Data.FileEmbed

This module uses template Haskell. Following is a simplified explanation of usage for those unfamiliar with calling Template Haskell functions.

The function embedFile in this modules embeds a file into the executable that you can use it at runtime. A file is represented as a ByteString. However, as you can see below, the type signature indicates a value of type Q Exp will be returned. In order to convert this into a ByteString, you must use Template Haskell syntax, e.g.:

$(embedFile "myfile.txt")

This expression will have type ByteString. Be certain to enable the TemplateHaskell language extension, usually by adding the following to the top of your module:

{-# LANGUAGE TemplateHaskell #-}

Embed at compile time

embedFile :: FilePath -> Q Exp

Embed a single file in your source code.

import Data.String

myFile :: IsString a => a
myFile = $(embedFile "dirName/fileName")

embedOneFileOf :: [FilePath] -> Q Exp

Embed a single existing string file in your source code out of list a list of paths supplied.

embedDir :: FilePath -> Q Exp

Embed a directory recursively in your source code.

import Data.String

myDir :: IsString a => [(FilePath, a)]
myDir = $(embedDir "dirName")

Relative path manipulation

makeRelativeToProject :: FilePath -> Q FilePath

Take a relative file path and attach it to the root of the current project.

The idea here is that, when building with Stack, the build will always be executed with a current working directory of the root of the project (where your .cabal file is located). However, if you load up multiple projects with stack ghci, the working directory may be something else entirely.

This function looks at the source location of the Haskell file calling it, finds the first parent directory with a .cabal file, and uses that as the root directory for fixing the relative path.

$(makeRelativeToProject "data/foo.txt" >>= embedFile)

Since: 0.0.10