Add a builder for Agda packages.

pkgs/build-support/agda/default.nix

@@ -0,0 +1,95 @@
+# Builder for Agda packages. Mostly inspired by the cabal builder.
+#
+# Contact: stdenv.lib.maintainers.fuuzetsu
+
+{ stdenv, Agda, glibcLocales
+, writeScriptBin
+, extension ? (self: super: {})
+}:
+
+let
+  optionalString = stdenv.lib.optionalString;
+  filter = stdenv.lib.filter;
+  concatMapStringsSep = stdenv.lib.strings.concatMapStringsSep;
+  concatMapStrings = stdenv.lib.strings.concatMapStrings;
+  unwords = stdenv.lib.strings.concatStringsSep " ";
+  mapInside = xs: unwords (map (x: x + "/*") xs);
+in
+{ mkDerivation = args:
+    let
+      postprocess = x: x // {
+        sourceDirectories = filter (y: !(y == null)) x.sourceDirectories;
+        propagatedBuildInputs = filter (y : ! (y == null)) x.propagatedBuildInputs;
+        propagatedUserEnvPkgs = filter (y : ! (y == null)) x.propagatedUserEnvPkgs;
+        extraBuildFlags = filter (y : ! (y == null)) x.extraBuildFlags;
+        everythingFile = if x.everythingFile == "" then "Everything.agda" else x.everythingFile;
+      };
+
+      defaults = self : {
+        # There is no Hackage for Agda so we require src.
+        inherit (self) src name;
+
+        buildInputs = [ Agda ] ++ self.buildDepends;
+        buildDepends = [];
+        # Not much choice here ;)
+        LANG = "en_US.UTF-8";
+        LOCALE_ARCHIVE = optionalString stdenv.isLinux "${glibcLocales}/lib/locale/locale-archive";
+
+        everythingFile = "Everything.agda";
+
+        propagatedBuildInputs = self.buildDepends ++ self.buildTools;
+        propagatedUserEnvPkgs = self.buildDepends;
+
+        # Immediate source directories under which modules can be found.
+        sourceDirectories = [ ];
+
+        # This is used if we have a top-level element that only serves
+        # as the container for the source and we only care about its
+        # contents. The directories put here will have their
+        # *contents* copied over as opposed to sourceDirectories which
+        # would make a direct copy of the whole thing.
+        topSourceDirectories = [ "src" ];
+
+        buildTools = [];
+
+        # Extra stuff to pass to the Agda binary.
+        extraBuildFlags = [ "-i ." ];
+        buildFlags = let r = map (x: "-i " + x + "/share/agda") self.buildDepends;
+                         d = map (x : "-i " + x) (self.sourceDirectories ++ self.topSourceDirectories);
+                     in unwords (r ++ d ++ self.extraBuildFlags);
+
+        # We expose this as a mere convenience for any tools.
+        AGDA_PACKAGE_PATH = concatMapStrings (x: x + ":") self.buildDepends;
+
+        # Makes a wrapper available to the user. Very useful in
+        # nix-shell where all dependencies are -i'd.
+        agdaWrapper = writeScriptBin "agda" ''
+          ${Agda}/bin/agda ${self.buildFlags} "$@"
+        '';
+
+        # configurePhase is idempotent
+        configurePhase = ''
+          eval "$preConfigure"
+          export AGDA_PACKAGE_PATH=${self.AGDA_PACKAGE_PATH};
+          export PATH="${self.agdaWrapper}/bin:$PATH"
+          eval "$postConfigure"
+        '';
+
+        buildPhase = ''
+          eval "$preBuild"
+          ${Agda}/bin/agda ${self.buildFlags} ${self.everythingFile}
+          eval "$postBuild"
+        '';
+
+        installPhase = ''
+          eval "$preInstall"
+          mkdir -p $out/share/agda
+          cp -pR ${unwords self.sourceDirectories} ${mapInside self.topSourceDirectories} $out/share/agda
+          eval "$postInstall"
+        '';
+      };
+    in stdenv.mkDerivation
+         (postprocess (let super = defaults self // args self;
+                           self  = super // extension self super;
+                       in self));
+}

pkgs/top-level/all-packages.nix

@@ -6526,6 +6526,14 @@ let
 
   zziplib = callPackage ../development/libraries/zziplib { };
 
+  ### DEVELOPMENT / LIBRARIES / AGDA
+
+  agda = callPackage ../build-support/agda {
+    glibcLocales = if pkgs.stdenv.isLinux then pkgs.glibcLocales else null;
+    extension = self : super : {};
+    Agda = haskellPackages.Agda;
+    inherit writeScriptBin;
+  };
 
   ### DEVELOPMENT / LIBRARIES / JAVA