On Thu, May 6, 2010 at 7:06 AM, Andreas Raab <andreas.raab at gmx.de> wrote:

> Hi -
>
> I've been trying to wet my feet with Metacello a little by writing a
> ConfigurationOfWebClient and in the process I've come across various things
> that I don't understand or don't know how to express. The configuration
> itself can be found here:
>
>        http://www.squeaksource.com/MetacelloRepository
>
> Here are the questions I'm having:
>
> 1) #includes: vs. #requires:
> What is the difference between #includes: and #requires:? They sound
> entirely interchangeable, in particular after reading the tutorial which
> states:
>
>        "When you use the #includes: directive, you are not only specifying
> that the listed packages should be loaded when the parent package is loaded,
> but that the #included: packages should be loaded _before_ any packages that
> require the parent package."
>
> I would expect that precise behavior for required packages, i.e., if Foo
> requires: Bar then Bar is loaded before Foo if some other package requires:
> Foo. What am I missing?
>
> 2) Why is HelpSystem not loaded?
> In my configuration, baseline specifies that HelpSystem is required for
> WebClient-Help:
>
>                "Documentation doesn't require Core/Tests, but HelpSystem"
>                spec package: 'WebClient-Help' with:[spec requires:
> 'HelpSystem'].
>
>                spec project: 'HelpSystem' with:[
>                        spec
>                                className: 'ConfigurationOfHelpSystem';
>                                repository: '
> http://www.squeaksource.com/MetacelloRepository'
>                ].
>
> However, when executed, Metacello goes through the motions but doesn't
> actually *load* any version of HelpSystem (I can see it 'fetch' the packages
> but not load them). It even calls the postLoadDoIt on it (which fails since
> nothing was loaded). What am I doing wrong?
>
>
Hi Andreas, I am not sure, but did you try setting also the file:

     "Documentation doesn't require Core/Tests, but HelpSystem"
               spec package: 'WebClient-Help' with:[spec requires:
'HelpSystem'].

               spec project: 'HelpSystem' with:[
                       spec
                               className: 'ConfigurationOfHelpSystem';
                               repository: '
http://www.squeaksource.com/MetacelloRepository';
                               file: 'ConfigurationOfHelpSystem';
               ].


I saw in your final version you added a version: '1.1' and I saw you put a
comment saying that's a Metacello bug. It's weird since version: shouldn't
be necessary there.

You should put it in the version.

spec
            package: 'WebClient-Core' with: 'WebClient-Core-ar.16';
            package: 'WebClient-Tests' with: 'WebClient-Tests-ar.7';
            package: 'WebClient-Help' with: 'WebClient-Help-ar.5';
            package: 'WebClient-HTTP' with: 'WebClient-HTTP-ar.1'.
spec
            project: 'HelpSystem' with: '1.1'.



> 3) When exactly is HelpSystem loaded?
>
> What I'm wondering about in the above is that HelpSystem should only be
> loaded if WebClient-Help is being loaded. Is this implicitly part of
> specifying a 'project' instead of a 'package'? Or is there some other way of
> specifying that?
>
> I guess really the question here is what entities get loaded implicitly
> simply by declaring them (packages for sure, any others?) and what entities
> need to be 'required' in order to be loaded?
>
>
If you don't define groups in your configuration, it will load by default
all the declarations: packages and projects.

If you want to change that, you can add to your conf something like this:

spec
            group: 'default' with: #('Core' );
            group: 'Core' with: #( 'WebClient-Core' "...");
            group: 'Tests' with: #( 'WebClient-Tests' "...");
            "....."
            yourself.

With that, when you call "load" it will only load Core. Then,  you can do
this:

(ConfigurationOfWebClient project version: '1.0') load: 'Test'
or
(ConfigurationOfWebClient project version: '1.0') load: 'WebClient-Core'
or
(ConfigurationOfWebClient project version: '1.0') load: {'WebClient-Core'
'WebClient-HTTP'}.

The parameter to load: can be a package name, a group or an an array of
them.



> 4) How does one define dependencies that differ based on platform?
>
> In WebClient, the WebClient-HTTP package requires WebClient-Core and -only
> for: #pharo- also WebClient-Pharo. How does one express that there's an
> additional dependency for WebClient-HTTP that only exists for: #pharo? The
> config currently specifies:
>
>        spec for: #common do:[
>                " ... "
>                spec package: 'WebClient-HTTP' with:[spec requires:
> 'WebClient-Core'].
>                " ... "
>        ].
>
>        spec for: #pharo do:[
>                "Just the fact it exists; no requirements here"
>                spec package: 'WebClient-Pharo'.
>        ].
>
>

The only thing that comes to my mind now is to do:


  spec for: #common do:[
               " ... "
               spec package: 'WebClient-HTTP' with:[spec requires:
'WebClient-Core'].
               " ... "
       ].

       spec for: #pharo do:[
               spec package: 'WebClient-HTTP' with:[spec requires: {
'WebClient-Core' 'WebClient-Pharo'} ].

].





> Which means that WebClient-Pharo will be loaded on Pharo by default but
> it's missing the fact that WebClient-Pharo is in fact a requirement for
> WebClient-HTTP (but only on that platform). How is that best expressed?
>
> 5) Bootstrapping Metacello?
>
> I found that most of the ConfigurationsOfXXX include some code to
> 'bootstrap' Metacello in some form. There appear to be variants on the code;
> is there a "canonical bootstrap method" that should be used?
>
> 6) A standard Configuration template?
>
> The Metacello tutorial is very useful as far as the configuration goes but
> it falls short of getting into the details of what it means to provide a
> 'working' configuration. Testing the configuration isn't covered (is there a
> way to get back to a 'clean' state?); bootstrapping isn't covered; the
> meaning of #isMetacelloConfig, #metacelloVesion:loads:,
> #lastMetacelloVersionLoad and several other -seemingly random- methods that
> can be found on most -but not all- of the configurations. There is no
> indication on what these do, if they're required, recommended, or optional.
> Is there some 'standard' Configuration template that people can use to avoid
> guessing about which parts of the boilerplate to copy from some other
> configuration?
>
> That's it for now. Thanks for any insights on any of these issues.
>
> Cheers,
>  - Andreas
>
>
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