Path

This library provides a well-typed representation of paths in a filesystem directory tree. A path is represented by a number of path components separated by a path separator which is a / on POSIX systems and can be a / or \ on Windows.

The root of the tree is represented by a / on POSIX and a drive letter followed by a / or \ on Windows (e.g. C:\). Paths can be absolute or relative. An absolute path always starts from the root of the tree (e.g. /x/y) whereas a relative path never starts with the root (e.g. x/y). Just like we represent the notion of an absolute root by "/", the same way we represent the notion of a relative root by ".". The relative root denotes the directory which contains the first component of a relative path.

Types

data Path b t

Path of some base and type.

The type variables are:

• b — base, the base location of the path; absolute or relative.
• t — type, whether file or directory.

Internally is a string. The string can be of two formats only:

1. File format: file.txt, foo/bar.txt, /foo/bar.txt
2. Directory format: foo/, /foo/bar/

All directories end in a trailing separator. There are no duplicate path separators //, no .., no ./, no ~/, etc.

Instances

Eq (Path b t)

String equality.

The following property holds:

show x == show y ≡ x == y

Methods

(==) :: Path b t -> Path b t -> Bool

(/=) :: Path b t -> Path b t -> Bool

Ord (Path b t)

String ordering.

The following property holds:

show x `compare` show y ≡ x `compare` y

Methods

compare :: Path b t -> Path b t -> Ordering

(<) :: Path b t -> Path b t -> Bool

(<=) :: Path b t -> Path b t -> Bool

(>) :: Path b t -> Path b t -> Bool

(>=) :: Path b t -> Path b t -> Bool

max :: Path b t -> Path b t -> Path b t

min :: Path b t -> Path b t -> Path b t

Show (Path b t)

Same as 'show . Path.toFilePath'.

The following property holds:

x == y ≡ show x == show y

Methods

showsPrec :: Int -> Path b t -> ShowS

show :: Path b t -> String

showList :: [Path b t] -> ShowS

Hashable (Path b t)

Methods

hashWithSalt :: Int -> Path b t -> Int

hash :: Path b t -> Int

ToJSON (Path b t)

Methods

toJSON :: Path b t -> Value

toEncoding :: Path b t -> Encoding

toJSONList :: [Path b t] -> Value

toEncodingList :: [Path b t] -> Encoding

FromJSON (Path Rel Dir)

Methods

parseJSON :: Value -> Parser (Path Rel Dir)

parseJSONList :: Value -> Parser [Path Rel Dir]

FromJSON (Path Rel File)

Methods

parseJSON :: Value -> Parser (Path Rel File)

parseJSONList :: Value -> Parser [Path Rel File]

FromJSON (Path Abs Dir)

Methods

parseJSON :: Value -> Parser (Path Abs Dir)

parseJSONList :: Value -> Parser [Path Abs Dir]

FromJSON (Path Abs File)

Methods

parseJSON :: Value -> Parser (Path Abs File)

parseJSONList :: Value -> Parser [Path Abs File]

NFData (Path b t)

Methods

rnf :: Path b t -> ()

data Abs

An absolute path.

Instances

FromJSON (Path Abs Dir)

Methods

parseJSON :: Value -> Parser (Path Abs Dir)

parseJSONList :: Value -> Parser [Path Abs Dir]

FromJSON (Path Abs File)

Methods

parseJSON :: Value -> Parser (Path Abs File)

parseJSONList :: Value -> Parser [Path Abs File]

data Rel

A relative path; one without a root. Note that a .. path component to represent the parent directory is not allowed by this library.

Instances

FromJSON (Path Rel Dir)

Methods

parseJSON :: Value -> Parser (Path Rel Dir)

parseJSONList :: Value -> Parser [Path Rel Dir]

FromJSON (Path Rel File)

Methods

parseJSON :: Value -> Parser (Path Rel File)

parseJSONList :: Value -> Parser [Path Rel File]

data File

A file path.

Instances

FromJSON (Path Rel File)

Methods

parseJSON :: Value -> Parser (Path Rel File)

parseJSONList :: Value -> Parser [Path Rel File]

FromJSON (Path Abs File)

Methods

parseJSON :: Value -> Parser (Path Abs File)

parseJSONList :: Value -> Parser [Path Abs File]

data Dir

A directory path.

Instances

FromJSON (Path Rel Dir)

Methods

parseJSON :: Value -> Parser (Path Rel Dir)

parseJSONList :: Value -> Parser [Path Rel Dir]

FromJSON (Path Abs Dir)

Methods

parseJSON :: Value -> Parser (Path Abs Dir)

parseJSONList :: Value -> Parser [Path Abs Dir]

Exceptions

data PathException

Exceptions that can occur during path operations.

Since: 0.6.0

Constructors

InvalidAbsDir FilePath

InvalidRelDir FilePath

InvalidAbsFile FilePath

InvalidRelFile FilePath

NotAProperPrefix FilePath FilePath

Instances

Eq PathException

Methods

(==) :: PathException -> PathException -> Bool

(/=) :: PathException -> PathException -> Bool

Show PathException

Methods

showsPrec :: Int -> PathException -> ShowS

show :: PathException -> String

showList :: [PathException] -> ShowS

Exception PathException

Methods

toException :: PathException -> SomeException

fromException :: SomeException -> Maybe PathException

displayException :: PathException -> String

QuasiQuoters

Using the following requires the QuasiQuotes language extension.

For Windows users, the QuasiQuoters are especially beneficial because they prevent Haskell from treating \ as an escape character. This makes Windows paths easier to write.

[absfile|C:\chris\foo.txt|]

absdir :: QuasiQuoter

Construct a Path Abs Dir using QuasiQuotes.

[absdir|/|]

[absdir|/home/chris|]

Remember: due to the nature of absolute paths a path like [absdir|/home/chris|] may compile on your platform, but it may not compile on another platform (Windows).

Since: 0.5.13

reldir :: QuasiQuoter

Construct a Path Rel Dir using QuasiQuotes.

[absdir|/home|]</>[reldir|chris|]

Since: 0.5.13

absfile :: QuasiQuoter

Construct a Path Abs File using QuasiQuotes.

[absfile|/home/chris/foo.txt|]

Remember: due to the nature of absolute paths a path like [absdir|/home/chris/foo.txt|] may compile on your platform, but it may not compile on another platform (Windows).

Since: 0.5.13

relfile :: QuasiQuoter

Construct a Path Rel File using QuasiQuotes.

[absdir|/home/chris|]</>[relfile|foo.txt|]

Since: 0.5.13

Operations

(</>) :: Path b Dir -> Path Rel t -> Path b t infixr 5

Append two paths.

The following cases are valid and the equalities hold:

$(mkAbsDir x) </> $(mkRelDir y) = $(mkAbsDir (x ++ "/" ++ y))

$(mkAbsDir x) </> $(mkRelFile y) = $(mkAbsFile (x ++ "/" ++ y))

$(mkRelDir x) </> $(mkRelDir y) = $(mkRelDir (x ++ "/" ++ y))

$(mkRelDir x) </> $(mkRelFile y) = $(mkRelFile (x ++ "/" ++ y))

The following are proven not possible to express:

$(mkAbsFile …) </> x

$(mkRelFile …) </> x

x </> $(mkAbsFile …)

x </> $(mkAbsDir …)

stripProperPrefix :: MonadThrow m => Path b Dir -> Path b t -> m (Path Rel t)

If the directory in the first argument is a proper prefix of the path in the second argument strip it from the second argument, generating a path relative to the directory. Throws NotAProperPrefix if the directory is not a proper prefix of the path.

The following properties hold:

stripProperPrefix x (x </> y) = y

Cases which are proven not possible:

stripProperPrefix (a :: Path Abs …) (b :: Path Rel …)

stripProperPrefix (a :: Path Rel …) (b :: Path Abs …)

In other words the bases must match.

Since: 0.6.0

isProperPrefixOf :: Path b Dir -> Path b t -> Bool

Determines if the path in the first parameter is a proper prefix of the path in the second parameter.

The following properties hold:

not (x `isProperPrefixOf` x)

x `isProperPrefixOf` (x </> y)

Since: 0.6.0

parent :: Path b t -> Path b Dir

Take the parent path component from a path.

The following properties hold:

parent (x </> y) == x
parent "/x" == "/"
parent "x" == "."

On the root (absolute or relative), getting the parent is idempotent:

parent "/" = "/"
parent "." = "."

filename :: Path b File -> Path Rel File

Extract the file part of a path.

The following properties hold:

filename (p </> a) == filename a

dirname :: Path b Dir -> Path Rel Dir

Extract the last directory name of a path.

The following properties hold:

dirname $(mkRelDir ".") == $(mkRelDir ".")

dirname (p </> a) == dirname a

fileExtension :: Path b File -> String

Get extension from given file path.

Since: 0.5.11

addFileExtension

Arguments

:: MonadThrow m

=> String

Extension to add

-> Path b File

Old file name

-> m (Path b File)

New file name with the desired extension added at the end

Add extension to given file path. Throws if the resulting filename does not parse.

>>> addFileExtension "txt $(mkRelFile "foo")
"foo.txt"
>>> addFileExtension "symbols" $(mkRelFile "Data.List")
"Data.List.symbols"
>>> addFileExtension ".symbols" $(mkRelFile "Data.List")
"Data.List.symbols"
>>> addFileExtension "symbols" $(mkRelFile "Data.List.")
"Data.List..symbols"
>>> addFileExtension ".symbols" $(mkRelFile "Data.List.")
"Data.List..symbols"
>>> addFileExtension "evil/" $(mkRelFile "Data.List")
*** Exception: InvalidRelFile "Data.List.evil/"

Since: 0.6.1

(<.>) infixr 7

Arguments

:: MonadThrow m

=> Path b File

Old file name

-> String

Extension to add

-> m (Path b File)

New file name with the desired extension added at the end

A synonym for addFileExtension in the form of an operator. See more examples there.

>>> $(mkRelFile "Data.List") <.> "symbols"
"Data.List.symbols"
>>> $(mkRelFile "Data.List") <.> "evil/"
*** Exception: InvalidRelFile "Data.List.evil/"

Since: 0.6.1

setFileExtension

Arguments

:: MonadThrow m

=> String

Extension to set

-> Path b File

Old file name

-> m (Path b File)

New file name with the desired extension

Replace/add extension to given file path. Throws if the resulting filename does not parse.

Since: 0.5.11

(-<.>) infixr 7

Arguments

:: MonadThrow m

=> Path b File

Old file name

-> String

Extension to set

-> m (Path b File)

New file name with the desired extension

A synonym for setFileExtension in the form of an operator.

Since: 0.6.0

Parsing

parseAbsDir :: MonadThrow m => FilePath -> m (Path Abs Dir)

Convert an absolute FilePath to a normalized absolute dir Path.

Throws: InvalidAbsDir when the supplied path:

• is not an absolute path
• contains a .. path component representing the parent directory
• is not a valid path (See isValid)

parseRelDir :: MonadThrow m => FilePath -> m (Path Rel Dir)

Convert a relative FilePath to a normalized relative dir Path.

Throws: InvalidRelDir when the supplied path:

• is not a relative path
• is ""
• contains a .. path component representing the parent directory
• is not a valid path (See isValid)

parseAbsFile :: MonadThrow m => FilePath -> m (Path Abs File)

Convert an absolute FilePath to a normalized absolute file Path.

Throws: InvalidAbsFile when the supplied path:

• is not an absolute path

• is a directory path i.e.

  • has a trailing path separator
  • is . or ends in /.
• contains a .. path component representing the parent directory
• is not a valid path (See isValid)

parseRelFile :: MonadThrow m => FilePath -> m (Path Rel File)

Convert a relative FilePath to a normalized relative file Path.

Throws: InvalidRelFile when the supplied path:

• is not a relative path
• is ""

• is a directory path i.e.

  • has a trailing path separator
  • is . or ends in /.
• contains a .. path component representing the parent directory
• is not a valid path (See isValid)

Conversion

toFilePath :: Path b t -> FilePath

Convert to a FilePath type.

All directories have a trailing slash, so if you want no trailing slash, you can use dropTrailingPathSeparator from the filepath package.

fromAbsDir :: Path Abs Dir -> FilePath

Convert absolute path to directory to FilePath type.

fromRelDir :: Path Rel Dir -> FilePath

Convert relative path to directory to FilePath type.

fromAbsFile :: Path Abs File -> FilePath

Convert absolute path to file to FilePath type.

fromRelFile :: Path Rel File -> FilePath

Convert relative path to file to FilePath type.

TemplateHaskell constructors

These require the TemplateHaskell language extension.

mkAbsDir :: FilePath -> Q Exp

Make a Path Abs Dir'.

Remember: due to the nature of absolute paths this (e.g. /home/foo) may compile on your platform, but it may not compile on another platform (Windows).

mkRelDir :: FilePath -> Q Exp

Make a Path Rel Dir.

mkAbsFile :: FilePath -> Q Exp

Make a Path Abs File.

Remember: due to the nature of absolute paths this (e.g. /home/foo) may compile on your platform, but it may not compile on another platform (Windows).

mkRelFile :: FilePath -> Q Exp

Make a Path Rel File.

Deprecated

type PathParseException = PathException

Deprecated: Please use PathException instead.

Same as PathException.

stripDir :: MonadThrow m => Path b Dir -> Path b t -> m (Path Rel t)

Deprecated: Please use stripProperPrefix instead.

Same as stripProperPrefix.

isParentOf :: Path b Dir -> Path b t -> Bool

Deprecated: Please use isProperPrefixOf instead.

Same as isProperPrefixOf.