WIP: use niv for source management

nix/overlay.nix

@@ -2,6 +2,8 @@ self: super:
 
 let
   nixpkgs-master = import <nixpkgs-master> {};
+  # sources = import ./sources.nix;
+  # nixpkgs-master = sources.nixpkgs-master;
 
   # one application requires php5
   nixpkgsWithPhp5 = super.fetchFromGitHub {
@@ -23,8 +25,6 @@ in {
     '';
   };
 
-
-
   podman = nixpkgs-master.podman;
   conmon = nixpkgs-master.conmon;
 

nix/package-set.nix

@@ -0,0 +1,8 @@
+{ pkgs }:
+
+with pkgs.lib;
+let
+  self = foldl'
+    (prev: overlay: prev // (overlay (pkgs // self) (pkgs // prev)))
+    {} (map import (import ./overlays.nix));
+in self

nix/sources.json

@@ -0,0 +1,38 @@
+{
+    "niv": {
+        "branch": "master",
+        "description": "Easy dependency management for Nix projects",
+        "homepage": "https://github.com/nmattia/niv",
+        "owner": "nmattia",
+        "repo": "niv",
+        "rev": "5e9671a9a87c240b1c6ce981d04ad23ba4291451",
+        "sha256": "08j7msxkv452pyxnh0sgn6h9930i5mk9mszba49bj5401gzmfb8a",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/niv/archive/5e9671a9a87c240b1c6ce981d04ad23ba4291451.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixos-19.03",
+        "description": "A read-only mirror of NixOS/nixpkgs tracking the released channels. Send issues and PRs to",
+        "homepage": "https://github.com/NixOS/nixpkgs",
+        "owner": "NixOS",
+        "repo": "nixpkgs-channels",
+        "rev": "7339bd47600f687dac692fea897bbf58c55631c4",
+        "sha256": "12nxr39pjhd8n0l91wsv1kvzdsa5zhhc5a0hndbi1zyxjdrlqsxa",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs-channels/archive/7339bd47600f687dac692fea897bbf58c55631c4.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs-master": {
+        "branch": "master",
+        "description": "Nix Packages collection",
+        "homepage": null,
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "92e653b19b613bba25cdd7367fe039697d70ecdf",
+        "sha256": "0aiq94nsyxwcal2f7kclb70fggzmw39gkz3l2cs384sv1kw4dmck",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/92e653b19b613bba25cdd7367fe039697d70ecdf.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    }
+}

nix/sources.nix

@@ -0,0 +1,89 @@
+# This file has been generated by Niv.
+
+# A record, from name to path, of the third-party packages
+with rec
+{
+  pkgs =
+    if hasNixpkgsPath
+    then
+        if hasThisAsNixpkgsPath
+        then import (builtins_fetchTarball { inherit (sources_nixpkgs) url sha256; }) {}
+        else import <nixpkgs> {}
+    else
+        import (builtins_fetchTarball { inherit (sources_nixpkgs) url sha256; }) {};
+
+  sources_nixpkgs =
+    if builtins.hasAttr "nixpkgs" sources
+    then sources.nixpkgs
+    else abort
+    ''
+        Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
+        add a package called "nixpkgs" to your sources.json.
+    '';
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball =
+      { url, sha256 }@attrs:
+      let
+        inherit (builtins) lessThan nixVersion fetchTarball;
+      in
+        if lessThan nixVersion "1.12" then
+          fetchTarball { inherit url; }
+        else
+          fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl =
+      { url, sha256 }@attrs:
+      let
+        inherit (builtins) lessThan nixVersion fetchurl;
+      in
+        if lessThan nixVersion "1.12" then
+          fetchurl { inherit url; }
+        else
+          fetchurl attrs;
+
+  # A wrapper around pkgs.fetchzip that has inspectable arguments,
+  # annoyingly this means we have to specify them
+  fetchzip = { url, sha256 }@attrs: pkgs.fetchzip attrs;
+
+  hasNixpkgsPath = (builtins.tryEval <nixpkgs>).success;
+  hasThisAsNixpkgsPath =
+    (builtins.tryEval <nixpkgs>).success && <nixpkgs> == ./.;
+
+  sources = builtins.fromJSON (builtins.readFile ./sources.json);
+
+  mapAttrs = builtins.mapAttrs or
+    (f: set: with builtins;
+      listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set)));
+
+  # borrowed from nixpkgs
+  functionArgs = f: f.__functionArgs or (builtins.functionArgs f);
+  callFunctionWith = autoArgs: f: args:
+    let auto = builtins.intersectAttrs (functionArgs f) autoArgs;
+    in f (auto // args);
+
+  getFetcher = spec:
+    let fetcherName =
+      if builtins.hasAttr "type" spec
+      then builtins.getAttr "type" spec
+      else "builtin-tarball";
+    in builtins.getAttr fetcherName {
+      "tarball" = fetchzip;
+      "builtin-tarball" = builtins_fetchTarball;
+      "file" = pkgs.fetchurl;
+      "builtin-url" = builtins_fetchurl;
+    };
+};
+# NOTE: spec must _not_ have an "outPath" attribute
+mapAttrs (_: spec:
+  if builtins.hasAttr "outPath" spec
+  then abort
+    "The values in sources.json should not have an 'outPath' attribute"
+  else
+    if builtins.hasAttr "url" spec && builtins.hasAttr "sha256" spec
+    then
+      spec //
+      { outPath = callFunctionWith spec (getFetcher spec) { }; }
+    else spec
+  ) sources

shell.nix

@@ -4,6 +4,12 @@ let
   channels-nixos-stable-path = (builtins.fetchTarball https://github.com/NixOS/nixpkgs-channels/archive/7e88992a8c7b2de0bcb89182d8686b27bd93e46a.tar.gz);
   channels-nixos-stable = import channels-nixos-stable-path { overlays = [ (import ./nix/overlay.nix) ]; };
 
+  niv = (import (channels-nixos-stable.fetchFromGitHub {
+    owner = "nmattia";
+    repo = "niv";
+    rev = "5e9671a9a87c240b1c6ce981d04ad23ba4291451";
+    sha256 = "08j7msxkv452pyxnh0sgn6h9930i5mk9mszba49bj5401gzmfb8a";
+  }) {}).niv;
 in
 with channels-nixos-stable;
 stdenv.mkDerivation {
@@ -26,6 +32,7 @@ stdenv.mkDerivation {
 
     # testing
     alacritty
+    niv
   ];
 
   # Set Environment Variables