Distribution/Types/MungedPackageName.hs

    {-# LANGUAGE GeneralizedNewtypeDeriving #-}
    {-# LANGUAGE DeriveDataTypeable #-}
    {-# LANGUAGE DeriveGeneric #-}
    module Distribution.Types.MungedPackageName
      ( MungedPackageName, unMungedPackageName, mkMungedPackageName
      , computeCompatPackageName
      , decodeCompatPackageName
      ) where

    import Prelude ()
    import Distribution.Compat.Prelude
    import Distribution.Utils.ShortText

    import qualified Text.PrettyPrint as Disp
    import qualified Distribution.Compat.ReadP as Parse
    import Distribution.ParseUtils
    import Distribution.Text
    import Distribution.Types.PackageName
    import Distribution.Types.UnqualComponentName

    -- | A combination of a package and component name used in various legacy
    -- interfaces, chiefly bundled with a version as 'MungedPackageId'. It's generally
    -- better to use a 'UnitId' to opaquely refer to some compilation/packing unit,
    -- but that doesn't always work, e.g. where a "name" is needed, in which case
    -- this can be used as a fallback.
    --
    -- Use 'mkMungedPackageName' and 'unMungedPackageName' to convert from/to a 'String'.
    --
    -- @since 2.0.0.2
    newtype MungedPackageName = MungedPackageName ShortText
        deriving (Generic, Read, Show, Eq, Ord, Typeable, Data)

    -- | Convert 'MungedPackageName' to 'String'
    unMungedPackageName :: MungedPackageName -> String
    unMungedPackageName (MungedPackageName s) = fromShortText s

    -- | Construct a 'MungedPackageName' from a 'String'
    --
    -- 'mkMungedPackageName' is the inverse to 'unMungedPackageName'
    --
    -- Note: No validations are performed to ensure that the resulting
    -- 'MungedPackageName' is valid
    --
    -- @since 2.0.0.2
    mkMungedPackageName :: String -> MungedPackageName
    mkMungedPackageName = MungedPackageName . toShortText

    -- | 'mkMungedPackageName'
    --
    -- @since 2.0.0.2
    instance IsString MungedPackageName where
      fromString = mkMungedPackageName

    instance Binary MungedPackageName

    instance Text MungedPackageName where
      disp = Disp.text . unMungedPackageName
      parse = mkMungedPackageName <$> parsePackageName

    instance NFData MungedPackageName where
        rnf (MungedPackageName pkg) = rnf pkg

    -- | Computes the package name for a library.  If this is the public
    -- library, it will just be the original package name; otherwise,
    -- it will be a munged package name recording the original package
    -- name as well as the name of the internal library.
    --
    -- A lot of tooling in the Haskell ecosystem assumes that if something
    -- is installed to the package database with the package name 'foo',
    -- then it actually is an entry for the (only public) library in package
    -- 'foo'.  With internal packages, this is not necessarily true:
    -- a public library as well as arbitrarily many internal libraries may
    -- come from the same package.  To prevent tools from getting confused
    -- in this case, the package name of these internal libraries is munged
    -- so that they do not conflict the public library proper.  A particular
    -- case where this matters is ghc-pkg: if we don't munge the package
    -- name, the inplace registration will OVERRIDE a different internal
    -- library.
    --
    -- We munge into a reserved namespace, "z-", and encode both the
    -- component name and the package name of an internal library using the
    -- following format:
    --
    --      compat-pkg-name ::= "z-" package-name "-z-" library-name
    --
    -- where package-name and library-name have "-" ( "z" + ) "-"
    -- segments encoded by adding an extra "z".
    --
    -- When we have the public library, the compat-pkg-name is just the
    -- package-name, no surprises there!
    --
    computeCompatPackageName :: PackageName -> Maybe UnqualComponentName -> MungedPackageName
    -- First handle the cases where we can just use the original 'PackageName'.
    -- This is for the PRIMARY library, and it is non-Backpack, or the
    -- indefinite package for us.
    computeCompatPackageName pkg_name Nothing
        = mkMungedPackageName $ unPackageName pkg_name
    computeCompatPackageName pkg_name (Just uqn)
        = mkMungedPackageName $
             "z-" ++ zdashcode (unPackageName pkg_name) ++
            "-z-" ++ zdashcode (unUnqualComponentName uqn)

    decodeCompatPackageName :: MungedPackageName -> (PackageName, Maybe UnqualComponentName)
    decodeCompatPackageName m =
        case unMungedPackageName m of
            'z':'-':rest | [([pn, cn], "")] <- Parse.readP_to_S parseZDashCode rest
                -> (mkPackageName pn, Just (mkUnqualComponentName cn))
            s   -> (mkPackageName s, Nothing)

    zdashcode :: String -> String
    zdashcode s = go s (Nothing :: Maybe Int) []
        where go [] _ r = reverse r
              go ('-':z) (Just n) r | n > 0 = go z (Just 0) ('-':'z':r)
              go ('-':z) _        r = go z (Just 0) ('-':r)
              go ('z':z) (Just n) r = go z (Just (n+1)) ('z':r)
              go (c:z)   _        r = go z Nothing (c:r)

    parseZDashCode :: Parse.ReadP r [String]
    parseZDashCode = do
        ns <- Parse.sepBy1 (Parse.many1 (Parse.satisfy (/= '-'))) (Parse.char '-')
        Parse.eof
        return (go ns)
      where
        go ns = case break (=="z") ns of
                    (_, []) -> [paste ns]
                    (as, "z":bs) -> paste as : go bs
                    _ -> error "parseZDashCode: go"
        unZ :: String -> String
        unZ "" = error "parseZDashCode: unZ"
        unZ r@('z':zs) | all (=='z') zs = zs
                       | otherwise      = r
        unZ r = r
        paste :: [String] -> String
        paste = intercalate "-" . map unZ