herringbone-0.1.1: A library for compiling and serving static web assets.

Safe HaskellNone




herringbone is a Haskell library for compiling and serving web assets. It aims to make it dead simple to create a Middleware or Application which deals with all of your static assets, including preprocessing for languages like Fay, CoffeeScript, Sass, and LESS.

It takes most of its inspiration from the Ruby library, Sprockets, hence the name.


 import Web.Herringbone

 fay, sass :: PP

 hb = Herringbone
 hb = herringbone
     ( addSourceDir "assets"
     . setDestDir   "compiled_assets"
     . addPreprocessors [fay, sass]

 -- You can now access assets programmatically
 asset <- findAsset hb (fromJust . makeLogicalPath $ ["application.js"])

 -- Or serve them with a Wai application
 app = toApplication hb


Creating a Herringbone

data Herringbone Source

The 'main' datatype in this library. All of the important functions will take a Herringbone as their first argument.

hbSourceDir :: Herringbone -> FilePathSource

The directory where Herringbone will look when searching for assets.

hbDestDir :: Herringbone -> FilePathSource

The directory to place assets in after compilation.

hbPPs :: Herringbone -> PPsSource

The collection of preprocessors that will be used when preprocessing assets.

hbVerbose :: Herringbone -> BoolSource

True iff the Herringbone has the verbose setting enabled.

data HerringboneSettings Source

Contains configuration.




settingsSourceDir :: FilePath

The directory to take asset sources from.

settingsDestDir :: FilePath

Where to copy assets to after they've been compiled.

settingsPPs :: PPs


settingsVerbose :: Bool

Dump debugging data to stdout on every request.


data LogicalPath Source

All assets in Herringbone are referenced by their logical path. This is the path to an asset, relative to the source directory.

makeLogicalPath :: [Text] -> Maybe LogicalPathSource

Create a LogicalPath from a list of path segments. For example, ["data", "dogs.txt"] would map to data/dogs.txt (relative to the source directory). This returns Nothing if the path would be unsafe (that is, if it contains ".."), to prevent directory traversal attacks.

unsafeMakeLogicalPath :: [Text] -> LogicalPathSource

Create a LogicalPath without checking any of the values.

data Asset Source

A preprocessed asset. Any function that returns this will already have done the preprocessing (if necessary).




assetSize :: Integer

Size of the asset in bytes.

assetSourcePath :: FilePath

Path to the asset's source file on disk.

assetFilePath :: FilePath

Path to the preprocessed asset on disk. Note that assets which do not require preprocessing will still be copied to the destination directory.

assetModifiedTime :: UTCTime

Modification time of the asset's source file.


findAsset :: Herringbone -> LogicalPath -> IO (Either AssetError Asset)Source

The most important function in this library. Attempts to find the asset referenced by the given LogicalPath, compiles it if necessary (based on file modification time), and returns it to you as an Asset (or an AssetError, if something went wrong).

precompile :: Herringbone -> IO [(LogicalPath, AssetError)]Source

Precompiles all assets, returning a list of the logical paths of assets that failed to compile (if any) together with AssetError values describing what went wrong.


data PP Source

A preprocessor something which is run on the asset before it is served. Preprocessors are run when a file matches its rule. For example, if you have a preprocessor which takes "coffee" files and emits "js" files, there is a file named "application.coffee", and you request "application.js", Herringbone will run the coffee preprocessor on "application.coffee" and serve you the result.




ppName :: Text

Identifies a preprocessor. Mainly useful for debugging compile errors.

ppConsumes :: Text

Extension for files this preprocessor consumes.

ppProduces :: Text

Extension for files this preprocessor produces.

ppAction :: PPAction

Performs the compilation.


data PPs Source

A collection of preprocessors. This can store many preprocessors which produce files with the same extension, but may not store more than one preprocessor which consumes files of a particular extension.


data AssetError Source

A value describing an error that occurred while trying to produce an Asset.

type CompileError = ByteStringSource

A string which should contain information about why an asset failed to compile.

data PPReader Source

Data which is given to preprocessors on the off-chance that they need it (eg, Fay)




ppReaderHb :: Herringbone

The Herringbone which was used to build the asset

ppReaderSourcePath :: FilePath

The file path to the source file

ppReaderPPs :: [PP]

Preprocessors being invoked. Currently this will only ever have zero or one elements; in the future, Herringbone may be able to run multiple preprocessors on a single file.

data PPM a Source

A monad in which preprocessor actions happen.