Cabal- A framework for packaging Haskell software

CopyrightIsaac Jones 2003-2004
Safe HaskellSafe




Defines a package identifier along with a parser and pretty printer for it. PackageIdentifiers consist of a name and an exact version. It also defines a Dependency data type. A dependency is a package name and a version range, like "foo >= 1.2 && < 2".


Package ids

type PackageId = PackageIdentifier Source

Type alias so we can use the shorter name PackageId.

Installed package identifiers

newtype InstalledPackageId Source

An InstalledPackageId uniquely identifies an instance of an installed package. There can be at most one package with a given InstalledPackageId in a package database, or overlay of databases.

Package keys (used for linker symbols and library name)

data PackageKey Source

A PackageKey is the notion of "package ID" which is visible to the compiler. Why is this not a PackageId? The PackageId is a user-visible concept written explicity in Cabal files; on the other hand, a PackageKey may contain, for example, information about the transitive dependency tree of a package. Why is this not an InstalledPackageId? A PackageKey affects the ABI because it is used for linker symbols; however, an InstalledPackageId can be used to distinguish two ABI-compatible versions of a library.

The key is defined to be a 128-bit MD5 hash, separated into two 64-bit components (the most significant component coming first) which are individually base-62 encoded (A-Z, a-z, 0-9).

     key         ::= hash64 hash64
     hash64      ::= [A-Za-z0-9]{11}

The string that is hashed is specified as raw_key:

     raw_key     ::= package_id "n"
     package_id  ::= package_name "-" package_version
     holes_nl    ::= ""
                   | hole_inst "n" holes_nl
     hole_inst   ::= modulename " " key ":" modulename
     depends_nl  ::= ""
                   | depend "n" depends_nl
     depend      ::= key

The holes list MUST be sorted by the first modulename; the depends list MUST be sorted by the key. holes describes the backing implementations of all holes in the package; depends describes all of the build-depends of a package. A package key MAY be used in holes even if it is not mentioned in depends: depends contains STRICTLY packages which are textually mentioned in the package description.

The trailing newline is MANDATORY.

There is also a variant of package key which is prefixed by a informational string. This key MUST NOT be used in the computation of the hash proper, but it is useful for human-readable consumption.

     infokey     ::= infostring "_" key
     infostring  ::= [A-Za-z0-9-]+

For example, Cabal provides a key with the first five characters of the package name for linker symbols.


PackageKey !String !Word64 !Word64

Modern package key which is a hash of the PackageId and the transitive dependency key. Manually inline it here so we can get the instances we need. Also contains a short informative string

OldPackageKey !PackageId

Old-style package key which is just a PackageId. Required because old versions of GHC assume that the sourcePackageId recorded for an installed package coincides with the package key it was compiled with.

mkPackageKey :: Bool -> PackageId -> [PackageKey] -> [(ModuleName, (PackageKey, ModuleName))] -> PackageKey Source

Generates a PackageKey from a PackageId, sorted package keys of the immediate dependencies.

Package source dependencies

Package classes

class Package pkg where Source

Class of things that have a PackageIdentifier

Types in this class are all notions of a package. This allows us to have different types for the different phases that packages go though, from simple name/id, package description, configured or installed packages.

Not all kinds of packages can be uniquely identified by a PackageIdentifier. In particular, installed packages cannot, there may be many installed instances of the same source package.

class Package pkg => PackageFixedDeps pkg where Source

Subclass of packages that have specific versioned dependencies.

So for example a not-yet-configured package has dependencies on version ranges, not specific versions. A configured or an already installed package depends on exact versions. Some operations or data structures (like dependency graphs) only make sense on this subclass of package types.


depends :: pkg -> [PackageIdentifier] Source

class Package pkg => PackageInstalled pkg where Source

Class of installed packages.

The primary data type which is an instance of this package is InstalledPackageInfo, but when we are doing install plans in Cabal install we may have other, installed package-like things which contain more metadata. Installed packages have exact dependencies installedDepends.