Fix inappropriate type (Not a directory) error

In Linux module for File paths in recursive mode.

src/Streamly/Internal/FileSystem/Event/Linux.hs

@@ -193,6 +193,7 @@ import qualified Streamly.Internal.Data.Fold as FL
 import qualified Streamly.Internal.Data.Parser as PR
 import qualified Streamly.Internal.Data.Stream.IsStream as S
 import qualified Streamly.Internal.FileSystem.Dir as Dir
+import qualified System.Directory as Dir
 import qualified Streamly.Internal.FileSystem.Handle as FH
 import qualified Streamly.Internal.Unicode.Stream as U
 
@@ -745,7 +746,8 @@ addToWatch cfg@Config{..} watch0@(Watch handle wdMap) root0 path0 = do
     --
     -- XXX toDirs currently uses paths as String, we need to convert it
     -- to "/" separated by byte arrays.
-    when watchRec $ do
+    pathIsDir <- Dir.doesDirectoryExist $ utf8ToString absPath
+    when (watchRec && pathIsDir) $ do
         S.mapM_ (\p -> addToWatch cfg watch0 root (appendPaths path p))
             $ S.mapM toUtf8
             $ Dir.toDirs $ utf8ToString absPath

src/Streamly/Internal/FileSystem/Event/Windows.hs

@@ -12,13 +12,13 @@
 --
 -- =Overview
 --
--- Use 'watchTrees'or 'watchPaths' with a list of file system paths you want to
--- watch as argument. It returns a stream of 'Event' representing the file
--- system events occurring under the watched paths.
+-- Use 'watchRecursive'or 'watch' with a list of file system dir paths you
+-- want to watch as argument. It returns a stream of 'Event' representing the
+-- file system events occurring under the watched paths.
 --
 -- @
 -- {-\# LANGUAGE MagicHash #-}
--- Stream.mapM_ (putStrLn . 'showEvent') $ 'watchTrees' [Array.fromCString\# "path"#]
+-- Stream.mapM_ (putStrLn . 'showEvent') $ 'watchRecursive' [Array.fromCString\# "path"#]
 -- @
 --
 -- 'Event' is an opaque type. Accessor functions (e.g. 'showEvent' above)

test/Streamly/Test/FileSystem/Event/Linux.hs

@@ -149,4 +149,4 @@ main = do
     runRec SymLinkOrigPath recSymTests
     -- XXX This fails with exceptions, ideally it should work the same as in
     -- non-recursive mode
-    -- runRec FileType fileRootTests
+    runRec FileType fileRootTests

test/Streamly/Test/FileSystem/Event/Windows.hs

@@ -38,6 +38,7 @@ main = do
     -- TODO create/modify/delete/move with root path as a regular file, copy
     -- from macOS tests
     -- run FileType fileRootTests
+    -- Windows watch events only supports dir path as root.
 
     let recTests =
             [ dirCreateWithParent "subdir\\dir"