Added nix files (idris-lang#855)

.github/workflows/ci-nix.yml

@@ -0,0 +1,23 @@
+name: Nix
+on:
+  push:
+    branches:
+      - '*'
+    tags:
+      - '*'
+  pull_request:
+    branches:
+      - master
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+      with:
+          fetch-depth: 0
+    - uses: cachix/install-nix-action@v12
+      with:
+        install_url: https://github.com/numtide/nix-flakes-installer/releases/download/nix-3.0pre20200820_4d77513/install
+        extra_nix_config: |
+          experimental-features = nix-command flakes
+    - run: nix build

INSTALL.md

@@ -120,3 +120,9 @@ If you are a [nix](https://nixos.org/features.html) user you can install Idris 2
 by running the following command:
 
     nix-env -i idris2
+
+### Install from nix flakes
+
+If you are a [nix flakes](https://nixos.wiki/wiki/Flakes) user you can install Idris 2 together with all the requirements by running the following command:
+
+    nix profile install github:idris-lang/Idris2

README.md

@@ -7,6 +7,7 @@ Idris 2
 [![](https://github.com/idris-lang/Idris2/workflows/Ubuntu%20Racket/badge.svg)](https://github.com/idris-lang/Idris2/actions?query=workflow%3A"Ubuntu+Racket")
 [![](https://github.com/idris-lang/Idris2/workflows/macOS/badge.svg)](https://github.com/idris-lang/Idris2/actions?query=workflow%3A"macOS")
 [![](https://github.com/idris-lang/Idris2/workflows/API/badge.svg)](https://github.com/idris-lang/Idris2/actions?query=workflow%3A"API")
+[![](https://github.com/idris-lang/Idris2/workflows/Nix/badge.svg)](https://github.com/idris-lang/Idris2/actions?query=workflow%3A"Nix")
 
 [Idris 2](https://idris-lang.org/) is a purely functional programming language
 with first class types.

default.nix

@@ -0,0 +1,3 @@
+{ nixpkgs ? import <nixos> {} }: with nixpkgs;
+
+callPackage ./package.nix {}

flake.nix

@@ -0,0 +1,11 @@
+{
+  description = "Idris2 flake";
+
+  outputs = { self, nixpkgs }: {
+
+    packages.x86_64-linux.idris2 = import ./default.nix { nixpkgs = nixpkgs.legacyPackages.x86_64-linux; };
+
+    defaultPackage.x86_64-linux = self.packages.x86_64-linux.idris2;
+
+  };
+}

package.nix

@@ -0,0 +1,63 @@
+{ stdenv, fetchFromGitHub, makeWrapper
+, clang, chez
+}:
+
+# Uses scheme to bootstrap the build of idris2
+stdenv.mkDerivation rec {
+  pname = "idris2";
+  version = "0.3.0";
+
+  src = ./.;
+
+  strictDeps = true;
+  nativeBuildInputs = [ makeWrapper clang chez ];
+  buildInputs = [ chez ];
+
+  prePatch = ''
+    patchShebangs --build tests
+  '';
+
+  makeFlags = [ "PREFIX=$(out)" ]
+    ++ stdenv.lib.optional stdenv.isDarwin "OS=";
+
+  # The name of the main executable of pkgs.chez is `scheme`
+  buildFlags = [ "bootstrap-build" "SCHEME=scheme" ];
+
+  checkTarget = "bootstrap-test";
+
+  # TODO: Move this into its own derivation, such that this can be changed
+  #       without having to recompile idris2 every time.
+  postInstall = let
+    includedLibs = [ "base" "contrib" "network" "prelude" ];
+    name = "${pname}-${version}";
+    packagePaths = builtins.map (l: "$out/${name}/" + l) includedLibs;
+    additionalIdris2Paths = builtins.concatStringsSep ":" packagePaths;
+  in ''
+    # Remove existing idris2 wrapper that sets incorrect LD_LIBRARY_PATH
+    rm $out/bin/idris2
+    # Move actual idris2 binary
+    mv $out/bin/idris2_app/idris2.so $out/bin/idris2
+    # After moving the binary, there is nothing left in idris2_app that isn't
+    # either contained in lib/ or is useless to us.
+    rm $out/bin/idris2_app/*
+    rmdir $out/bin/idris2_app
+    # idris2 needs to find scheme at runtime to compile
+    # idris2 installs packages with --install into the path given by PREFIX.
+    # Since PREFIX is in nix-store, it is immutable so --install does not work.
+    # If the user redefines PREFIX to be able to install packages, idris2 will
+    # not find the libraries and packages since all paths are relative to
+    # PREFIX by default.
+    # We explicitly make all paths to point to nix-store, such that they are
+    # independent of what IDRIS2_PREFIX is. This allows the user to redefine
+    # IDRIS2_PREFIX and use --install as expected.
+    # TODO: Make support libraries their own derivation such that
+    #       overriding LD_LIBRARY_PATH is unnecessary
+    # TODO: Maybe set IDRIS2_PREFIX to the users home directory
+    wrapProgram "$out/bin/idris2" \
+      --set-default CHEZ "${chez}/bin/scheme" \
+      --suffix IDRIS2_LIBS ':' "$out/${name}/lib" \
+      --suffix IDRIS2_DATA ':' "$out/${name}/support" \
+      --suffix IDRIS2_PATH ':' "${additionalIdris2Paths}" \
+      --suffix LD_LIBRARY_PATH ':' "$out/${name}/lib"
+  '';
+}

result

@@ -0,0 +1 @@
+/nix/store/nw0mm1z2afpxv5rgf6w3apxc8pxwgd6h-idris2-0.3.0