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All Rights Reserved. +-- +-- Licensed under the Apache License, Version 2.0 (the "License"); +-- you may not use this file except in compliance with the License. +-- You may obtain a copy of the License at +-- +-- http://www.apache.org/licenses/LICENSE-2.0 +-- +-- Unless required by applicable law or agreed to in writing, software +-- distributed under the License is distributed on an "AS IS" BASIS, +-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +-- See the License for the specific language governing permissions and +-- limitations under the License. +-- +-- Authors: Mihaly Barasz , Gergely Risko + +{-# LANGUAGE TemplateHaskell #-} +{-# LANGUAGE TypeSynonymInstances #-} +{-# LANGUAGE FlexibleInstances #-} +{-# LANGUAGE NamedFieldPuns #-} + +-- | +-- Module: HFlags +-- License: Apache 2.0 +-- +-- The @HFlags@ library supports easy definition of command line flags, +-- reimplementing the ideas from Google's @gflags@ +-- (). +-- +-- Command line flags can be declared in any file at the toplevel, +-- using 'defineFlag'. At runtime, the actual values are assigned to +-- the toplevel @flags_name@ constants. Those can be used purely +-- throughout the program. +-- +-- At the beginning of the @main@ function, @$(initHFlags "program +-- description")@ has to be called to initialize the flags. All flags +-- will be initialized that are transitively reachable via imports +-- from @main@. This means, that any Haskell package can easily +-- define command line flags with @HFlags@. This feature is +-- demonstrated by +-- . +-- +-- A simple example (more in the +-- directory): +-- +-- > #!/usr/bin/env runhaskell +-- > +-- > {-# LANGUAGE TemplateHaskell #-} +-- > +-- > import HFlags +-- > +-- > defineFlag "name" "Indiana Jones" "Who to greet." +-- > defineFlag "r:repeat" (3 + 4 :: Int) "Number of times to repeat the message." +-- > +-- > main = do s <- $(initHFlags "Simple program v0.1") +-- > sequence_ $ replicate flags_repeat greet +-- > where +-- > greet = putStrLn $ "Hello " ++ flags_name ++ ", very nice to meet you!" +-- +-- At @initHFlags@ time, the library also tries to gather flags out of +-- environment variables. @HFLAGS_verbose=True@ is equivalent to +-- specify --verbose=True. This environment feature only works with +-- long options and the user has to specify a value even for Bools. + +module HFlags ( + -- * Definition of flags + defineCustomFlag, + defineQQFlag, + FlagType(..), + -- * Initialization of flags at runtime + initHFlags) where + +-- TODOs: +-- ?--no* for bools? +-- --help should show the current value if it's different than the default value, so user can test command line args + +import Control.Exception +import Control.Monad +import Data.Char +import Data.Function +import Data.List +import Data.IORef +import Data.Maybe +import qualified Data.Map as Map +import Data.Map (Map, (!)) +import Language.Haskell.TH +import System.Console.GetOpt +import System.Environment +import System.IO +import System.IO.Unsafe +import System.Exit + +import Prelude hiding (catch) + +-- | Data type for storing every property of a flag. +data FlagData = FlagData + { fName :: String + , fShort :: Maybe Char + , fDefValue :: String + , fArgHelp :: String + , fDescription :: String + , fModuleName :: String + , fCheck :: IO () -- ^ function to evaluate in 'initFlags' + -- to force syntax check of the argument. + } + +-- | Every flag the program supports has to be defined through a new +-- phantom datatype and the Flag instance of that datatype. +-- +-- But users of the library shouldn't worry about this class or the +-- implementation details behind these functions, just use the +-- @defineFlag@ Template Haskell function for defining new flags. +class Flag a where + getFlagData :: a -> FlagData + +-- | The most flexible way of defining a flag. For an example see +-- . +-- For most things 'defineFlag' should be enough instead. +-- +-- The parameters: +-- +-- * name of the flag (@l:long@ syntax if you want to have the short option @l@ for this flag), +-- +-- * quasiquoted and type signed default value, +-- +-- * help string for the argument, +-- +-- * read function, quasiquoted, +-- +-- * show function, quasiquoted, +-- +-- * help string for the flag. +defineCustomFlag :: String -> ExpQ -> String -> ExpQ -> ExpQ -> String -> Q [Dec] +defineCustomFlag name' defQ argHelp readQ showQ description = + do (name, short) <- case () of + () | length name' == 0 -> fail "Flag's without names are not supported." + | length name' == 1 -> return (name', Just $ head name') + | length name' == 2 -> return (name', Nothing) + | name' !! 1 == ':' -> return (drop 2 name', Just $ head name') + | otherwise -> return (name', Nothing) + defE <- defQ + case defE of + SigE _ _ -> return () + _ -> fail "Default value for defineCustomFlag has to be an explicitly typed expression, like (12 :: Int)" + moduleName <- fmap loc_module location + let accessorName = mkName $ "flags_" ++ name + let dataName = mkName $ "HFlag_" ++ name + dataDec <- return $ DataD [] dataName [] [] [] + instanceDec <- instanceD + (return []) + (appT (conT ''Flag) (conT dataName)) + [funD 'getFlagData [clause [wildP] + (normalB + [| FlagData + name + short + $(appE showQ defQ) + argHelp + description + moduleName + (evaluate $(varE accessorName) >> return ()) + |]) []]] + flagPragmaDec <- return $ PragmaD $ InlineP accessorName $ InlineSpec False False Nothing + flagDec <- funD accessorName [clause [] (normalB [| case True of + True -> $(appE readQ [| lookupFlag name moduleName |]) + False -> $(defQ) |]) []] + return [dataDec, instanceDec, flagPragmaDec, flagDec] + +-- | This just forwards to 'defineCustomFlag' with @[| read |]@ and +-- @[| show |]@. Useful for flags where the type is not an instance +-- of 'FlagType'. For examples, see +-- . +-- +-- The parameters: +-- +-- * name of the flag (@l:long@ syntax if you want to have the short option @l@ for this flag),, +-- +-- * quasiquoted and type signed default value, +-- +-- * help string for the argument, +-- +-- * help string for the flag. +defineQQFlag :: String -> ExpQ -> String -> String -> Q [Dec] +defineQQFlag name defQ argHelp description = + defineCustomFlag name defQ argHelp [| read |] [| show |] description + +-- | Class of types for which the easy 'defineFlag' syntax is supported. +class FlagType t where + -- | The @defineFlag@ function defines a new flag. + -- + -- The parameters: + -- + -- * name of the flag (@l:long@ syntax if you want to have the short option @l@ for this flag),, + -- + -- * default value, + -- + -- * help string for the flag. + defineFlag :: String -> t -> String -> Q [Dec] + +boolShow :: Bool -> String +boolShow True = "true" +boolShow False = "false" + +boolRead :: String -> Bool +boolRead = boolRead' . map toLower + where + boolRead' ('y':_) = True + boolRead' ('t':_) = True + boolRead' ('1':_) = True + boolRead' ('n':_) = False + boolRead' ('f':_) = False + boolRead' ('0':_) = False + boolRead' s = error $ "Unable to parse string as boolean: " ++ s + +instance FlagType Bool where + defineFlag n v = defineCustomFlag n [| v :: Bool |] "BOOL" [| boolRead |] [| boolShow |] + +instance FlagType Int where + defineFlag n v = defineQQFlag n [| v :: Int |] "INT" + +instance FlagType Integer where + defineFlag n v = defineQQFlag n [| v :: Integer |] "INTEGER" + +instance FlagType String where + defineFlag n v = defineCustomFlag n [| v :: String |] "STRING" [| id |] [| id |] + +instance FlagType Double where + defineFlag n v = defineQQFlag n (sigE (litE (RationalL (toRational v))) [t| Double |] ) "DOUBLE" + +-- | A global "IORef" for the communication between @initHFlags@ and +-- @flag_*@. This is a map between flag name and current value. +{-# NOINLINE globalHFlags #-} +globalHFlags :: IORef (Maybe (Map String String)) +globalHFlags = unsafePerformIO $ newIORef Nothing + +lookupFlag :: String -> String -> String +lookupFlag fName fModuleName = unsafePerformIO $ do + flags <- readIORef globalHFlags + case flags of + Just flagmap -> return $ flagmap ! fName + Nothing -> error $ "Flag " ++ fName ++ " (from module: " ++ fModuleName ++ ") used before calling initHFlags." + +-- | Initializes @globalHFlags@ and returns the non-option arguments. +initFlags :: String -> [FlagData] -> [String] -> IO [String] +initFlags progDescription flags args = do + doHelp + let (opts, nonopts, errs) | doUndefok = (\(a,b,_,c) -> (a,b,c)) $ getOpt' Permute getOptFlags args + | otherwise = getOpt Permute getOptFlags args + when (not $ null errs) $ do + mapM_ (hPutStrLn stderr) errs + exitFailure + let defaults = map (\FlagData { fName, fDefValue } -> (fName, fDefValue)) flags + env <- getEnvironment + let envDefaults = map (mapFst (fromJust . stripPrefix "HFLAGS_")) $ filter ((isPrefixOf "HFLAGS_") . fst) env + writeIORef globalHFlags $ Just $ Map.fromList $ defaults ++ envDefaults ++ opts + mapM_ forceFlag flags + return nonopts + where + mapFst f (a, b) = (f a, b) + helpOption = Option "h" ["help", "usage", "version"] (NoArg ("", "")) "Display help and version information." + doHelp = case getOpt Permute [helpOption] args of + ([], _, _) -> return () + _ -> do putStrLn $ usageInfo (progDescription ++ "\n") (helpOption:undefokOption:getOptFlags) + exitFailure + + undefokOption = Option "" ["undefok"] (NoArg ("", "")) "Whether to fail on unrecognized command line options." + doUndefok = case getOpt Permute [undefokOption] args of + ([], _, _) -> False + _ -> True + + flagToGetOptArgDescr FlagData { fName, fArgHelp } + | fArgHelp == "BOOL" = OptArg (\a -> (fName, maybe "True" id a)) fArgHelp + | otherwise = ReqArg (\a -> (fName, a)) fArgHelp + + -- compute GetOpt compatible [Option] structure from flags ([FlagData]) + getOptFlags = flip map flags $ \flagData@(FlagData { fName, fShort, fDefValue, fDescription, fModuleName }) -> + Option (maybeToList fShort) [fName] (flagToGetOptArgDescr flagData) + (fDescription ++ " (default: " ++ fDefValue ++ ", from module: " ++ fModuleName ++ ")") + + forceFlag FlagData { fName, fModuleName, fCheck } = + fCheck `catch` + (\e -> error $ + "Error while parsing argument for flag: " ++ fName ++ + ", value: " ++ lookupFlag fName fModuleName ++ + ", error: " ++ show (e :: ErrorCall)) + +-- | Has to be called from the main before doing anything else: +-- +-- @ +-- main = do args <- $(initHFlags "Simple program v0.1") +-- ... +-- @ +-- +-- Internally, it uses Template Haskell trickery to gather all the +-- instances of the Flag class and then generates a call to +-- @initFlags@ with the appropriate data gathered together from those +-- instances to a list. +-- +-- Type after splicing is @IO [String]@. +initHFlags :: String -> ExpQ -- IO [String] +initHFlags progDescription = do + ClassI _ instances <- reify ''Flag + case dupes instances of + [] -> return () + (dupe:_) -> fail ("Multiple definition of flag " ++ (snd $ head dupe) ++ + ", modules: " ++ (show $ map fst dupe)) + [| getArgs >>= initFlags progDescription $(listE $ map instanceToOptTuple instances ) |] + where + instanceToOptTuple (InstanceD _ (AppT _ inst) _) = [| getFlagData (undefined :: $(return inst)) |] + instanceToOptTuple _ = error "Shouldn't happen" + instanceToModuleNamePair (InstanceD _ (AppT _ (ConT inst)) _) = + let (flagrev, modrev) = span (/= '.') $ reverse $ show inst + modName = reverse $ drop 1 modrev + flag = drop 1 $ dropWhile (/= '_') $ reverse $ flagrev + in (modName, flag) + instanceToModuleNamePair _ = error "Shouldn't happen" + dupes instances = filter ((>1) . length) $ + groupBy ((==) `on` snd) $ + sortBy (compare `on` snd) $ + map instanceToModuleNamePair instances diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/examples/ComplexExample.hs b/examples/ComplexExample.hs new file mode 100644 --- /dev/null +++ b/examples/ComplexExample.hs @@ -0,0 +1,72 @@ +#!/usr/bin/env runhaskell + +{-# LANGUAGE TemplateHaskell #-} + +import Control.Monad +import System.Exit + +import HFlags + +-- For flags with a simple type (technically speaking, for instances +-- of FlagType, see `:info FlagType' in GHCi), defining a new flag is +-- very straightforward: +defineFlag "name" "Indiana Jones" "Who to greet." +-- There is a special syntax to support short options, like `d' here. +-- Also, for the Bool options the argument is not mandatory, if the +-- user just runs the program with -d or --dry_run, flags_dru_run will +-- be set to True. +defineFlag "d:dry_run" False "Don't print anything, just exit." +-- For integral types you have to explicitly define Int or Integer. +defineFlag "repeat" (3 + 4 :: Int) "Number of times to repeat the message." + +-- For flags with a more complex type, where the existing Read and +-- Show is suitable for parsing of the argument value, you can use the +-- defineQQFlag syntax. Here, the QQ is mnemonic for QuasiQuoter, +-- because you have to quasiquote the default value, and type sign it +-- inside the quasiquote. Also, you have to provide the name of the +-- type for --help generation. +defineQQFlag "numbers_to_sum" [| [1,2,3,4,5] :: [Int] |] "INT_LIST" "Print the sum of these numbers." + +-- This works quite well for simple enums too! +data Color = Red | Yellow | Green deriving (Show, Read) +defineQQFlag "favorite_color" [| Yellow :: Color |] "COLOR" "Your favorite color." + +-- Sometimes the default read or show instance is not good enough for +-- your needs. In that case you can use defineCustomFlag to override +-- those functions. +data Language = English | Hungarian +defineCustomFlag "language" [| English :: Language |] "en|hu" + [| \s -> case s of + "en" -> English + "hu" -> Hungarian + _ -> error $ "Unknown language: " ++ s + |] + [| \l -> case l of + English -> "en" + Hungarian -> "hu" + |] + "Language of the greeting." + +-- You can also do simple range checks with this. +defineCustomFlag "percent" [| 100 :: Double |] "PERCENTAGE" + [| \s -> let p = read s + in if 0.0 <= p && p <= 100.0 + then p + else error "Percentage value has to be between 0 and 100." + |] + [| show |] + "Print first percent percentage of the message." + +main = do + _ <- $(initHFlags "HFlags example program v0.1") + when (flags_dry_run) $ exitSuccess + forM_ [1..flags_repeat] (const greet) + putStrLn $ "IIRC, your favorite color is " ++ show flags_favorite_color ++ "." + where + s = show (sum flags_numbers_to_sum) + percentPutStrLn 0 _ = return () + percentPutStrLn p str = let n = ceiling $ fromIntegral (length str) * p / 100.0 + in putStrLn $ take n str + greet = percentPutStrLn flags_percent $ case flags_language of + English -> "Hello " ++ flags_name ++ ", very nice to meet you, the sum is " ++ s ++ "!" + Hungarian -> "Szia " ++ flags_name ++ ", orvendek a talalkozasnak, a szamok osszege " ++ s ++ "!" diff --git a/examples/ImportExample.hs b/examples/ImportExample.hs new file mode 100644 --- /dev/null +++ b/examples/ImportExample.hs @@ -0,0 +1,9 @@ +#!/usr/bin/env runhaskell + +{-# LANGUAGE TemplateHaskell #-} + +import HFlags +import X.B + +main = do _ <- $(initHFlags "Importing example v0.1") + print $ b diff --git a/examples/SimpleExample.hs b/examples/SimpleExample.hs new file mode 100644 --- /dev/null +++ b/examples/SimpleExample.hs @@ -0,0 +1,13 @@ +#!/usr/bin/env runhaskell + +{-# LANGUAGE TemplateHaskell #-} + +import HFlags + +defineFlag "name" "Indiana Jones" "Who to greet." +defineFlag "repeat" (3 + 4 :: Int) "Number of times to repeat the message." + +main = do s <- $(initHFlags "Simple program v0.1") + sequence_ $ replicate flags_repeat greet + where + greet = putStrLn $ "Hello " ++ flags_name ++ ", very nice to meet you!" diff --git a/examples/X/B.hs b/examples/X/B.hs new file mode 100644 --- /dev/null +++ b/examples/X/B.hs @@ -0,0 +1,9 @@ +module X.B (b) where + +import qualified X.Y_Y.A as A + +-- to test collision detection +-- import HFlags +-- defineFlag "verbose" True "Whether debug output should be printed." + +b = A.flags_verbose diff --git a/examples/X/Y_Y/A.hs b/examples/X/Y_Y/A.hs new file mode 100644 --- /dev/null +++ b/examples/X/Y_Y/A.hs @@ -0,0 +1,7 @@ +{-# LANGUAGE TemplateHaskell #-} + +module X.Y_Y.A where + +import HFlags + +defineFlag "verbose" True "Whether debug output should be printed." diff --git a/hflags.cabal b/hflags.cabal new file mode 100644 --- /dev/null +++ b/hflags.cabal @@ -0,0 +1,76 @@ +name: hflags +version: 0.1 +license: OtherLicense +license-file: COPYING +author: Mihaly Barasz , Gergely Risko +maintainer: Gergely Risko +build-type: Simple +cabal-version: >= 1.6 +category: Console +stability: provisional +homepage: http://github.com/errge/hflags +bug-reports: mailto:errge@google.com + +synopsis: Command line flag parser, very similar to Google's gflags +description: + The @HFlags@ library supports easy definition of command line flags, + reimplementing the ideas from Google's @gflags@ + (). + . + Command line flags can be declared in any file at the toplevel, + using 'defineFlag'. At runtime, the actual values are assigned to + the toplevel @flags_name@ constants. Those can be used purely + throughout the program. + . + At the beginning of the @main@ function, @$(initHFlags "program + description")@ has to be called to initialize the flags. All flags + will be initialized that are transitively reachable via imports from + @main@. This means, that any Haskell package can easily define + command line flags with @HFlags@. This feature is demonstrated by + . + . + A simple example (more in the + directory): + . + @ + \#!\/usr\/bin\/env runhaskell + . + {-\# LANGUAGE TemplateHaskell \#-} + . + import HFlags + . + 'defineFlag' \"name\" \"Indiana Jones\" \"Who to greet.\" + 'defineFlag' \"r:repeat\" (3 + 4 :: Int) \"Number of times to repeat the message.\" + . + main = do s <- $(initHFlags \"Simple program v0.1\") + sequence_ $ replicate flags_repeat greet + where + greet = putStrLn $ \"Hello \" ++ flags_name ++ \", very nice to meet you!\" + @ + . + At @initHFlags@ time, the library also tries to gather flags out of + environment variables. @HFLAGS_verbose=True@ is equivalent to + specify --verbose=True. This environment feature only works with + long options and the user has to specify a value even for Bools. + +extra-source-files: + examples/ComplexExample.hs + examples/ImportExample.hs + examples/SimpleExample.hs + examples/X/B.hs + examples/X/Y_Y/A.hs + +source-repository head + type: git + location: http://github.com/errge/hflags + +library + ghc-options: -Wall + + build-depends: + base >= 4.5 && < 5 + , containers >= 0.4 + , template-haskell >= 2.7 + + exposed-modules: + HFlags