{-# OPTIONS_GHC -cpp #-} ----------------------------------------------------------------------------- -- | -- Module : Distribution.PackageDescription -- Copyright : Isaac Jones 2003-2005 -- -- Maintainer : Isaac Jones -- Stability : alpha -- Portability : portable -- -- Package description and parsing. {- 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 from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -} module Distribution.PackageDescription ( -- * Package descriptions PackageDescription(..), emptyPackageDescription, readPackageDescription, parseDescription, StanzaField(..), LineNo, basicStanzaFields, writePackageDescription, showPackageDescription, sanityCheckPackage, errorOut, setupMessage, Library(..), withLib, hasLibs, libModules, Executable(..), withExe, exeModules, -- * Build information BuildInfo(..), emptyBuildInfo, -- ** Supplementary build information HookedBuildInfo, emptyHookedBuildInfo, readHookedBuildInfo, parseHookedBuildInfo, writeHookedBuildInfo, showHookedBuildInfo, updatePackageDescription, -- * Utilities ParseResult(..), PError, PWarning, showError, hcOptions, autogenModuleName, haddockName, ) where import Control.Monad(liftM, foldM, when) import Data.Char import Data.Maybe(fromMaybe, isNothing, catMaybes) import Data.List (nub,lookup) import Text.PrettyPrint.HughesPJ import System.Directory(doesFileExist) import System.Environment(getProgName) import System.IO(hPutStrLn, stderr) import System.Exit import Distribution.ParseUtils import Distribution.Package(PackageIdentifier(..),showPackageId, parsePackageName) import Distribution.Version(Version(..), VersionRange(..), withinRange, showVersion, parseVersion, showVersionRange, parseVersionRange) import Distribution.License(License(..)) import Distribution.Version(Dependency(..)) import Distribution.Compiler(CompilerFlavor(..)) import Distribution.Simple.Utils(currentDir, die, dieWithLocation, warn) import Language.Haskell.Extension(Extension(..)) import Distribution.Compat.ReadP as ReadP hiding (get) import Distribution.Compat.FilePath(joinFileExt) -- |Fix. Figure out a way to get this from .cabal file cabalVersion :: Version cabalVersion = Version [1,1,4] [] -- | This data type is the internal representation of the file @pkg.cabal@. -- It contains two kinds of information about the package: information -- which is needed for all packages, such as the package name and version, and -- information which is needed for the simple build system only, such as -- the compiler options and library name. -- data PackageDescription = PackageDescription { -- the following are required by all packages: package :: PackageIdentifier, license :: License, licenseFile :: FilePath, copyright :: String, maintainer :: String, author :: String, stability :: String, testedWith :: [(CompilerFlavor,VersionRange)], homepage :: String, pkgUrl :: String, synopsis :: String, -- ^A one-line summary of this package description :: String, -- ^A more verbose description of this package category :: String, buildDepends :: [Dependency], descCabalVersion :: VersionRange, -- ^If this package depends on a specific version of Cabal, give that here. -- components library :: Maybe Library, executables :: [Executable], dataFiles :: [FilePath], extraSrcFiles :: [FilePath], extraTmpFiles :: [FilePath] } deriving (Show, Read, Eq) data Library = Library { exposedModules :: [String], libBuildInfo :: BuildInfo } deriving (Show, Eq, Read) emptyLibrary :: Library emptyLibrary = Library [] emptyBuildInfo emptyPackageDescription :: PackageDescription emptyPackageDescription = PackageDescription {package = PackageIdentifier "" (Version [] []), license = AllRightsReserved, licenseFile = "", descCabalVersion = AnyVersion, copyright = "", maintainer = "", author = "", stability = "", testedWith = [], buildDepends = [], homepage = "", pkgUrl = "", synopsis = "", description = "", category = "", library = Nothing, executables = [], dataFiles = [], extraSrcFiles = [], extraTmpFiles = [] } -- |Get all the module names from the libraries in this package libModules :: PackageDescription -> [String] libModules PackageDescription{library=lib} = maybe [] exposedModules lib ++ maybe [] (otherModules . libBuildInfo) lib -- |Get all the module names from the exes in this package exeModules :: PackageDescription -> [String] exeModules PackageDescription{executables=execs} = concatMap (otherModules . buildInfo) execs -- |does this package have any libraries? hasLibs :: PackageDescription -> Bool hasLibs p = maybe False (buildable . libBuildInfo) (library p) -- |'Maybe' version of 'hasLibs' maybeHasLibs :: PackageDescription -> Maybe Library maybeHasLibs p = library p >>= (\lib -> toMaybe (buildable (libBuildInfo lib)) lib) -- Consider refactoring into executable and library versions. data BuildInfo = BuildInfo { buildable :: Bool, -- ^ component is buildable here ccOptions :: [String], -- ^ options for C compiler ldOptions :: [String], -- ^ options for linker frameworks :: [String], -- ^support frameworks for Mac OS X cSources :: [FilePath], hsSourceDirs :: [FilePath], -- ^ where to look for the haskell module hierarchy otherModules :: [String], -- ^ non-exposed or non-main modules extensions :: [Extension], extraLibs :: [String], -- ^ what libraries to link with when compiling a program that uses your package extraLibDirs :: [String], includeDirs :: [FilePath], -- ^directories to find .h files includes :: [FilePath], -- ^ The .h files to be found in includeDirs installIncludes :: [FilePath], -- ^ .h files to install with the package options :: [(CompilerFlavor,[String])], ghcProfOptions :: [String] } deriving (Show,Read,Eq) emptyBuildInfo :: BuildInfo emptyBuildInfo = BuildInfo { buildable = True, ccOptions = [], ldOptions = [], frameworks = [], cSources = [], hsSourceDirs = [currentDir], otherModules = [], extensions = [], extraLibs = [], extraLibDirs = [], includeDirs = [], includes = [], installIncludes = [], options = [], ghcProfOptions = [] } data Executable = Executable { exeName :: String, modulePath :: FilePath, buildInfo :: BuildInfo } deriving (Show, Read, Eq) emptyExecutable :: Executable emptyExecutable = Executable { exeName = "", modulePath = "", buildInfo = emptyBuildInfo } -- | Perform the action on each buildable 'Executable' in the package -- description. withExe :: PackageDescription -> (Executable -> IO a) -> IO () withExe pkg_descr f = sequence_ [f exe | exe <- executables pkg_descr, buildable (buildInfo exe)] type HookedBuildInfo = (Maybe BuildInfo, [(String, BuildInfo)]) emptyHookedBuildInfo :: HookedBuildInfo emptyHookedBuildInfo = (Nothing, []) -- ------------------------------------------------------------ -- * Utils -- ------------------------------------------------------------ -- |If the package description has a library section, call the given -- function with the library build info as argument. withLib :: PackageDescription -> a -> (Library -> IO a) -> IO a withLib pkg_descr a f = maybe (return a) f (maybeHasLibs pkg_descr) setupMessage :: String -> PackageDescription -> IO () setupMessage msg pkg_descr = putStrLn (msg ++ ' ':showPackageId (package pkg_descr) ++ "...") -- |Update the given package description with the output from the -- pre-hooks. updatePackageDescription :: HookedBuildInfo -> PackageDescription -> PackageDescription updatePackageDescription (mb_lib_bi, exe_bi) p = p{ executables = updateExecutables exe_bi (executables p) , library = updateLibrary mb_lib_bi (library p) } where updateLibrary :: Maybe BuildInfo -> Maybe Library -> Maybe Library updateLibrary (Just bi) (Just lib) = Just (lib{libBuildInfo = unionBuildInfo bi (libBuildInfo lib)}) updateLibrary Nothing mb_lib = mb_lib --the lib only exists in the buildinfo file. FIX: Is this --wrong? If there aren't any exposedModules, then the library --won't build anyway. add to sanity checker? updateLibrary (Just bi) Nothing = Just emptyLibrary{libBuildInfo=bi} updateExecutables :: [(String, BuildInfo)] -- ^[(exeName, new buildinfo)] -> [Executable] -- ^list of executables to update -> [Executable] -- ^list with exeNames updated updateExecutables exe_bi' executables' = foldr updateExecutable executables' exe_bi' updateExecutable :: (String, BuildInfo) -- ^(exeName, new buildinfo) -> [Executable] -- ^list of executables to update -> [Executable] -- ^libst with exeName updated updateExecutable _ [] = [] updateExecutable exe_bi'@(name,bi) (exe:exes) | exeName exe == name = exe{buildInfo = unionBuildInfo bi (buildInfo exe)} : exes | otherwise = exe : updateExecutable exe_bi' exes unionBuildInfo :: BuildInfo -> BuildInfo -> BuildInfo unionBuildInfo b1 b2 = b1{buildable = buildable b1 && buildable b2, ccOptions = combine ccOptions, ldOptions = combine ldOptions, frameworks = combine frameworks, cSources = combine cSources, hsSourceDirs = combine hsSourceDirs, otherModules = combine otherModules, extensions = combine extensions, extraLibs = combine extraLibs, extraLibDirs = combine extraLibDirs, includeDirs = combine includeDirs, includes = combine includes, installIncludes = combine installIncludes, options = combine options } where combine :: (Eq a) => (BuildInfo -> [a]) -> [a] combine f = nub $ f b1 ++ f b2 -- |Select options for a particular Haskell compiler. hcOptions :: CompilerFlavor -> [(CompilerFlavor, [String])] -> [String] hcOptions hc hc_opts = [opt | (hc',opts) <- hc_opts, hc' == hc, opt <- opts] -- |The name of the auto-generated module associated with a package autogenModuleName :: PackageDescription -> String autogenModuleName pkg_descr = "Paths_" ++ map fixchar (pkgName (package pkg_descr)) where fixchar '-' = '_' fixchar c = c haddockName :: PackageDescription -> FilePath haddockName pkg_descr = joinFileExt (pkgName (package pkg_descr)) "haddock" -- ------------------------------------------------------------ -- * Parsing & Pretty printing -- ------------------------------------------------------------ -- the strings for the required fields are necessary here, and so we -- don't repeat ourselves, I name them: reqNameName = "name" reqNameVersion = "version" reqNameCopyright = "copyright" reqNameMaintainer = "maintainer" reqNameSynopsis = "synopsis" basicStanzaFields :: [StanzaField PackageDescription] basicStanzaFields = [ simpleField reqNameName text parsePackageName (pkgName . package) (\name pkg -> pkg{package=(package pkg){pkgName=name}}) , simpleField reqNameVersion (text . showVersion) parseVersion (pkgVersion . package) (\ver pkg -> pkg{package=(package pkg){pkgVersion=ver}}) , simpleField "cabal-version" (text . showVersionRange) parseVersionRange descCabalVersion (\v pkg -> pkg{descCabalVersion=v}) , simpleField "license" (text . show) parseLicenseQ license (\l pkg -> pkg{license=l}) , simpleField "license-file" showFilePath parseFilePathQ licenseFile (\l pkg -> pkg{licenseFile=l}) , simpleField reqNameCopyright showFreeText (munch (const True)) copyright (\val pkg -> pkg{copyright=val}) , simpleField reqNameMaintainer showFreeText (munch (const True)) maintainer (\val pkg -> pkg{maintainer=val}) , commaListField "build-depends" showDependency parseDependency buildDepends (\xs pkg -> pkg{buildDepends=xs}) , simpleField "stability" showFreeText (munch (const True)) stability (\val pkg -> pkg{stability=val}) , simpleField "homepage" showFreeText (munch (const True)) homepage (\val pkg -> pkg{homepage=val}) , simpleField "package-url" showFreeText (munch (const True)) pkgUrl (\val pkg -> pkg{pkgUrl=val}) , simpleField reqNameSynopsis showFreeText (munch (const True)) synopsis (\val pkg -> pkg{synopsis=val}) , simpleField "description" showFreeText (munch (const True)) description (\val pkg -> pkg{description=val}) , simpleField "category" showFreeText (munch (const True)) category (\val pkg -> pkg{category=val}) , simpleField "author" showFreeText (munch (const True)) author (\val pkg -> pkg{author=val}) , listField "tested-with" showTestedWith parseTestedWithQ testedWith (\val pkg -> pkg{testedWith=val}) , listField "data-files" showFilePath parseFilePathQ dataFiles (\val pkg -> pkg{dataFiles=val}) , listField "extra-source-files" showFilePath parseFilePathQ extraSrcFiles (\val pkg -> pkg{extraSrcFiles=val}) , listField "extra-tmp-files" showFilePath parseFilePathQ extraTmpFiles (\val pkg -> pkg{extraTmpFiles=val}) ] executableStanzaFields :: [StanzaField Executable] executableStanzaFields = [ simpleField "executable" showFreeText (munch (const True)) exeName (\xs exe -> exe{exeName=xs}) , simpleField "main-is" showFilePath parseFilePathQ modulePath (\xs exe -> exe{modulePath=xs}) ] binfoFields :: [StanzaField BuildInfo] binfoFields = [ simpleField "buildable" (text . show) parseReadS buildable (\val binfo -> binfo{buildable=val}) , listField "cc-options" showToken parseTokenQ ccOptions (\val binfo -> binfo{ccOptions=val}) , listField "ld-options" showToken parseTokenQ ldOptions (\val binfo -> binfo{ldOptions=val}) , listField "frameworks" showToken parseTokenQ frameworks (\val binfo -> binfo{frameworks=val}) , listField "c-sources" showFilePath parseFilePathQ cSources (\paths binfo -> binfo{cSources=paths}) , listField "extensions" (text . show) parseExtensionQ extensions (\exts binfo -> binfo{extensions=exts}) , listField "extra-libraries" showToken parseTokenQ extraLibs (\xs binfo -> binfo{extraLibs=xs}) , listField "extra-lib-dirs" showFilePath parseFilePathQ extraLibDirs (\xs binfo -> binfo{extraLibDirs=xs}) , listField "includes" showFilePath parseFilePathQ includes (\paths binfo -> binfo{includes=paths}) , listField "install-includes" showFilePath parseFilePathQ includes (\paths binfo -> binfo{installIncludes=paths}) , listField "include-dirs" showFilePath parseFilePathQ includeDirs (\paths binfo -> binfo{includeDirs=paths}) , listField "hs-source-dirs" showFilePath parseFilePathQ hsSourceDirs (\paths binfo -> binfo{hsSourceDirs=paths}) , listField "other-modules" text parseModuleNameQ otherModules (\val binfo -> binfo{otherModules=val}) , listField "ghc-prof-options" text parseTokenQ ghcProfOptions (\val binfo -> binfo{ghcProfOptions=val}) , optsField "ghc-options" GHC options (\path binfo -> binfo{options=path}) , optsField "hugs-options" Hugs options (\path binfo -> binfo{options=path}) , optsField "nhc-options" NHC options (\path binfo -> binfo{options=path}) , optsField "jhc-options" JHC options (\path binfo -> binfo{options=path}) ] -- -------------------------------------------- -- ** Parsing -- | Given a parser and a filename, return the parse of the file, -- after checking if the file exists. readAndParseFile :: (String -> ParseResult a) -> FilePath -> IO a readAndParseFile parser fpath = do exists <- doesFileExist fpath when (not exists) (die $ "Error Parsing: file \"" ++ fpath ++ "\" doesn't exist. Cannot continue.") str <- readFile fpath case parser str of ParseFailed e -> do let (lineNo, message) = locatedErrorMsg e dieWithLocation fpath lineNo message ParseOk ws x -> do mapM_ warn ws return x -- |Parse the given package file. readPackageDescription :: FilePath -> IO PackageDescription readPackageDescription = readAndParseFile parseDescription readHookedBuildInfo :: FilePath -> IO HookedBuildInfo readHookedBuildInfo = readAndParseFile parseHookedBuildInfo parseDescription :: String -> ParseResult PackageDescription parseDescription inp = do (st:sts) <- splitStanzas inp pkg <- foldM (parseBasicStanza basicStanzaFields) emptyPackageDescription st exes <- mapM parseExecutableStanza sts return pkg{executables=exes} where -- The basic stanza, with library building info parseBasicStanza ((StanzaField name _ set):fields) pkg (lineNo, f, val) | name == f = set lineNo val pkg | otherwise = parseBasicStanza fields pkg (lineNo, f, val) {- , listField "exposed-modules" text parseModuleNameQ (\p -> maybe [] exposedModules (library p)) (\xs pkg -> let lib = fromMaybe emptyLibrary (library pkg) in pkg{library = Just lib{exposedModules=xs}}) -} parseBasicStanza [] pkg (lineNo, f, val) | "exposed-modules" == f = do mods <- runP lineNo f (parseOptCommaList parseModuleNameQ) val return pkg{library=Just lib{exposedModules=mods}} | otherwise = do bi <- parseBInfoField binfoFields (libBuildInfo lib) (lineNo, f, val) return pkg{library=Just lib{libBuildInfo=bi}} where lib = fromMaybe emptyLibrary (library pkg) parseExecutableStanza st@((lineNo, "executable",eName):_) = case lookupField "main-is" st of Just (_,_) -> foldM (parseExecutableField executableStanzaFields) emptyExecutable st Nothing -> syntaxError lineNo $ "No 'Main-Is' field found for " ++ eName ++ " stanza" parseExecutableStanza ((lineNo, f,_):_) = syntaxError lineNo $ "'Executable' stanza starting with field '" ++ f ++ "'" parseExecutableStanza _ = error "This shouldn't happen!" parseExecutableField ((StanzaField name _ set):fields) exe (lineNo, f, val) | name == f = set lineNo val exe | otherwise = parseExecutableField fields exe (lineNo, f, val) parseExecutableField [] exe (lineNo, f, val) = do binfo <- parseBInfoField binfoFields (buildInfo exe) (lineNo, f, val) return exe{buildInfo=binfo} -- ... lookupField :: String -> Stanza -> Maybe (LineNo,String) lookupField x sts = lookup x (map (\(n,f,v) -> (f,(n,v))) sts) parseHookedBuildInfo :: String -> ParseResult HookedBuildInfo parseHookedBuildInfo inp = do stanzas@(mLibStr:exes) <- splitStanzas inp mLib <- parseLib mLibStr biExes <- mapM parseExe (maybe stanzas (const exes) mLib) return (mLib, biExes) where parseLib :: Stanza -> ParseResult (Maybe BuildInfo) parseLib (bi@((_, inFieldName, _):_)) | map toLower inFieldName /= "executable" = liftM Just (parseBI bi) parseLib _ = return Nothing parseExe :: Stanza -> ParseResult (String, BuildInfo) parseExe ((lineNo, inFieldName, mName):bi) | map toLower inFieldName == "executable" = do bis <- parseBI bi return (mName, bis) | otherwise = syntaxError lineNo "expecting 'executable' at top of stanza" parseExe [] = syntaxError 0 "error in parsing buildinfo file. Expected executable stanza" parseBI :: Stanza -> ParseResult BuildInfo parseBI st = foldM (parseBInfoField binfoFields) emptyBuildInfo st parseBInfoField :: [StanzaField a] -> a -> (LineNo, String, String) -> ParseResult a parseBInfoField ((StanzaField name _ set):fields) binfo (lineNo, f, val) | name == f = set lineNo val binfo | otherwise = parseBInfoField fields binfo (lineNo, f, val) -- ignore "x-" extension fields without a warning parseBInfoField [] binfo (lineNo, 'x':'-':f, _) = return binfo parseBInfoField [] binfo (lineNo, f, _) = do warning $ "Unknown field '" ++ f ++ "'" return binfo -- -------------------------------------------- -- ** Pretty printing writePackageDescription :: FilePath -> PackageDescription -> IO () writePackageDescription fpath pkg = writeFile fpath (showPackageDescription pkg) showPackageDescription :: PackageDescription -> String showPackageDescription pkg = render $ ppFields pkg basicStanzaFields $$ (case library pkg of Nothing -> empty Just lib -> text "exposed-modules" <> colon <+> fsep (punctuate comma (map text (exposedModules lib))) $$ ppFields (libBuildInfo lib) binfoFields) $$ vcat (map ppExecutable (executables pkg)) where ppExecutable exe = space $$ ppFields exe executableStanzaFields $$ ppFields (buildInfo exe) binfoFields ppFields _ [] = empty ppFields pkg' ((StanzaField name get _):flds) = ppField name (get pkg') $$ ppFields pkg' flds ppField name field = text name <> colon <+> field writeHookedBuildInfo :: FilePath -> HookedBuildInfo -> IO () writeHookedBuildInfo fpath pbi = writeFile fpath (showHookedBuildInfo pbi) showHookedBuildInfo :: HookedBuildInfo -> String showHookedBuildInfo (mb_lib_bi, ex_bi) = render $ (case mb_lib_bi of Nothing -> empty Just bi -> ppFields bi binfoFields) $$ vcat (map ppExeBuildInfo ex_bi) where ppExeBuildInfo (name, bi) = space $$ text "executable:" <+> text name $$ ppFields bi binfoFields ppFields _ [] = empty ppFields bi ((StanzaField name get _):flds) = ppField name (get bi) $$ ppFields bi flds -- ------------------------------------------------------------ -- * Sanity Checking -- ------------------------------------------------------------ -- |Sanity check this description file. -- FIX: add a sanity check for missing haskell files? That's why its -- in the IO monad. sanityCheckPackage :: PackageDescription -> IO ([String] -- Warnings ,[String])-- Errors sanityCheckPackage pkg_descr = let libSane = sanityCheckLib (library pkg_descr) nothingToDo = checkSanity (null (executables pkg_descr) && isNothing (library pkg_descr)) "No executables and no library found. Nothing to do." noModules = checkSanity (hasMods pkg_descr) "No exposed modules or executables in this package." allRights = checkSanity (license pkg_descr == AllRightsReserved) "Package is copyright All Rights Reserved" noLicenseFile = checkSanity (null $ licenseFile pkg_descr) "No license-file field." goodCabal = let v = (descCabalVersion pkg_descr) in checkSanity (not $ cabalVersion `withinRange` v) ("This package requires Cabal verion: " ++ (showVersionRange v) ++ ".") in return $ (catMaybes [nothingToDo, noModules, allRights, noLicenseFile] ,catMaybes $ libSane:goodCabal:(checkMissingFields pkg_descr)) -- |Output warnings and errors. Exit if any errors. errorOut :: [String] -- ^Warnings -> [String] -- ^errors -> IO () errorOut warnings errors = do mapM warn warnings when (not (null errors)) $ do pname <- getProgName mapM (hPutStrLn stderr . ((pname ++ ": Error: ") ++)) errors exitWith (ExitFailure 1) toMaybe :: Bool -> a -> Maybe a toMaybe b x = if b then Just x else Nothing checkMissingFields :: PackageDescription -> [Maybe String] checkMissingFields pkg_descr = [missingField (pkgName . package) reqNameName ,missingField (versionBranch .pkgVersion .package) reqNameVersion ] where missingField :: (PackageDescription -> [a]) -- Field accessor -> String -- Name of field -> Maybe String -- error message missingField f n = toMaybe (null (f pkg_descr)) ("Missing field: " ++ n) sanityCheckLib :: Maybe Library -> Maybe String sanityCheckLib ml = ml >>= (\l -> toMaybe (null $ exposedModules l) ("Non-empty library, but empty exposed modules list. " ++ "Cabal may not build this library correctly")) checkSanity :: Bool -> String -> Maybe String checkSanity = toMaybe hasMods :: PackageDescription -> Bool hasMods pkg_descr = null (executables pkg_descr) && maybe True (null . exposedModules) (library pkg_descr) -- ------------------------------------------------------------ -- * Testing -- ------------------------------------------------------------