Add Option to format long options with equals sign

.gitignore

@@ -5,3 +5,5 @@
 cabal.project.local
 .cabal-sandbox/
 cabal.sandbox.config
+
+.ghc.environment.*

optparse-applicative.cabal

@@ -42,7 +42,7 @@ extra-source-files:  CHANGELOG.md
 
 homepage:            https://github.com/pcapriotti/optparse-applicative
 bug-reports:         https://github.com/pcapriotti/optparse-applicative/issues
-tested-with: 
+tested-with:
   GHC==7.0.4,
   GHC==7.2.2,
   GHC==7.4.2,

src/Options/Applicative.hs

@@ -195,6 +195,7 @@ module Options.Applicative (
   noBacktrack,
   subparserInline,
   columns,
+  helpLongEquals,
   defaultPrefs,
 
   -- * Completions

src/Options/Applicative/Builder.hs

@@ -85,6 +85,7 @@ module Options.Applicative.Builder (
   noBacktrack,
   subparserInline,
   columns,
+  helpLongEquals,
   prefs,
   defaultPrefs,
 
@@ -500,6 +501,11 @@ subparserInline = PrefsMod $ \p -> p { prefBacktrack = SubparserInline }
 columns :: Int -> PrefsMod
 columns cols = PrefsMod $ \p -> p { prefColumns = cols }
 
+-- | Show equals sign, rather than space, in usage and help text for options with
+-- long names.
+helpLongEquals :: PrefsMod
+helpLongEquals = PrefsMod $ \p -> p { prefHelpLongEquals = True }
+
 -- | Create a `ParserPrefs` given a modifier
 prefs :: PrefsMod -> ParserPrefs
 prefs m = applyPrefsMod m base
@@ -510,7 +516,8 @@ prefs m = applyPrefsMod m base
       , prefShowHelpOnError = False
       , prefShowHelpOnEmpty = False
       , prefBacktrack = Backtrack
-      , prefColumns = 80 }
+      , prefColumns = 80
+      , prefHelpLongEquals = False }
 
 -- Convenience shortcuts
 

src/Options/Applicative/Common.hs

@@ -22,6 +22,7 @@ module Options.Applicative.Common (
   Parser,
   liftOpt,
   showOption,
+  showOptionEquals,
 
   -- * Program descriptions
   --
@@ -65,6 +66,12 @@ showOption :: OptName -> String
 showOption (OptLong n) = "--" ++ n
 showOption (OptShort n) = '-' : [n]
 
+-- | Like 'showOption', but puts an equals sign or a space after long options if the
+-- 'ParserPrefs' indicate we should do so.
+showOptionEquals :: ParserPrefs -> OptName -> String
+showOptionEquals prefs (OptLong n) = "--" ++ n ++ (if prefHelpLongEquals prefs then "=" else "")
+showOptionEquals _ (OptShort n) = '-' : [n]
+
 optionNames :: OptReader a -> [OptName]
 optionNames (OptReader names _ _) = names
 optionNames (FlagReader names _) = names

src/Options/Applicative/Extra.hs

@@ -258,7 +258,7 @@ parserFailure pprefs pinfo msg ctx = ParserFailure $ \progn ->
             -- reader also ensure that it can be immediately
             -- reachable from where the error was given.
             opt_completions hinfo opt = case optMain opt of
-              OptReader ns _ _ -> fmap showOption ns
+              OptReader ns _ _ -> fmap (showOptionEquals pprefs) ns
               FlagReader ns _  -> fmap showOption ns
               ArgReader _      -> []
               CmdReader _ ns _  | hinfoUnreachableArgs hinfo

src/Options/Applicative/Help/Core.hs

@@ -37,8 +37,16 @@ optDesc :: ParserPrefs -> OptDescStyle -> OptHelpInfo -> Option a -> (Chunk Doc,
 optDesc pprefs style info opt =
   let ns = optionNames $ optMain opt
       mv = stringChunk $ optMetaVar opt
-      descs = map (string . showOption) (sort ns)
-      desc  = listToChunk (intersperse (descSep style) descs) <<+>> mv
+      has_arg = case mv of
+        Chunk Nothing -> True
+        _ -> False
+      descs | has_arg = map (string . showOption) (sort ns)
+            | otherwise = map (string . showOptionEquals pprefs) (sort ns)
+      isLong (OptLong _) = True
+      isLong _ = False
+      has_equals = any isLong ns && prefHelpLongEquals pprefs
+      desc | has_equals = listToChunk (intersperse (descSep style) descs) <> mv
+           | otherwise = listToChunk (intersperse (descSep style) descs) <<+>> mv
       show_opt
         | optVisibility opt == Hidden
         = descHidden style

src/Options/Applicative/Types.hs

@@ -117,6 +117,9 @@ data ParserPrefs = ParserPrefs
                                   -- subcommand fails (default: Backtrack)
   , prefColumns :: Int            -- ^ number of columns in the terminal, used to
                                   -- format the help page (default: 80)
+  , prefHelpLongEquals :: Bool    -- ^ when displaying long names in usage and help,
+                                  -- use an '=' sign for long names, rather than a
+                                  -- single space (default: False)
   } deriving (Eq, Show)
 
 data OptName = OptShort !Char

tests/long_equals.err.txt

@@ -0,0 +1,6 @@
+Usage: long_equals (-i|-j|--intval=|--intval2=ARG)
+
+Available options:
+  -i,-j,--intval=,--intval2=ARG
+                           integer value
+  -h,--help                Show this help text

tests/test.hs

@@ -202,6 +202,17 @@ prop_nested_optional_help = once $
       i = info (p <**> helper) idm
   in checkHelpText "nested_optional" i ["--help"]
 
+prop_long_equals :: Property
+prop_long_equals = once $
+  let p :: Parser String
+      p = option auto (long "intval"
+                       <> short 'j'
+                       <> long "intval2"
+                       <> short 'i'
+                       <> help "integer value")
+      i = info (p <**> helper) fullDesc
+  in checkHelpTextWith ExitSuccess (prefs helpLongEquals) "long_equals" i ["--help"]
+
 prop_nested_fun :: Property
 prop_nested_fun = once $
   let p :: Parser (String, Maybe (String, Maybe String))