|Copyright||(c) The University of Glasgow 2009, Duncan Coutts 2014|
This module provides the view of GHC's database of registered packages that is shared between GHC the compiler/library, and the ghc-pkg program. It defines the database format that is shared between GHC and ghc-pkg.
The database format, and this library are constructed so that GHC does not have to depend on the Cabal library. The ghc-pkg program acts as the gateway between the external package format (which is defined by Cabal) and the internal package format which is specialised just for GHC.
GHC the compiler only needs some of the information which is kept about registerd packages, such as module names, various paths etc. On the other hand ghc-pkg has to keep all the information from Cabal packages and be able to regurgitate it for users and other tools.
The first trick is that we duplicate some of the information in the package database. We essentially keep two versions of the datbase in one file, one version used only by ghc-pkg which keeps the full information (using the serialised form of the
InstalledPackageInfo type defined by the Cabal library); and a second version written by ghc-pkg and read by GHC which has just the subset of information that GHC needs.
The second trick is that this module only defines in detail the format of the second version -- the bit GHC uses -- and the part managed by ghc-pkg is kept in the file but here we treat it as an opaque blob of data. That way this library avoids depending on Cabal.
This is a subset of Cabal's
InstalledPackageInfo, with just the bits that GHC is interested in.
|(Eq instpkgid, Eq srcpkgid, Eq srcpkgname, Eq pkgkey, Eq modulename) => Eq (InstalledPackageInfo instpkgid srcpkgid srcpkgname pkgkey modulename)|
|(Show instpkgid, Show srcpkgid, Show srcpkgname, Show pkgkey, Show modulename) => Show (InstalledPackageInfo instpkgid srcpkgid srcpkgname pkgkey modulename)|
|(BinaryStringRep a, BinaryStringRep b, BinaryStringRep c, BinaryStringRep d, BinaryStringRep e) => Binary (InstalledPackageInfo a b c d e)|
Represents a module name which is exported by a package, stored in the
exposedModules field. A module export may be a reexport (in which case
exposedReexport is filled in with the original source of the module), and may be a signature (in which case 'exposedSignature is filled in with what the signature was compiled against). Thus:
ExposedModule n Nothing Nothingrepresents an exposed module
nwhich was defined in this package.
ExposedModule n (Just o) Nothingrepresents a reexported module
nwhich was originally defined in
ExposedModule n Nothing (Just s)represents an exposed signature
nwhich was compiled against the implementation
ExposedModule n (Just o) (Just s)represents a reexported signature which was originally defined in
oand was compiled against the implementation
We use two
Maybe data types instead of an ADT with four branches or four fields because this representation allows us to treat reexports/signatures uniformly.
An original module is a fully-qualified module name (installed package ID plus module name) representing where a module was *originally* defined (i.e., the
exposedReexport field of the original ExposedModule entry should be
Nothing). Invariant: an OriginalModule never points to a reexport.
Read the part of the package DB that GHC is interested in.
Read the part of the package DB that ghc-pkg is interested in
Note that the Binary instance for ghc-pkg's representation of packages is not defined in this package. This is because ghc-pkg uses Cabal types (and Binary instances for these) which this package does not depend on.
Write the whole of the package DB, both parts.
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Licensed under a BSD-style license (see top of the page).