improve createDirectoryUnder to allow alternate top directories

This should not change the behavior of it, unless there are multiple top
directories, and then it should behave the same as if there was a single
top directory that was actually above the directory to be created.

Sponsored-by: Dartmouth College's Datalad project

Utility/Directory/Create.hs

@@ -31,10 +31,10 @@ import qualified Utility.RawFilePath as R
 import Utility.PartialPrelude
 
 {- Like createDirectoryIfMissing True, but it will only create
- - missing parent directories up to but not including the directory
- - in the first parameter.
+ - missing parent directories up to but not including a directory
+ - from the first parameter.
  -
- - For example, createDirectoryUnder "/tmp/foo" "/tmp/foo/bar/baz"
+ - For example, createDirectoryUnder ["/tmp/foo"] "/tmp/foo/bar/baz"
  - will create /tmp/foo/bar if necessary, but if /tmp/foo does not exist,
  - it will throw an exception.
  -
@@ -45,40 +45,43 @@ import Utility.PartialPrelude
  - FilePath (or the same as it), it will fail with an exception
  - even if the second FilePath's parent directory already exists.
  -
- - Either or both of the FilePaths can be relative, or absolute.
+ - The FilePaths can be relative, or absolute. 
  - They will be normalized as necessary.
  -
  - Note that, the second FilePath, if relative, is relative to the current
- - working directory, not to the first FilePath.
+ - working directory.
  -}
-createDirectoryUnder :: RawFilePath -> RawFilePath -> IO ()
-createDirectoryUnder topdir dir =
-	createDirectoryUnder' topdir dir R.createDirectory
+createDirectoryUnder :: [RawFilePath] -> RawFilePath -> IO ()
+createDirectoryUnder topdirs dir =
+	createDirectoryUnder' topdirs dir R.createDirectory
 
 createDirectoryUnder'
 	:: (MonadIO m, MonadCatch m)
-	=> RawFilePath
+	=> [RawFilePath]
 	-> RawFilePath
 	-> (RawFilePath -> m ())
 	-> m ()
-createDirectoryUnder' topdir dir0 mkdir = do
-	p <- liftIO $ relPathDirToFile topdir dir0
-	let dirs = P.splitDirectories p
-	-- Catch cases where the dir is not beneath the topdir.
+createDirectoryUnder' topdirs dir0 mkdir = do
+	relps <- liftIO $ forM topdirs $ \topdir -> relPathDirToFile topdir dir0
+	let relparts = map P.splitDirectories relps
+	-- Catch cases where dir0 is not beneath a topdir.
 	-- If the relative path between them starts with "..",
 	-- it's not. And on Windows, if they are on different drives,
 	-- the path will not be relative.
-	if headMaybe dirs == Just ".." || P.isAbsolute p
-		then liftIO $ ioError $ customerror userErrorType
-			("createDirectoryFrom: not located in " ++ fromRawFilePath topdir)
-		-- If dir0 is the same as the topdir, don't try to create
-		-- it, but make sure it does exist.
-		else if null dirs
-			then liftIO $ unlessM (doesDirectoryExist (fromRawFilePath topdir)) $
-				ioError $ customerror doesNotExistErrorType
-					"createDirectoryFrom: does not exist"
-			else createdirs $
-				map (topdir P.</>) (reverse (scanl1 (P.</>) dirs))
+	let notbeneath = \(_topdir, (relp, dirs)) -> 
+		headMaybe dirs /= Just ".." && not (P.isAbsolute relp)
+	case filter notbeneath $ zip topdirs (zip relps relparts) of
+		((topdir, (_relp, dirs)):_)
+			-- If dir0 is the same as the topdir, don't try to
+			-- create it, but make sure it does exist.
+			| null dirs ->
+				liftIO $ unlessM (doesDirectoryExist (fromRawFilePath topdir)) $
+					ioError $ customerror doesNotExistErrorType $
+						"createDirectoryFrom: " ++ fromRawFilePath topdir ++ " does not exist"
+			| otherwise -> createdirs $
+					map (topdir P.</>) (reverse (scanl1 (P.</>) dirs))
+		_ -> liftIO $ ioError $ customerror userErrorType
+			("createDirectoryFrom: not located in " ++ unwords (map fromRawFilePath topdirs))
   where
 	customerror t s = mkIOError t s Nothing (Just (fromRawFilePath dir0))