Symlink treated as directory

[andreasabel]

This is

• Symlink treated as directory agda/fix-whitespace#9

Reproducer in filepattern-0.1.2:

$ mkdir dir
$ mkdir dir/a
$ mkdir dir/b
$ touch dir/a/file
$ ln -s dir/a/file dir/b/file
$ tree
.
└── dir
    ├── a
    │   └── file
    └── b
        └── file -> dir/a/file
$ ghci
GHCi, version 9.2.3: https://www.haskell.org/ghc/  :? for help
ghci> :m + System.FilePattern.Directory
ghci> getDirectoryFiles "." ["**"]
*** Exception: ./dir/b/file/: getDirectoryContents:openDirStream: does not exist (No such file or directory)

[andreasabel]

Relevant code:

filepattern/src/System/FilePattern/Directory.hs

Lines 94 to 101 in 1fe716c

	isFile <- whenMaybe (stepDone yes /= [] && stepDone no == []) (doesFileExist path)
	case isFile of
	Just True -> pure [parts ++ x]
	_ | StepEverything <- stepNext no -> pure []
	| StepOnly [] <- stepNext yes -> pure []
	| otherwise -> do
	b <- if doesExist && isFile == Just False then pure True else doesDirectoryExist path
	if not b then pure [] else f (parts ++ x ++ "/") yes no

In

filepattern/src/System/FilePattern/Directory.hs

Line 100 in 1fe716c

b <- if doesExist && isFile == Just False then pure True else doesDirectoryExist path

we get isFile == Just False for a symlink, which is then treated as directory.
The docs for doesFileExist are misleading (outright wrong):
https://hackage.haskell.org/package/directory-1.3.7.1/docs/System-Directory.html#v:doesFileExist

The operation doesFileExist returns True if the argument file exists and is not a directory, and False otherwise.

[andreasabel]

Since if doesExist && isFile == Just False then pure True isn't working for symlinks, we need to check doesDirectoryExist anyway, thus can get rid of the doesExist optimization altogether. Implemented in:

• Fix #5 by removing doesExist optimisation in getDirectoryFiles #6

[andreasabel]

Ping @ndmitchell.

[ndmitchell]

Thanks for the diff @andreasabel - unfortunately you've caught me as I'm travelling and otherwise unavailable. Hopefully will take a proper look at this tomorrow.

[andreasabel]

Thanks for merging! Please ping me when you release, so I can depend on the latest version.

[ndmitchell]

@andreasabel 0.1.3 now released with this fix

[andreasabel]

Thanks, published https://hackage.haskell.org/package/fix-whitespace-0.0.10.