implemented createDirectoryUnder

Utility/Directory.hs

@@ -1,11 +1,12 @@
 {- directory traversal and manipulation
  -
- - Copyright 2011-2014 Joey Hess <id@joeyh.name>
+ - Copyright 2011-2020 Joey Hess <id@joeyh.name>
  -
  - License: BSD-2-clause
  -}
 
 {-# LANGUAGE CPP #-}
+{-# LANGUAGE LambdaCase #-}
 {-# OPTIONS_GHC -fno-warn-tabs #-}
 
 module Utility.Directory (
@@ -19,6 +20,7 @@ import System.FilePath
 import System.PosixCompat.Files
 import Control.Applicative
 import System.IO.Unsafe (unsafeInterleaveIO)
+import System.IO.Error
 import Data.Maybe
 import Prelude
 
@@ -28,10 +30,12 @@ import Control.Monad.IfElse
 #endif
 
 import Utility.SystemDirectory
+import Utility.Path
 import Utility.Tmp
 import Utility.Exception
 import Utility.Monad
 import Utility.Applicative
+import Utility.PartialPrelude
 
 dirCruft :: FilePath -> Bool
 dirCruft "." = True
@@ -154,3 +158,65 @@ nukeFile file = void $ tryWhenExists go
 #else
 	go = removeFile file
 #endif
+
+{- Like createDirectoryIfMissing True, but it will only create
+ - missing parent directories up to but not including the directory
+ - in the first parameter.
+ -
+ - 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.
+ -
+ - The exception thrown is the same that createDirectory throws if the
+ - parent directory does not exist.
+ -
+ - If the second FilePath is not under the first
+ - 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.
+ - 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.
+ -}
+createDirectoryUnder :: FilePath -> FilePath -> IO ()
+createDirectoryUnder topdir dir0 = do
+	p <- relPathDirToFile topdir dir0
+	let dirs = splitDirectories p
+	-- Catch cases where the dir is not beneath the 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 ".." || isAbsolute p
+		then ioError $ customerror userErrorType
+			("createDirectoryFrom: not located in " ++ 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 unlessM (doesDirectoryExist topdir) $
+				ioError $ customerror doesNotExistErrorType
+					"createDirectoryFrom: does not exist"
+			else createdirs $
+				map (topdir </>) (reverse (scanl1 (</>) dirs))
+  where
+	customerror t s = mkIOError t s Nothing (Just dir0)
+
+	createdirs [] = pure ()
+	createdirs (dir:[]) = createdir dir ioError
+	createdirs (dir:dirs) = createdir dir $ \_ -> do
+		createdirs dirs
+		createdir dir ioError
+
+	-- This is the same method used by createDirectoryIfMissing,
+	-- in particular the handling of errors that occur when the
+	-- directory already exists. See its source for explanation
+	-- of several subtleties.
+	createdir dir notexisthandler = tryIOError (createDirectory dir) >>= \case
+		Right () -> pure ()
+		Left e
+			| isDoesNotExistError e -> notexisthandler e
+			| isAlreadyExistsError e || isPermissionError e -> do
+				unlessM (doesDirectoryExist dir) $
+					ioError e
+			| otherwise -> ioError e