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Command line flag parser for Haskell, conceptually very similar to Google's gflags

License: Apache License 2.0

Haskell 94.92% Shell 5.08%

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effeerre mbacz qnikst deepfire mgajda phadej hardentoo charles37

hflags's Issues

last defineFlag in a module is not precessed

with ghc 7.8.4, a dummy defineFlag (or a return []) is needed.
Seems the same issue as http://hackage.haskell.org/package/QuickCheck-2.7.6/docs/Test-QuickCheck-All.html#v:quickCheckAll

Test case:

{-# LANGUAGE TemplateHaskell #-}
module Main where
import HFlags

defineFlag "f" True "A flag."
return []
--defineFlag "g" True "Another  flag."

main = do
  _ <- $initHFlags "flags demo"
  print Main.flags_f

Without the return [] or the commented out flag definition, accessing Main.flags_f results in a runtime error.

I don't know enough of TH to decide whether it is a ghc bug (it looks like it), but even if it is a ghc problem, mentioning the workaround as quickcheck does would be good. I'd never have figured this out without help from mailing lists.

make it possible to use environment variables not starting with `HFLAGS_`

hi,

i have not used hflags in the real world yet, so i certainly might have missed it, but i can't find a solution to my problems looking at the api.

i often need to interact with environment variables that can also be set as cmdline arguments. i think it's an implementation detail, that hflags is parsing the arguments, so i'd like to either (more flexible) specify the name of the environment variable to consider or remove/change the HFLAGS_ prefix.

(i also don't like that environment variables are not all uppercase, but that's a side remark only. as is, that it's not clearly stated, whether the cmdline arguments or the environment takes precedence.)

envvars should work even if they are all uppercase

Please set correct license tag in cabal file

I suppose the license for this package should be Apache-2.0 instead of OtherLicense.

SimpleExample.hs does not compile

When I try to run SimpleExample.hs I get the error:

Not in scope: 'HFlags.arguments'

I am running ghc 7.4.1

GHC 8.0.1 compilation error?

I get the following error when compiling with GHC 8.0.1 release:

Preprocessing library hflags-0.4.1...
[1 of 1] Compiling HFlags           ( HFlags.hs, dist/build/HFlags.o )
HFlags.hs:406:42: error:
    • Ambiguous type variable ‘b0’ arising from a use of ‘show’
      prevents the constraint ‘(Show b0)’ from being solved.
      Relevant bindings include
        dupe :: [(b0, [Char])] (bound at HFlags.hs:405:6)
      Probable fix: use a type annotation to specify what ‘b0’ should be.
      These potential instances exist:
        instance Show NestedAtomically
          -- Defined in ‘Control.Exception.Base’
        instance Show NoMethodError -- Defined in ‘Control.Exception.Base’
        instance Show NonTermination -- Defined in ‘Control.Exception.Base’
        ...plus 97 others
        ...plus 88 instances involving out-of-scope types
        (use -fprint-potential-instances to see them all)
    • In the second argument of ‘(++)’, namely ‘(show $ map fst dupe)’
      In the second argument of ‘(++)’, namely
        ‘", modules: " ++ (show $ map fst dupe)’
      In the second argument of ‘(++)’, namely
        ‘(snd $ head dupe) ++ ", modules: " ++ (show $ map fst dupe)’
HFlags.hs:409:27: error:
    • The constructor ‘InstanceD’ should have 4 arguments, but has been given 3
    • In the pattern: InstanceD _ (AppT _ inst) _
      In an equation for ‘instanceToFlagData’:
          instanceToFlagData (InstanceD _ (AppT _ inst) _)
            = [| getFlagData (undefined :: $(return inst)) |]
              pending(rn) [<splice, return inst>]
      In an equation for ‘getFlagsData’:
          getFlagsData
            = do { ClassI _ instances <- reify ''Flag;
                   case dupes instances of {
                     [] -> return ()
                     (dupe : _)
                       -> fail
                            ("Multiple definition of flag "
                             ++ (snd $ head dupe) ++ ", modules: " ++ (show $ map fst dupe)) };
                   listE $ map instanceToFlagData instances }
            where
                instanceToFlagData (InstanceD _ (AppT _ inst) _)
                  = [| getFlagData (undefined :: $(return inst)) |]
                    pending(rn) [<splice, return inst>]
                instanceToFlagData _ = error "Shouldn't happen"
                instanceToModuleNamePair (InstanceD _ (AppT _ (ConT inst)) _)
                  = let ... in (modName, flag)
                instanceToModuleNamePair _ = error "Shouldn't happen"
                dupes instances
                  = filter ((> 1) . length)
                    $ groupBy ((==) `on` snd)
                      $ sortBy (compare `on` snd)
                        $ map instanceToModuleNamePair instances
HFlags.hs:415:33: error:
    • The constructor ‘InstanceD’ should have 4 arguments, but has been given 3
    • In the pattern: InstanceD _ (AppT _ (ConT inst)) _
      In an equation for ‘instanceToModuleNamePair’:
          instanceToModuleNamePair (InstanceD _ (AppT _ (ConT inst)) _)
            = let
                (flagrev, modrev) = span (/= '.') $ reverse $ show inst
                modName = reverse $ drop 1 modrev
                ....
              in (modName, flag)
      In an equation for ‘getFlagsData’:
          getFlagsData
            = do { ClassI _ instances <- reify ''Flag;
                   case dupes instances of {
                     [] -> return ()
                     (dupe : _)
                       -> fail
                            ("Multiple definition of flag "
                             ++ (snd $ head dupe) ++ ", modules: " ++ (show $ map fst dupe)) };
                   listE $ map instanceToFlagData instances }
            where
                instanceToFlagData (InstanceD _ (AppT _ inst) _)
                  = [| getFlagData (undefined :: $(return inst)) |]
                    pending(rn) [<splice, return inst>]
                instanceToFlagData _ = error "Shouldn't happen"
                instanceToModuleNamePair (InstanceD _ (AppT _ (ConT inst)) _)
                  = let ... in (modName, flag)
                instanceToModuleNamePair _ = error "Shouldn't happen"
                dupes instances
                  = filter ((> 1) . length)
                    $ groupBy ((==) `on` snd)
                      $ sortBy (compare `on` snd)
                        $ map instanceToModuleNamePair instances

Make part "from module: ..." optional

Is it possible to get

--favorite_color=COLOR      Your favorite color. (default: Yellow)

instead of

--favorite_color=COLOR      Your favorite color. (default: Yellow, from module: Main)

hflags-0.4.2 does not compile

Trying to hflags with GHC 8.2.1, I get the following error:

Preprocessing library for hflags-0.4.2..
Building library for hflags-0.4.2..
[1 of 1] Compiling HFlags           ( HFlags.hs, dist/build/HFlags.o )

HFlags.hs:190:81: error:
    • Couldn't match type ‘Q Cxt’ with ‘[DerivClauseQ]’
      Expected type: [DerivClauseQ]
        Actual type: CxtQ
    • In the sixth argument of ‘dataD’, namely ‘(cxt [])’
      In a stmt of a 'do' block:
        dataDec <- dataD
                     (cxt []) dataName [] Nothing [normalC dataConstrName []] (cxt [])
      In the expression:
        do (name, short) <- if | 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
           flagType <- case defE of
                         SigE _ flagType -> return $ return flagType
                         _ -> fail
                                "Default value for defineCustomFlag has to be an explicitly typed expression, like (12 :: Int)"
           moduleName <- fmap loc_module location
           ....
    |
190 |      dataDec <- dataD (cxt []) dataName [] Nothing [normalC dataConstrName []] (cxt [])
    |                                                                                 ^^^^^^

Getting non-flag arguments

I'm new to Haskell and am using hflags to parse command line options in my project.
Can you tell me what would be the best way to handle non-flag arguments using this module.
For example:
On typing the following command
hello --print --debug file.txt file2.txt
I want print and debug to appear as variables (which hflags does) and simultaneously [file.txt : file2.txt] to appear in a list

GHC 8.0 release candidate compatibility

Trying to compile with latest GHC 8 release candidate leads to the following error:

HFlags.hs:188:17: error:
    • Couldn't match expected type ‘Q Dec’
                  with actual type ‘CxtQ -> DecQ’
    • Probable cause: ‘dataD’ is applied to too few arguments
      In a stmt of a 'do' block:
        dataDec <- dataD
                     (cxt []) dataName [] [normalC dataConstrName []] []
      In the expression:
        do { (name, short) <- if
                              | 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;
             flagType <- case defE of {
                           SigE _ flagType -> return $ return flagType
                           _ -> fail
                                  "Default value for defineCustomFlag has to be an explicitly typed expression, like (12 :: Int)" };
             moduleName <- fmap loc_module location;
             .... }
      In an equation for ‘defineCustomFlag’:
          defineCustomFlag name' defQ argHelp readQ showQ description
            = do { (name, short) <- if
                                    | length name' == 0
                                    -> fail "Flag's without names are not supported."
                                    | length name' == 1 -> return ...
                                    | length name' == 2 -> return ...
                                    | name' !! 1 == ':' -> return ...
                                    | otherwise -> return ...;
                   defE <- defQ;
                   flagType <- case defE of {
                                 SigE _ flagType -> return $ return flagType
                                 _ -> fail
                                        "Default value for defineCustomFlag has to be an explicitly typed expression, like (12 :: Int)" };
                   .... }

HFlags.hs:188:44: error:
    • Couldn't match expected type ‘Maybe Kind’
                  with actual type ‘[ConQ]’
    • In the fourth argument of ‘dataD’, namely
        ‘[normalC dataConstrName []]’
      In a stmt of a 'do' block:
        dataDec <- dataD
                     (cxt []) dataName [] [normalC dataConstrName []] []
      In the expression:
        do { (name, short) <- if
                              | 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;
             flagType <- case defE of {
                           SigE _ flagType -> return $ return flagType
                           _ -> fail
                                  "Default value for defineCustomFlag has to be an explicitly typed expression, like (12 :: Int)" };
             moduleName <- fmap loc_module location;
             .... }

Looks like Template Haskell type of dataD got a new argument CxtQ.

Would it be possible to upgrade this one?

$initHFlags_

so the user can conveniently ignore arguments without "Warning: A do-notation statement discarded a result of type [String]."

Ignored flag?

Hi. I am attempting to use HFlags and only one of the two flags being defined actually is recognized:

{-# LANGUAGE TemplateHaskell #-}

import HFlags

defineFlag "x" (0.5 :: Double) "x"
defineFlag "y" (1 :: Int) "y"

main = do
  s <- $initHFlags "Testcase"
  print flags_y

This results in a runtime error, "Flag y not found at runtime, look into HFlags-source/examples/package/Tup.hs. Sorry." The "x" flag seems to work fine, it's the "y" flag that doesn't.

This is HFlags-4.0, GHC 7.8.2, on OS X. Perhaps I am doing something wrong?

access the flags in IO

i prefer to have code depending on the environment marked as such. i usually use IO for that.

can one, additionally to flags_flagN :: a generate a ioFlags_flagN :: IO a or similar (maybe with MonadIO constraint). that way i'd feel more confident when using it as i only would have to remember always using the right function and the types will work everything out for me.

Documentation unclear on precedence between envvar and cmdline

Documentation should explicitly state that cmdline flags overwrite any values set by environment variables.