Refactor biz.nix to dry up code

1 files changed, 42 insertions, 36 deletions

diff --git a/biz.nix b/biz.nix
index b6e59ce..6caadfd 100644
--- a/biz.nix
+++ b/biz.nix
@@ -19,25 +19,43 @@ let
     (x: builtins.elem x b) a;
 
   allDeps = import ./deps.nix;
+
+  # gather data needed for compiling by analyzing the main module
+  analyze = main: rec {
+    # path to the module relative to the git root
+    relpath = builtins.replaceStrings ["${root}/"] [""]
+        (builtins.toString main);
+    # Haskell-appropriate name of the module
+    module = builtins.replaceStrings ["/" ".hs"] ["." ""] relpath;
+    # file contents
+    content = builtins.readFile main;
+    # search for the ': exe' declaration
+    exe = builtins.head (lists.flatten (removeNull
+      (map (builtins.match "^-- : exe ([[:alnum:]._-]*)$")
+        (lines content))));
+    # collect all of the ': dep' declarations
+    deps = lists.flatten (removeNull
+      (map (builtins.match "^-- : dep ([[:alnum:]._-]*)$")
+        (lines content)));
+  };
+
+  mkGhc = compiler: (deps: compiler (hp:
+    if (subset deps allDeps)
+    then depsToPackageSet hp deps
+    else throw ''
+      missing from deps.nix:
+      ${toString (lib.lists.subtractLists allDeps deps)}
+    ''));
+
+  ghc_ = mkGhc pkgs.haskell.packages.ghc865.ghcWithHoogle;
+  ghcjs_ = mkGhc pkgs.haskell.packages.ghcjs.ghcWithPackages;
 in {
   buildGhc = main:
     let
-      relpath = builtins.replaceStrings ["${root}/"] [""] (builtins.toString main);
-      module = builtins.replaceStrings ["/" ".hs"] ["." ""] relpath;
-      content = builtins.readFile main;
-      exe = builtins.head (lists.flatten (removeNull
-        (map (builtins.match "^-- : exe ([[:alnum:]._-]*)$")
-          (lines content))));
-      deps = lists.flatten (removeNull
-        (map (builtins.match "^-- : dep ([[:alnum:]._-]*)$")
-          (lines content)));
-      ghc = pkgs.haskell.packages.ghc865.ghcWithHoogle (hp:
-          if (subset deps allDeps)
-          then depsToPackageSet hp deps
-          else throw
-            "missing from deps.nix: ${toString (lib.lists.subtractLists allDeps deps)}");
+      data = analyze main;
+      ghc = ghc_ data.deps;
     in stdenv.mkDerivation {
-      name = module;
+      name = data.module;
       src = ./.;
       nativeBuildInputs = [ ghc ];
       strictDeps = true;
@@ -46,8 +64,8 @@ in {
         # compile with ghc
         ${ghc}/bin/ghc -Werror -i. \
             --make ${main} \
-            -main-is ${module} \
-            -o $out/bin/${exe}
+            -main-is ${data.module} \
+            -o $out/bin/${data.exe}
       '';
       # the install process was handled above
       installPhase = "exit 0";
@@ -55,22 +73,10 @@ in {
 
   buildGhcjs = main:
     let
-      relpath = builtins.replaceStrings ["${root}/"] [""] (builtins.toString main);
-      module = builtins.replaceStrings ["/" ".hs"] ["." ""] relpath;
-      content = builtins.readFile main;
-      exe = builtins.head (lists.flatten (removeNull
-        (map (builtins.match "^-- : exe ([[:alnum:]._-]*)$")
-          (lines content))));
-      deps = lists.flatten (removeNull
-        (map (builtins.match "^-- : dep ([[:alnum:]._-]*)$")
-          (lines content)));
-      ghcjs = pkgs.haskell.packages.ghcjs.ghcWithPackages (hp:
-        if (subset deps allDeps)
-        then depsToPackageSet hp deps
-        else throw
-          "missing from deps.nix: ${toString (lib.lists.subtractLists allDeps deps)}");
+      data = analyze main;
+      ghcjs = ghcjs_ data.deps;
     in stdenv.mkDerivation {
-      name = module;
+      name = data.module;
       src = ./.;
       nativeBuildInputs = [ ghcjs ];
       strictDeps = true;
@@ -79,14 +85,14 @@ in {
         # compile with ghcjs
         ${ghcjs}/bin/ghcjs -Werror -i. \
             --make ${main} \
-            -main-is ${module} \
-            -o ${exe}
+            -main-is ${data.module} \
+            -o ${data.exe}
         # optimize js output
         ${pkgs.closurecompiler}/bin/closure-compiler \
-          ${exe}/all.js > $out/static/${exe}
+          ${data.exe}/all.js > $out/static/${data.exe}
       '';
       installPhase = "exit 0";
     } // { env = ghcjs; };
 
-  globalGhc = pkgs.haskell.packages.ghc865.ghcWithHoogle (hp: depsToPackageSet hp allDeps);
+  globalGhc = ghc_ allDeps;
 }