goran.hultgren at bluefish.se wrote:
> Julian Fitzell <julian at beta4.com> wrote:
> 
>>goran.hultgren at bluefish.se wrote:
>>
>>>Julian Fitzell <julian at beta4.com> wrote:
>>>[SNIP]
>>>
>>>
>>>>I didn't say SqueakMap depended on SARInstaller.  I meant that packages 
>>>>that are packaged as SARs depend on SARInstaller.  So when you try to 
>>>>install a SAR package and don't have SARInstaller, it will get installed 
>>>>first since it is a dependency.
>>>
>>>
>>>Duh. Ok, sorry - didn't read careful enough. Yes, this would be neat.
>>>But... hmmm. Interesting. It wouldn't work at all with the current
>>>architecture - nor the one I am aiming for in 1.1. Hmmmm.
>>
>>I'm curious why it doesn't work with what you're planning.  Isn't it 
>>just a simple matter of giving the package a dependency on the 
>>installer?  Presumably all the dependencies are installed prior to the 
>>package itsself?
>>
>>I'm guessing I'm missing something obvious.
> 
> 
> Well, there are two issues at play here:
> 
> 1. The service architecture for finding the "actions" that you can do
> with a package. Today each subclass of SMInstaller is queried if it
> would like to handle package x and the first one that says yes gets to
> supply "download" and/or "install". So if you don't have the installer
> already installed - how does it raise its hand and say "Yes, I can
> handle this package!". The future architecture that I have started
> fiddling with collects services from registered "package handler
> objects" instead - the services can be anything and there may be
> services from multiple handlers. Anyway, the problem is still the same.

Well, my initial reaction is to say that if you install the 
prerequisites *before* asking for an installer for the specified 
package, then the installer would be there by the time you asked the 
question.  That said, however...

> 2. When thinking more this is actually not a normal dependency. In the
> planned SM 1.1+ people will register "package configurations" with the
> dependencies for *using* package x. Not the dependencies for
> *installing* it. I think these two things are different - for example -
> the installer can easily be uninstalled after it has done its work - a
> "normal" dependency can't be.

You're right, it does seem a little different.  It's sort of an implicit 
dependency.  I wasn't thinking you'd want to list it as a dependency 
manually, I was thinking that the system would automatically add it as a 
dependency only while calculating what to install.

It is also made more complex by the ability to have more than one 
installer handle the package.

Ok, well.... how about it you ask the system if there is an installer 
that can handle the package.  If so, great.  If not, you add an implicit 
dependency to the default installer defined for the package type (how we 
determine this is of course the key issue), install all your dependents, 
and then try again.

As for being able to uninstall the installer, there's nothing preventing 
you from uninstalling any dependency at a later point so obviously you 
can physically remove it.  And since the installer wouldn't actually be 
listed in the configuration (since it's implicit) it doesn't suggest to 
the user that they shouldn't be able to remove it.

> So, what do we do? Well, after thinking about 20 seconds I am not sure I
> would like to use "normal" dependencies for this. And it does feel like
> overkill to introduce some other dependency structure just to handle
> installation. I think perhaps we should be a bit more strict when it
> comes to "Package type" - perhaps making it mandatory. And given this we
> could perhaps map to at least a default installer package. I am not
> sure..
> 
> I need to get a new revision of SM out - if you have any bright ideas
> regarding the above I am listening.
> 
> regards, Göran
> 
> 

That's about the best I can come up with at the moment.  The only other 
solution would be to remove the ability to have multiple installers 
handle the package.  This does seem appropriate to have though in an 
environment like Squeak where you might have written your own version of 
an installer that handle DVS packages, for example.

Julian


-- 
julian at beta4.com
Beta4 Productions (http://www.beta4.com)