x' in component 'A' needs the
result of action 'y' in the generated component 'G'. The CSPEC format
can be discussed. Perhaps it's an extension to the Action rather then a
subcomponent? How would you do the following?
In the CSPEC for A
<dependencies>
<dependency name="G" subcomponentOf="B"/>
</dependencies>
<actions>
<public name="x" .../>
<prerequisites>
<external component="G" attribute="y"/>
</prerequisites>
...
</public>
</actions>
In the B CSPEC
<subcomponents>
<subcomponent name="G" action="create.G"/>
</subcomponent>
Expected flow:
1. Something triggers action A.x.
2. Buckminster wants to resolve the prerequisite G.y.
3. It asks for the CSPEC of G via the dependency.
4. Finds the subcomponentOf="B" declaration.
5. B is brought in and the subcomponent entry for G is obtained.
6. The action 'create.G' is executed.
7. Once completed, the G CSPEC is obtained and returned all the way up.
8. G.y can now be resolved (which in turn might trigger actions in G)
Another side-effect that Henrik and I discussed is how to deal with
dependencies in the generated component. How do we resolve them? Do we
allow them at all? Do we allow that they go beyond the dependencies
expressed by the generating component? If so, in what scope do we
materialize them?
Muddy waters, yes. Let's pour some chlorine into it :)
- thomas
