Add a 'cabal path' command.

cabal-install/src/Distribution/Client/Main.hs

@@ -36,6 +36,7 @@ import Distribution.Client.Setup
   , ReportFlags (..)
   , UploadFlags (..)
   , UserConfigFlags (..)
+  , PathFlags (..)
   , actAsSetupCommand
   , benchmarkCommand
   , buildCommand
@@ -69,6 +70,7 @@ import Distribution.Client.Setup
   , unpackCommand
   , uploadCommand
   , userConfigCommand
+  , pathCommand
   , withRepoContext
   )
 import Distribution.Simple.Setup
@@ -102,6 +104,9 @@ import Distribution.Client.Config
   , loadConfig
   , userConfigDiff
   , userConfigUpdate
+  , defaultCacheDir
+  , defaultLogsDir
+  , defaultStoreDir
   )
 import qualified Distribution.Client.List as List
   ( info
@@ -368,6 +373,7 @@ mainWorker args = do
       , regularCmd reportCommand reportAction
       , regularCmd initCommand initAction
       , regularCmd userConfigCommand userConfigAction
+      , regularCmd pathCommand pathAction
       , regularCmd genBoundsCommand genBoundsAction
       , regularCmd CmdOutdated.outdatedCommand CmdOutdated.outdatedAction
       , wrapperCmd hscolourCommand hscolourVerbosity hscolourDistPref
@@ -1320,3 +1326,14 @@ manpageAction commands flags extraArgs _ = do
           then dropExtension pname
           else pname
   manpageCmd cabalCmd commands flags
+
+pathAction :: PathFlags -> [String] -> Action
+pathAction pathflags _extraArgs _globalFlags = do
+  let verbosity  = fromFlag (pathVerbosity pathflags)
+  cfg <- loadConfig verbosity mempty
+  putStrLn . ("cache-dir: "++) =<< maybe defaultCacheDir pure
+    (flagToMaybe $ globalCacheDir $ savedGlobalFlags cfg)
+  putStrLn . ("logs-dir: "++) =<< maybe defaultLogsDir pure
+    (flagToMaybe $ globalLogsDir $ savedGlobalFlags cfg)
+  putStrLn . ("store-dir: "++) =<< maybe defaultStoreDir pure
+    (flagToMaybe $ globalStoreDir $ savedGlobalFlags cfg)

cabal-install/src/Distribution/Client/Setup.hs

@@ -85,6 +85,8 @@ module Distribution.Client.Setup
   , cleanCommand
   , copyCommand
   , registerCommand
+  , PathFlags (..)
+  , pathCommand
   , liftOptions
   , yesNoOpt
   ) where
@@ -3322,6 +3324,42 @@ userConfigCommand =
 
 -- ------------------------------------------------------------
 
+-- * Dirs
+
+-- ------------------------------------------------------------
+
+data PathFlags = PathFlags {
+  pathVerbosity   :: Flag Verbosity
+  } deriving Generic
+
+instance Monoid PathFlags where
+  mempty = PathFlags {
+    pathVerbosity   = toFlag normal
+    }
+  mappend = (<>)
+
+instance Semigroup PathFlags where
+  (<>) = gmappend
+
+pathCommand :: CommandUI PathFlags
+pathCommand = CommandUI {
+  commandName         = "path",
+  commandSynopsis     = "Display the directories used by cabal",
+  commandDescription  = Just $ \_ -> wrapText $
+       "This command prints the directories that are used by cabal,"
+    ++ " taking into account the contents of the configuration file and any"
+    ++ " environment variables.",
+
+  commandNotes        = Nothing,
+  commandUsage        = \pname -> "Usage: " ++ pname ++ " path\n",
+  commandDefaultFlags = mempty,
+  commandOptions      = \ _ -> [
+      optionVerbosity pathVerbosity (\v flags -> flags { pathVerbosity = v })]
+  }
+
+
+-- ------------------------------------------------------------
+
 -- * GetOpt Utils
 
 -- ------------------------------------------------------------