[SOLVED] In Haskell Shake, how can I want a file pattern?

In Haskell Shake, how can I want a file pattern?

I have a directory of xml files in a source directory that I want to turn into a directory of html files in a destination directory. It seems I can use getDirectoryFiles to get files from a directory, but that is an Action, and want needs not an Action [FilePath] but just a [FilePath]. How can I do something like want ["dest/*.html"] in Shake?

Solution

If I understand you correctly, you can do like this.

First of all, write a rule that creates the html file from xml.

main = shakeArgs shakeOptions $ do
    "dest/*.html" %> \out -> do
        let src = "source" </> dropDirectory1 out -<.> "xml"
        -- todo: generate out (HTML) from src (XML)

Then you can write a rule by action that will be run in every build execution.

main = shakeArgs shakeOptions $ do
    action $ do
        srcs <- getDirectoryFiles "source" ["*.xml"]
        need ["dest" </> src -<.> "html" | src <- srcs]

    "dest/*.html" %> \out -> do
        let src = "source" </> dropDirectory1 out -<.> "xml"
        -- todo: translate HTML(out) from XML(src)

For your information, want defined like: want xs = action $ need xs.