Fix typo (backport #9770)

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

@@ -3362,6 +3362,73 @@ userConfigCommand =
 
 -- ------------------------------------------------------------
 
+-- * Dirs
+
+-- ------------------------------------------------------------
+
+-- | A path that can be retrieved by the @cabal path@ command.
+data Path
+  = PathCacheDir
+  | PathLogsDir
+  | PathStoreDir
+  | PathConfigFile
+  | PathInstallDir
+  deriving (Eq, Ord, Show, Enum, Bounded)
+
+-- | The configuration name for this path.
+pathName :: Path -> String
+pathName PathCacheDir = "cache-dir"
+pathName PathLogsDir = "logs-dir"
+pathName PathStoreDir = "store-dir"
+pathName PathConfigFile = "config-file"
+pathName PathInstallDir = "installdir"
+
+data PathFlags = PathFlags
+  { pathVerbosity :: Flag Verbosity
+  , pathDirs :: Flag [Path]
+  }
+  deriving (Generic)
+
+instance Monoid PathFlags where
+  mempty =
+    PathFlags
+      { pathVerbosity = toFlag normal
+      , pathDirs = toFlag []
+      }
+  mappend = (<>)
+
+instance Semigroup PathFlags where
+  (<>) = gmappend
+
+pathCommand :: CommandUI PathFlags
+pathCommand =
+  CommandUI
+    { commandName = "path"
+    , commandSynopsis = "Display paths 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 = \_ ->
+        map pathOption [minBound .. maxBound]
+          ++ [optionVerbosity pathVerbosity (\v flags -> flags{pathVerbosity = v})]
+    }
+  where
+    pathOption s =
+      option
+        []
+        [pathName s]
+        ("Print " <> pathName s)
+        pathDirs
+        (\v flags -> flags{pathDirs = Flag $ concat (flagToList (pathDirs flags) ++ flagToList v)})
+        (noArg (Flag [s]))
+
+-- ------------------------------------------------------------
+
 -- * GetOpt Utils
 
 -- ------------------------------------------------------------