Minor type class cleanup #2487
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Minor type class cleanup #2487
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The fundamental difference between Cabal and cabal-install is that the former deals with installed libraries, and -- in principle -- knows about _library_ dependencies only, whereas the latters deals with setup, executable, test-suite and benchmark dependencies in addition to library dependencies. Currently we classify all of these simply as 'dependencies' but that will change shortly. In this commit we take a first step towards this by moving the PackageFixedDeps class, which deals with dependencies of packages rather than installed libraries, from Cabal to cabal-install. The commit is pretty simple; we just move the type class and update import statements where necessary.
Introduce a new superclass HasInstalledPackageId:
class Package pkg => HasInstalledPackageId pkg where
installedPackageId :: pkg -> InstalledPackageId
class HasInstalledPackageId pkg => PackageInstalled pkg where
installedDepends :: pkg -> [InstalledPackageId]
Most functions that deal with the package index now just require
HasInstalledPackageId; only the functions that actually require the
dependencies still rely on PackageInstalled.
The point is that a ConfiguredPackage/ReadyPackage/PlanPackage can reasonably
be made an instance of HasInstalledPackageId, but not of PackageInstalled; that
will be the topic of the next, much larger, pull request.
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This is ok with me. |
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This seems to be noncontroversial, so merging. |
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This pull request is the first of a set of pull requests working towards an implementation of setup dependencies.
This PR moves
installedPackageIdout ofPackageInstalledinto a new superclassHasInstalledPackageId, and moves thePackageFixedDepsclass fromCabaltocabal-install./cc @dcoutts @kosmikus