Making Cabal Aware of External TemplateHaskell Dependencies

Question

To embed some static files in a build, I'm using: https://hackage.haskell.org/package/file-embed-0.0.10.1/docs/Data-FileEmbed.html

It allows you to do:

MyFile.hs

myFile :: Data.ByteString.ByteString
myFile = $(embedFile "something/external.txt")

To embed files into the produced binary.

However, one irksome thing is that cabal doesn't know that a file using embedFile depends on the file it loads (and therefore changes to something/external.txt don't cause MyFile to be re-built on build).

Is there any way to tell cabal about this dependency? The only solution I have now is to just touch the Haskell file to cause it to be recompiled, but this is tedious.

see https://www.haskell.org/cabal/users-guide/developing-packages.html#pkg-field-data-files — Regis Kuckaertz, Apr 10 '18 at 15:20

score 2 · Accepted Answer · answered Apr 10 '18 at 15:16

2

addDependentFile is part of template Haskell. It tells ghc to use that file in dependency calculations - cabal isn't even needed.

embedFile should be calling that. The fact that it isn't makes me suspicious about the library. Still, you can create a helper that looks something like this:

embed :: FilePath -> Q Exp
embed p = addDependentFile p >> embedFile p

Just mind TH's staging restrictions, and put that in a file that doesn't use it.

answered Apr 10 '18 at 15:16

Carl

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Yep, that's exactly what I was looking for. That's so smart that they thought ahead to include that! Thank you so much! – Bailey Parker Apr 10 '18 at 15:55
1

Doesn’t seem to work for me under Cabal 3.2. People on IRC say that Cabal is not aware of `addDependentFile`. – Vasiliy Faronov Apr 14 '21 at 14:54

Making Cabal Aware of External TemplateHaskell Dependencies

1 Answers1