Shake+ Extended - Experimental Mechanisms For Shake
This library extends
shake-plus, which enriches
shake with ReaderT
and the
Path
library. This extended ruleset introduces
within, for better keeping track
of source and output directories, as well as batch loading mechanisms using
ixset-typed.
Using Within
One common complaint about Shake is having to keep track of source and output
directories and translating FilePath
s when using the input to an Action
,
leading to lots of repetition of the form (sourceFolder </>) . (-<.> ".ext") . dropDirectory1
which is prone to breakage. Using Path
helps this to some
degree, but in some cases is even more annoying because lots of Path
functions use MonadThrow
, leading to lots of monadic steps inside an
RAction
.
To alleviate this somewhat, we use Within b (Path Rel File)
as a standard
pattern for representing a file within a directory. Within
is a type
available in the within package
that is simply a newtype wrapper over an Env
comonad with the environment
specialized to Path b Dir
. We provide variants of the file operations and
rules that typically accept or return Path
s or contain callbacks that expect
paths and change these to Within
values. These functions are generally
suffixed within
. Here is the variant of getDirectoryFiles
that
produces Within
values.
getDirectoryFilesWithin' :: MonadAction m => Within Rel [FilePattern] -> m [Within b (Path Rel File)]
You can convert to and from this within-style using within
and fromWithin
.
let x = $(mkRelFile "a.txt") `within` $(mkRelDir "foo") -- Within Rel (Path Rel File)
fromWithin x -- produces a `Path Rel File`
and you can assert that an existing path lies in a directory by using asWithin
, which throws
if the directory is not a proper prefix of the Path
.
$(mkRelFile "foo/a.txt") `asWithin` $(mkRelDir "foo") -- fine
$(mkRelFile "a.txt") `asWithin` $(mkRelDir "foo") -- throws error
Filerules such as (%>)
have within-style variants that accept an (Path b Dir) FilePattern
on the left and carry that env to the callback.
(%^>) :: (Partial, MonadReader r m, MonadRules m) => Within Rel FilePattern -> (Within Rel (Path Rel File) -> RAction r ()) -> m ()
You change the underlying filepath with fmap
or mapM
, whilst you can move
to a new parent directory by using localDir
, or localDirM
which is defined
in the Within
library for when the map between parent directories may throw.
The Within
library also contains more functions and instances for more
precise changes between output and source directories.