Distribution/Simple/Compiler.hs

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Compiler
    -- Copyright   :  Isaac Jones 2003-2004
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This should be a much more sophisticated abstraction than it is. Currently
    -- it's just a bit of data about the compiler, like it's flavour and name and
    -- version. The reason it's just data is because currently it has to be in
    -- 'Read' and 'Show' so it can be saved along with the 'LocalBuildInfo'. The
    -- only interesting bit of info it contains is a mapping between language
    -- extensions and compiler command line flags. This module also defines a
    -- 'PackageDB' type which is used to refer to package databases. Most compilers
    -- only know about a single global package collection but GHC has a global and
    -- per-user one and it lets you create arbitrary other package databases. We do
    -- not yet fully support this latter feature.

    {- All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are
    met:

        * Redistributions of source code must retain the above copyright
          notice, this list of conditions and the following disclaimer.

        * Redistributions in binary form must reproduce the above
          copyright notice, this list of conditions and the following
          disclaimer in the documentation and/or other materials provided
          with the distribution.

        * Neither the name of Isaac Jones nor the names of other
          contributors may be used to endorse or promote products derived
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    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -}

    module Distribution.Simple.Compiler (
            -- * Haskell implementations
            module Distribution.Compiler,
            Compiler(..),
            showCompilerId, compilerFlavor, compilerVersion,

            -- * Support for package databases
            PackageDB(..),
            PackageDBStack,
            registrationPackageDB,
            absolutePackageDBPaths,
            absolutePackageDBPath,

            -- * Support for optimisation levels
            OptimisationLevel(..),
            flagToOptimisationLevel,

            -- * Support for language extensions
            Flag,
            languageToFlags,
            unsupportedLanguages,
            extensionsToFlags,
            unsupportedExtensions
      ) where

    import Distribution.Compiler
    import Distribution.Version (Version(..))
    import Distribution.Text (display)
    import Language.Haskell.Extension (Language(Haskell98), Extension)

    import Control.Monad (liftM)
    import Data.List (nub)
    import Data.Maybe (catMaybes, isNothing)
    import System.Directory (canonicalizePath)

    data Compiler = Compiler {
            compilerId              :: CompilerId,
            compilerLanguages       :: [(Language, Flag)],
            compilerExtensions      :: [(Extension, Flag)]
        }
        deriving (Show, Read)

    showCompilerId :: Compiler -> String
    showCompilerId = display . compilerId

    compilerFlavor ::  Compiler -> CompilerFlavor
    compilerFlavor = (\(CompilerId f _) -> f) . compilerId

    compilerVersion :: Compiler -> Version
    compilerVersion = (\(CompilerId _ v) -> v) . compilerId

    -- ------------------------------------------------------------
    -- * Package databases
    -- ------------------------------------------------------------

    -- |Some compilers have a notion of a database of available packages.
    -- For some there is just one global db of packages, other compilers
    -- support a per-user or an arbitrary db specified at some location in
    -- the file system. This can be used to build isloated environments of
    -- packages, for example to build a collection of related packages
    -- without installing them globally.
    --
    data PackageDB = GlobalPackageDB
                   | UserPackageDB
                   | SpecificPackageDB FilePath
        deriving (Eq, Ord, Show, Read)

    -- | We typically get packages from several databases, and stack them
    -- together. This type lets us be explicit about that stacking. For example
    -- typical stacks include:
    --
    -- > [GlobalPackageDB]
    -- > [GlobalPackageDB, UserPackageDB]
    -- > [GlobalPackageDB, SpecificPackageDB "package.conf.inplace"]
    --
    -- Note that the 'GlobalPackageDB' is invariably at the bottom since it
    -- contains the rts, base and other special compiler-specific packages.
    --
    -- We are not restricted to using just the above combinations. In particular
    -- we can use several custom package dbs and the user package db together.
    --
    -- When it comes to writing, the top most (last) package is used.
    --
    type PackageDBStack = [PackageDB]

    -- | Return the package that we should register into. This is the package db at
    -- the top of the stack.
    --
    registrationPackageDB :: PackageDBStack -> PackageDB
    registrationPackageDB []  = error "internal error: empty package db set"
    registrationPackageDB dbs = last dbs

    -- | Make package paths absolute

    absolutePackageDBPaths :: PackageDBStack -> IO PackageDBStack
    absolutePackageDBPaths = mapM absolutePackageDBPath

    absolutePackageDBPath :: PackageDB -> IO PackageDB
    absolutePackageDBPath GlobalPackageDB        = return GlobalPackageDB
    absolutePackageDBPath UserPackageDB          = return UserPackageDB
    absolutePackageDBPath (SpecificPackageDB db) =
      SpecificPackageDB `liftM` canonicalizePath db

    -- ------------------------------------------------------------
    -- * Optimisation levels
    -- ------------------------------------------------------------

    -- | Some compilers support optimising. Some have different levels.
    -- For compliers that do not the level is just capped to the level
    -- they do support.
    --
    data OptimisationLevel = NoOptimisation
                           | NormalOptimisation
                           | MaximumOptimisation
        deriving (Eq, Show, Read, Enum, Bounded)

    flagToOptimisationLevel :: Maybe String -> OptimisationLevel
    flagToOptimisationLevel Nothing  = NormalOptimisation
    flagToOptimisationLevel (Just s) = case reads s of
      [(i, "")]
        | i >= fromEnum (minBound :: OptimisationLevel)
       && i <= fromEnum (maxBound :: OptimisationLevel)
                    -> toEnum i
        | otherwise -> error $ "Bad optimisation level: " ++ show i
                            ++ ". Valid values are 0..2"
      _             -> error $ "Can't parse optimisation level " ++ s

    -- ------------------------------------------------------------
    -- * Languages and Extensions
    -- ------------------------------------------------------------

    unsupportedLanguages :: Compiler -> [Language] -> [Language]
    unsupportedLanguages comp langs =
      [ lang | lang <- langs
             , isNothing (languageToFlag comp lang) ]

    languageToFlags :: Compiler -> Maybe Language -> [Flag]
    languageToFlags comp = filter (not . null)
                         . catMaybes . map (languageToFlag comp)
                         . maybe [Haskell98] (\x->[x])

    languageToFlag :: Compiler -> Language -> Maybe Flag
    languageToFlag comp ext = lookup ext (compilerLanguages comp)

    -- |For the given compiler, return the extensions it does not support.
    unsupportedExtensions :: Compiler -> [Extension] -> [Extension]
    unsupportedExtensions comp exts =
      [ ext | ext <- exts
            , isNothing (extensionToFlag comp ext) ]

    type Flag = String

    -- |For the given compiler, return the flags for the supported extensions.
    extensionsToFlags :: Compiler -> [Extension] -> [Flag]
    extensionsToFlags comp = nub . filter (not . null)
                           . catMaybes . map (extensionToFlag comp)

    extensionToFlag :: Compiler -> Extension -> Maybe Flag
    extensionToFlag comp ext = lookup ext (compilerExtensions comp)