Simplify nix setup

nix/default.nix

-{ sources ? import ./sources.nix
-}:
-let
-  # default nixpkgs
-  pkgs = import sources.nixpkgs { };
-
-  # gitignore.nix 
-  gitignoreSource = (import sources."gitignore.nix" { inherit (pkgs) lib; }).gitignoreSource;
-
-  pre-commit-hooks = (import sources."pre-commit-hooks.nix");
-
-  rust = (import ./rust.nix { inherit sources; });
-
-  src = gitignoreSource ./..;
-in
-{
-  inherit pkgs src;
-
-  # provided by shell.nix
-  devTools = with pkgs; with pre-commit-hooks; [
-    niv wasm-pack wasmtime valgrind protobuf clang llvm rocksdb
-    pre-commit nixpkgs-fmt nix-linter
-    rust
-  ];
-
-  # to be built by github actions
-  ci = {
-    pre-commit-check = pre-commit-hooks.run {
-      inherit src;
-      hooks = {
-        shellcheck.enable = true;
-        nixpkgs-fmt.enable = true;
-        nix-linter.enable = true;
-        cargo-check.enable = true;
-        rustfmt.enable = true;
-        clippy.enable = true;
-      };
-      # generated files
-      excludes = [ "^nix/sources\.nix$" ];
-    };
-  };
-}

nix/rust.nix

-{ sources ? import ./sources.nix }:
-let
-  pkgs =
-    import sources.nixpkgs { overlays = [ (import sources.nixpkgs-mozilla) ]; };
-  channel = "nightly";
-  date = "2021-03-18";
-  targets = [ "wasm32-unknown-unknown" "wasm32-wasi" ];
-  chan = pkgs.rustChannelOfTargets channel date targets;
-in
-chan

nix/sources.json

-{
-    "niv": {
-        "branch": "master",
-        "description": "Easy dependency management for Nix projects",
-        "homepage": "https://github.com/nmattia/niv",
-        "owner": "nmattia",
-        "repo": "niv",
-        "rev": "af958e8057f345ee1aca714c1247ef3ba1c15f5e",
-        "sha256": "1qjavxabbrsh73yck5dcq8jggvh3r2jkbr6b5nlz5d9yrqm9255n",
-        "type": "tarball",
-        "url": "https://github.com/nmattia/niv/archive/af958e8057f345ee1aca714c1247ef3ba1c15f5e.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "nixpkgs": {
-        "branch": "release-20.03",
-        "description": "Nix Packages collection",
-        "homepage": "",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "6d1a044fc9ff3cc96fca5fa3ba9c158522bbf2a5",
-        "sha256": "07a3nyrj3pwl017ig0rbn5rbmbf14gl3vqggvkyrdby01726p5fg",
-        "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/6d1a044fc9ff3cc96fca5fa3ba9c158522bbf2a5.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "nixpkgs-mozilla": {
-        "branch": "master",
-        "description": "mozilla related nixpkgs (extends nixos/nixpkgs repo)",
-        "homepage": "",
-        "owner": "mozilla",
-        "repo": "nixpkgs-mozilla",
-        "rev": "8c007b60731c07dd7a052cce508de3bb1ae849b4",
-        "sha256": "1zybp62zz0h077zm2zmqs2wcg3whg6jqaah9hcl1gv4x8af4zhs6",
-        "type": "tarball",
-        "url": "https://github.com/mozilla/nixpkgs-mozilla/archive/8c007b60731c07dd7a052cce508de3bb1ae849b4.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    },
-    "pre-commit-hooks.nix": {
-        "branch": "master",
-        "description": "Seamless integration of https://pre-commit.com git hooks with Nix.",
-        "homepage": "",
-        "owner": "cachix",
-        "repo": "pre-commit-hooks.nix",
-        "rev": "2d169bb1b23f3b71a894a66ea81f45c788943248",
-        "sha256": "1iyvi56rzszwizq0ymf1x262yhjwzk8k77qahb65fcync99jha2a",
-        "type": "tarball",
-        "url": "https://github.com/cachix/pre-commit-hooks.nix/archive/2d169bb1b23f3b71a894a66ea81f45c788943248.tar.gz",
-        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
-    }
-}

nix/sources.nix

-# This file has been generated by Niv.
-
-let
-
-  #
-  # The fetchers. fetch_<type> fetches specs of type <type>.
-  #
-
-  fetch_file = pkgs: spec:
-    if spec.builtin or true then
-      builtins_fetchurl { inherit (spec) url sha256; }
-    else
-      pkgs.fetchurl { inherit (spec) url sha256; };
-
-  fetch_tarball = pkgs: name: spec:
-    let
-      ok = str: ! builtins.isNull (builtins.match "[a-zA-Z0-9+-._?=]" str);
-      # sanitize the name, though nix will still fail if name starts with period
-      name' = stringAsChars (x: if ! ok x then "-" else x) "${name}-src";
-    in
-      if spec.builtin or true then
-        builtins_fetchTarball { name = name'; inherit (spec) url sha256; }
-      else
-        pkgs.fetchzip { name = name'; inherit (spec) url sha256; };
-
-  fetch_git = spec:
-    builtins.fetchGit { url = spec.repo; inherit (spec) rev ref; };
-
-  fetch_local = spec: spec.path;
-
-  fetch_builtin-tarball = name: throw
-    ''[${name}] The niv type "builtin-tarball" is deprecated. You should instead use `builtin = true`.
-        $ niv modify ${name} -a type=tarball -a builtin=true'';
-
-  fetch_builtin-url = name: throw
-    ''[${name}] The niv type "builtin-url" will soon be deprecated. You should instead use `builtin = true`.
-        $ niv modify ${name} -a type=file -a builtin=true'';
-
-  #
-  # Various helpers
-  #
-
-  # The set of packages used when specs are fetched using non-builtins.
-  mkPkgs = sources:
-    let
-      sourcesNixpkgs =
-        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) {};
-      hasNixpkgsPath = builtins.any (x: x.prefix == "nixpkgs") builtins.nixPath;
-      hasThisAsNixpkgsPath = <nixpkgs> == ./.;
-    in
-      if builtins.hasAttr "nixpkgs" sources
-      then sourcesNixpkgs
-      else if hasNixpkgsPath && ! hasThisAsNixpkgsPath then
-        import <nixpkgs> {}
-      else
-        abort
-          ''
-            Please specify either <nixpkgs> (through -I or NIX_PATH=nixpkgs=...) or
-            add a package called "nixpkgs" to your sources.json.
-          '';
-
-  # The actual fetching function.
-  fetch = pkgs: name: spec:
-
-    if ! builtins.hasAttr "type" spec then
-      abort "ERROR: niv spec ${name} does not have a 'type' attribute"
-    else if spec.type == "file" then fetch_file pkgs spec
-    else if spec.type == "tarball" then fetch_tarball pkgs name spec
-    else if spec.type == "git" then fetch_git spec
-    else if spec.type == "local" then fetch_local spec
-    else if spec.type == "builtin-tarball" then fetch_builtin-tarball name
-    else if spec.type == "builtin-url" then fetch_builtin-url name
-    else
-      abort "ERROR: niv spec ${name} has unknown type ${builtins.toJSON spec.type}";
-
-  # If the environment variable NIV_OVERRIDE_${name} is set, then use
-  # the path directly as opposed to the fetched source.
-  replace = name: drv:
-    let
-      saneName = stringAsChars (c: if isNull (builtins.match "[a-zA-Z0-9]" c) then "_" else c) name;
-      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
-    in
-      if ersatz == "" then drv else ersatz;
-
-  # Ports of functions for older nix versions
-
-  # a Nix version of mapAttrs if the built-in doesn't exist
-  mapAttrs = builtins.mapAttrs or (
-    f: set: with builtins;
-    listToAttrs (map (attr: { name = attr; value = f attr set.${attr}; }) (attrNames set))
-  );
-
-  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/lists.nix#L295
-  range = first: last: if first > last then [] else builtins.genList (n: first + n) (last - first + 1);
-
-  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L257
-  stringToCharacters = s: map (p: builtins.substring p 1 s) (range 0 (builtins.stringLength s - 1));
-
-  # https://github.com/NixOS/nixpkgs/blob/0258808f5744ca980b9a1f24fe0b1e6f0fecee9c/lib/strings.nix#L269
-  stringAsChars = f: s: concatStrings (map f (stringToCharacters s));
-  concatStrings = builtins.concatStringsSep "";
-
-  # fetchTarball version that is compatible between all the versions of Nix
-  builtins_fetchTarball = { url, name, sha256 }@attrs:
-    let
-      inherit (builtins) lessThan nixVersion fetchTarball;
-    in
-      if lessThan nixVersion "1.12" then
-        fetchTarball { inherit name 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;
-
-  # Create the final "sources" from the config
-  mkSources = config:
-    mapAttrs (
-      name: spec:
-        if builtins.hasAttr "outPath" spec
-        then abort
-          "The values in sources.json should not have an 'outPath' attribute"
-        else
-          spec // { outPath = replace name (fetch config.pkgs name spec); }
-    ) config.sources;
-
-  # The "config" used by the fetchers
-  mkConfig =
-    { sourcesFile ? if builtins.pathExists ./sources.json then ./sources.json else null
-    , sources ? if isNull sourcesFile then {} else builtins.fromJSON (builtins.readFile sourcesFile)
-    , pkgs ? mkPkgs sources
-    }: rec {
-      # The sources, i.e. the attribute set of spec name to spec
-      inherit sources;
-
-      # The "pkgs" (evaluated nixpkgs) to use for e.g. non-builtin fetchers
-      inherit pkgs;
-    };
-
-in
-mkSources (mkConfig {}) // { __functor = _: settings: mkSources (mkConfig settings); }

shell.nix

-{ project ? import ./nix/default.nix { }
-}:
+let
+  mozillaOverlay =
+    import (builtins.fetchGit {
+      url = "https://github.com/mozilla/nixpkgs-mozilla.git";
+      rev = "57c8084c7ef41366993909c20491e359bbb90f54";
+    });
+  pinned = builtins.fetchGit {
+    # Descriptive name to make the store path easier to identify
+    name = "nixos-unstable-2020-04-26";
+    url = "https://github.com/nixos/nixpkgs/";
+    # Commit hash for nixos-unstable as of 2020-04-26
+    # `git ls-remote https://github.com/nixos/nixpkgs nixos-unstable`
+    ref = "refs/heads/nixos-unstable";
+    rev = "1fe6ed37fd9beb92afe90671c0c2a662a03463dd";
+  };
+  nixpkgs = import pinned { overlays = [ mozillaOverlay ]; };
+  rust-nightly = with nixpkgs; ((rustChannelOf { date = "2021-03-01"; channel = "nightly"; }).rust.override {
+    targets = [ "wasm32-unknown-unknown" ];
+  });
+in
+with nixpkgs; pkgs.mkShell {
+  buildInputs = [
+    clang
+    pkg-config
+    rust-nightly
+  ] ++ stdenv.lib.optionals stdenv.isDarwin [
+    darwin.apple_sdk.frameworks.Security
+  ];
 
-project.pkgs.mkShell {
-  buildInputs = project.devTools;
-  LIBCLANG_PATH = "${project.pkgs.llvmPackages.libclang}/lib/libclang.so";
-  PROTOC = "${project.pkgs.protobuf}/bin/protoc";
-  ROCKSDB = "${project.pkgs.rocksdb}/lib/librocksdb.so";
+  LIBCLANG_PATH = "${llvmPackages.libclang}/lib";
+  PROTOC = "${protobuf}/bin/protoc";
+  ROCKSDB_LIB_DIR = "${rocksdb}/lib";
 }