8.10: About Dependency Granularity

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We want to discuss the difference between depending on a package, depending on a project and the different ways to express it. Imagine the following baseline1.1 from Fame.

baseline11: spec
    <version: '1.1-baseline'>

    spec for: #'common' do: [
        spec blessing: #'baseline'.
        spec description: 'Baseline 1.1 first version on SmalltalkHub, copied from baseline
        1.0 on SqueakSource'.
        spec repository: 'http://www.smalltalkhub.com/mc/Moose/Fame/main'.
        spec
            package: 'Fame-Core';
            package: 'Fame-Util';
            package: 'Fame-ImportExport' with: [spec requires: #('Fame-Core' ) ];
            package: 'Fame-SmalltalkBinding' with: [spec requires: #('Fame-Core' ) ];
            package: 'Fame-Example';
            package: 'Phexample' with: [spec repository: 'http://smalltalkhub.com/mc/
         PharoExtras/Phexample/main' ];
            package: 'Fame-Tests-Core' with: [spec requires: #('Fame-Core' 'Fame-
         Example' 'Phexample' ) ].
        spec
            group: 'Core' with: #('Fame-Core' 'Fame-ImportExport' 'Fame-Util' 'Fame-
         SmalltalkBinding' );
            group: 'Tests' with: #('Fame-Tests-Core' ) ].

In this baseline, package: 'Phexample' with: [spec repository: 'http://smalltalkhub. com/mc/PharoExtras/Phexample/main' ]; expresses that there is one package that can be found in the specified repository. However, such an approach is not good because this way you are just downloading a package from a repository and Metacello is not involved. For example, if PhexampleCore has dependencies they will not be loaded.

In the following baseline1.2 we express dependencies between projects as presented above.

baseline12: spec
    <version: '1.2-baseline'>
    
    spec for: #'common' do: [
        spec blessing: #'baseline'.
        spec description: 'Baseline 1.2 to make explicit that Fame depends on HashTable
         and Phexample (now on smalltalkHub and with working configurations'.
        spec repository: 'http://www.smalltalkhub.com/mc/Moose/Fame/main'.

        spec project: 'HashTable' with: [
                spec
                    versionString: #stable;
                    repository: 'http://www.smalltalkhub.com/mc/Moose/HashTable/main' ].

        spec project: 'Phexample' with: [
                spec
                    versionString: #stable;
                    repository: 'http://www.smalltalkhub.com/mc/Phexample/main' ].
        spec
            package: 'Fame-Core' with: [spec requires: 'HashTable'];
            package: 'Fame-Util';
            package: 'Fame-ImportExport' with: [spec requires: #('Fame-Core' ) ];
            package: 'Fame-SmalltalkBinding' with: [spec requires: #('Fame-Core' ) ];
            package: 'Fame-Example';
            package: 'Fame-Tests-Core' with: [spec requires: #('Fame-Core' 'Fame-
         Example') ].
        spec
            group: 'Core' with: #('Fame-Core' 'Fame-ImportExport' 'Fame-Util' 'Fame-
         SmalltalkBinding' );
            group: 'Tests' with: #('Fame-Tests-Core' ) ].

Now when we express dependencies between projects we lose the fact that this is the package Fame-Tests-Core that depends on Phexample and this is a loss of information.

To keep such information we can simply define in our configuration a new project named for example, PhexampleCore and we will be able to express that Fame-Tests-Core is dependent on PhexampleCore as follows.

spec
    project: 'PhexampleCore'
    with: [ spec
            versionString: #stable;
            loads: #('Core');
            repository: 'http://www.smalltalkhub.com/mc/Phexample/main' ].
    ....
    'Fame-Tests-Core' with: [spec requires: #('Fame-Core' 'Fame-Example'
        'PhexampleCore' ) ].