Nix: Add skeleton

default.nix

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+{ nixpkgs ? import ./nix/nixpkgs.nix {} }:
+
+with nixpkgs.pkgs;
+with gitignore;
+
+haskellPackages.callCabal2nix "clash-protocols" (gitignoreSource ./.) {}

nix/nixpkgs.nix

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+{ sources ? import ./sources.nix }:
+
+let
+  overlay = _: pkgs: {
+
+    # Nix tooling
+    niv = (import sources.niv {}).niv;
+    gitignore = import sources.gitignore { inherit (pkgs) lib; };
+
+    # Haskell overrides
+    haskellPackages = pkgs.haskellPackages.override {
+      overrides = self: super: {
+        # Add overrides here
+        circuit-notation =
+          self.callCabal2nix "circuit-notation" sources.circuit-notation {};
+        doctest-parallel =
+          self.callCabal2nix "doctest-parallel" sources.doctest-parallel {};
+        clash-prelude =
+          pkgs.haskell.lib.dontCheck (self.callCabal2nix "clash-prelude" (sources.clash-compiler + "/clash-prelude") {});
+        clash-lib =
+          self.callCabal2nix "clash-lib" (sources.clash-compiler + "/clash-lib") {};
+        clash-ghc =
+          self.callCabal2nix "clash-ghc" (sources.clash-compiler + "/clash-ghc") {};
+        clash-prelude-hedgehog =
+          self.callCabal2nix "clash-prelude" (sources.clash-compiler + "/clash-prelude-hedgehog") {};
+        tasty-hedgehog =
+          self.callCabal2nix "tasty-hedgehog" sources.tasty-hedgehog {};
+        hedgehog =
+          self.callCabal2nix "hedgehog" (sources.haskell-hedgehog + "/hedgehog") {};
+      };
+    };
+  };
+
+in import sources.nixpkgs { overlays = [ overlay ]; }

nix/sources.json

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+{
+    "clash-compiler": {
+        "branch": "1.8",
+        "description": "Haskell to VHDL/Verilog/SystemVerilog compiler",
+        "homepage": "https://clash-lang.org/",
+        "owner": "clash-lang",
+        "repo": "clash-compiler",
+        "rev": "3f5dc67c0e526e43a4dd88eb3902e39ed512c166",
+        "sha256": "022rwif8xkaabw0j3arhyj0hswmh3vq2nx1bbz8rbkp05jm4psgg",
+        "type": "tarball",
+        "url": "https://github.com/clash-lang/clash-compiler/archive/3f5dc67c0e526e43a4dd88eb3902e39ed512c166.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "version": "1.8.1"
+    },
+    "doctest-parallel": {
+        "branch": "main",
+        "description": "Test interactive Haskell examples",
+        "homepage": null,
+        "owner": "martijnbastiaan",
+        "repo": "doctest-parallel",
+        "rev": "d73df0a2fd58b0b6aba438eb40aa56d30724e42a",
+        "sha256": "1k88bkwz2crvb6dafcf6y5y6wm0m2qvds57f3b0rx4id7la4qv89",
+        "type": "tarball",
+        "url": "https://github.com/martijnbastiaan/doctest-parallel/archive/d73df0a2fd58b0b6aba438eb40aa56d30724e42a.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "version": "0.3.1"
+    },
+    "gitignore": {
+        "branch": "master",
+        "description": "Nix function for filtering local git sources",
+        "homepage": "",
+        "owner": "hercules-ci",
+        "repo": "gitignore",
+        "rev": "bff2832ec341cf30acb3a4d3e2e7f1f7b590116a",
+        "sha256": "0va0janxvmilm67nbl81gdbpppal4aprxzb25gp9pqvf76ahxsci",
+        "type": "tarball",
+        "url": "https://github.com/hercules-ci/gitignore/archive/bff2832ec341cf30acb3a4d3e2e7f1f7b590116a.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "haskell-hedgehog": {
+        "branch": "master",
+        "description": "Release with confidence, state-of-the-art property testing for Haskell.",
+        "homepage": "",
+        "owner": "hedgehogqa",
+        "repo": "haskell-hedgehog",
+        "rev": "52c35cabe24de2a1c03e72dde9d04b64f81d1f44",
+        "sha256": "1f9znljkmrdd4nlfmjfi8kx0fgcysp328rz27099n7bygchpgjr6",
+        "type": "tarball",
+        "url": "https://github.com/hedgehogqa/haskell-hedgehog/archive/52c35cabe24de2a1c03e72dde9d04b64f81d1f44.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "version": "1.4"
+    },
+    "circuit-notation": {
+        "branch": "master",
+        "description": "A plugin for circuit notation",
+        "homepage": null,
+        "owner": "cchalmers",
+        "repo": "circuit-notation",
+        "rev": "19b386c4aa3ff690758ae089c7754303f3500cc9",
+        "sha256": "0qz2w6akxj51kq50rbl88bnjyxzd2798a9sn9jj1z2kak7a6kqbg",
+        "type": "tarball",
+        "url": "https://github.com/cchalmers/circuit-notation/archive/19b386c4aa3ff690758ae089c7754303f3500cc9.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "niv": {
+        "branch": "master",
+        "description": "Easy dependency management for Nix projects",
+        "homepage": "https://github.com/nmattia/niv",
+        "owner": "nmattia",
+        "repo": "niv",
+        "rev": "723f0eeb969a730db3c30f977c2b66b9dce9fe4a",
+        "sha256": "0016l7230gd2kdh0g2w573r9a2krqb7x4ifcjhhsn4h1bwap7qr0",
+        "type": "tarball",
+        "url": "https://github.com/nmattia/niv/archive/723f0eeb969a730db3c30f977c2b66b9dce9fe4a.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs": {
+        "branch": "nixpkgs-unstable",
+        "description": "Nix Packages collection",
+        "homepage": "",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "e2dd4e18cc1c7314e24154331bae07df76eb582f",
+        "sha256": "19zbxf7rb787jvyrfhl4z9sn3aisd6xvx6ikybbi75ym9sy39jds",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/e2dd4e18cc1c7314e24154331bae07df76eb582f.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "tasty-hedgehog": {
+        "branch": "master",
+        "description": "Tasty integration for the Hedgehog property testing library",
+        "homepage": "",
+        "owner": "qfpl",
+        "repo": "tasty-hedgehog",
+        "rev": "ed07ecef3f6a01572b577b450ba6d58108173125",
+        "sha256": "1b8y5ibg1ihgf44nyym4g45lwmabymfcjb2nigv93s2fmng9zp6r",
+        "type": "tarball",
+        "url": "https://github.com/qfpl/tasty-hedgehog/archive/ed07ecef3f6a01572b577b450ba6d58108173125.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "version": "1.4.0.2"
+    }
+}

nix/sources.nix

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+# This file has been generated by Niv.
+
+let
+
+  #
+  # The fetchers. fetch_<type> fetches specs of type <type>.
+  #
+
+  fetch_file = pkgs: name: spec:
+    let
+      name' = sanitizeName name + "-src";
+    in
+    if spec.builtin or true then
+      builtins_fetchurl { inherit (spec) url sha256; name = name'; }
+    else
+      pkgs.fetchurl { inherit (spec) url sha256; name = name'; };
+
+  fetch_tarball = pkgs: name: spec:
+    let
+      name' = sanitizeName 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 = name: spec:
+    let
+      ref =
+        spec.ref or (
+          if spec ? branch then "refs/heads/${spec.branch}" else
+          if spec ? tag then "refs/tags/${spec.tag}" else
+          abort "In git source '${name}': Please specify `ref`, `tag` or `branch`!"
+        );
+      submodules = spec.submodules or false;
+      submoduleArg =
+        let
+          nixSupportsSubmodules = builtins.compareVersions builtins.nixVersion "2.4" >= 0;
+          emptyArgWithWarning =
+            if submodules
+            then
+              builtins.trace
+                (
+                  "The niv input \"${name}\" uses submodules "
+                  + "but your nix's (${builtins.nixVersion}) builtins.fetchGit "
+                  + "does not support them"
+                )
+                { }
+            else { };
+        in
+        if nixSupportsSubmodules
+        then { inherit submodules; }
+        else emptyArgWithWarning;
+    in
+    builtins.fetchGit
+      ({ url = spec.repo; inherit (spec) rev; inherit ref; } // submoduleArg);
+
+  fetch_local = spec: spec.path;
+
+  fetch_builtin-tarball = name: throw
+    ''[${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
+  #
+
+  # https://github.com/NixOS/nixpkgs/pull/83241/files#diff-c6f540a4f3bfa4b0e8b6bafd4cd54e8bR695
+  sanitizeName = name:
+    (
+      concatMapStrings (s: if builtins.isList s then "-" else s)
+        (
+          builtins.split "[^[:alnum:]+._?=-]+"
+            ((x: builtins.elemAt (builtins.match "\\.*(.*)" x) 0) name)
+        )
+    );
+
+  # The set of packages used when specs are fetched using non-builtins.
+  mkPkgs = sources: system:
+    let
+      sourcesNixpkgs =
+        import (builtins_fetchTarball { inherit (sources.nixpkgs) url sha256; }) { inherit system; };
+      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 name spec
+    else if spec.type == "tarball" then fetch_tarball pkgs name spec
+    else if spec.type == "git" then fetch_git name 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 (builtins.match "[a-zA-Z0-9]" c) == null then "_" else c) name;
+      ersatz = builtins.getEnv "NIV_OVERRIDE_${saneName}";
+    in
+    if ersatz == "" then drv else
+      # this turns the string into an actual Nix path (for both absolute and
+      # relative paths)
+    if builtins.substring 0 1 ersatz == "/" then /. + ersatz else /. + builtins.getEnv "PWD" + "/${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));
+  concatMapStrings = f: list: concatStrings (map f list);
+  concatStrings = builtins.concatStringsSep "";
+
+  # https://github.com/NixOS/nixpkgs/blob/8a9f58a375c401b96da862d969f66429def1d118/lib/attrsets.nix#L331
+  optionalAttrs = cond: as: if cond then as else { };
+
+  # fetchTarball version that is compatible between all the versions of Nix
+  builtins_fetchTarball = { url, name ? null, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchTarball;
+    in
+    if lessThan nixVersion "1.12" then
+      fetchTarball ({ inherit url; } // (optionalAttrs (name != null) { inherit name; }))
+    else
+      fetchTarball attrs;
+
+  # fetchurl version that is compatible between all the versions of Nix
+  builtins_fetchurl = { url, name ? null, sha256 }@attrs:
+    let
+      inherit (builtins) lessThan nixVersion fetchurl;
+    in
+    if lessThan nixVersion "1.12" then
+      fetchurl ({ inherit url; } // (optionalAttrs (name != null) { inherit name; }))
+    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 sourcesFile == null then { } else builtins.fromJSON (builtins.readFile sourcesFile)
+    , system ? builtins.currentSystem
+    , pkgs ? mkPkgs sources system
+    }: 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); }

release.nix

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+let
+  pkgs = import ./nix/nixpkgs.nix { };
+in
+  pkgs.haskellPackages.callPackage ./default.nix { }

shell.nix

@@ -0,0 +1,16 @@
+{ nixpkgs ? import ./nix/nixpkgs.nix {} }:
+let
+  inherit (nixpkgs) pkgs;
+  inherit (pkgs) haskellPackages;
+
+  project = import ./release.nix;
+in
+
+pkgs.stdenv.mkDerivation {
+  name = "shell";
+  buildInputs = project.env.nativeBuildInputs ++ [
+    haskellPackages.cabal-install
+    haskellPackages.fourmolu
+  ];
+  LC_ALL = "C.UTF-8";
+}