Factor out nix builder into Haskell.nix

This also fixed a bug where every dependency would get pulled into the Haskell
target while searching for transitive dependencies.

2 files changed, 41 insertions, 1 deletions

diff --git a/Biz/Bild/Example.hs b/Biz/Bild/Example.hs
index f812707..87472bb 100644
--- a/Biz/Bild/Example.hs
+++ b/Biz/Bild/Example.hs
@@ -1,5 +1,9 @@
+{-# LANGUAGE NoImplicitPrelude #-}
+
 -- : out example
 module Biz.Bild.Example where
 
+import Alpha
+
 main :: IO ()
-main = print "hi"
+main = putStrLn "Hello world"
diff --git a/Biz/Bild/Haskell.nix b/Biz/Bild/Haskell.nix
new file mode 100644
index 0000000..24b6686
--- /dev/null
+++ b/Biz/Bild/Haskell.nix
@@ -0,0 +1,36 @@
+{ srcs # list of files
+, root # path to git root
+, packageSet # name mapped to private.${packageSet}, e.g. 'ghcWith'
+, langDeps ? null # list of deps (as a string), split and passed to packageSet
+, name # exe name
+, main # entrypoint file
+, mainIs # entrypoint module name
+}:
+with import (/. + root + "/Biz/Bild.nix") {};
+with builtins;
+let
+  srcs_ = lib.strings.splitString " " srcs;
+  skip = ["_" ".direnv"];
+  filter = file: type:
+    if elem (baseNameOf file) skip then false
+    # TODO: this means any new directory will cause a rebuild. this bad.
+    # i should recurse into the directory and match against the srcsr
+    else if type == "directory" then true
+    else if type == "regular" then builtins.elem file srcs_
+    else false;
+   deps = pkgset:
+     if langDeps != null then
+       private.selectAttrs (lib.strings.splitString " " langDeps) pkgset
+     else
+       [];
+in stdenv.mkDerivation {
+  inherit name;
+  buildInputs = [ (private.${packageSet} deps) ];
+  src = lib.sources.cleanSourceWith {inherit filter; src = lib.sources.cleanSource root;};
+  buildPhase = ''
+    ghc -Werror -i$src -odir. -hidir. --make $src/${main} -main-is "${mainIs}" -o ${name}
+  '';
+  installPhase = ''
+    mkdir -p $out/bin && cp ${name} $out/bin
+  '';
+}