Set up Nix development

.envrc

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+use nix
+watch_file flake.nix
+watch_file shell.nix
+watch_file flake.lock
+watch_file .envrc

flake.nix

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+# Copyright (c) 2022 Espresso Systems (espressosys.com)
+# This file is part of the Tide Disco library.
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU
+# General Public License as published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
+# even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# General Public License for more details.
+# You should have received a copy of the GNU General Public License along with this program. If not,
+# see <https://www.gnu.org/licenses/>.
+
+{
+  description = "Development shell for Tide Disco";
+
+  inputs.nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
+
+  inputs.flake-utils.url = "github:numtide/flake-utils";
+
+  inputs.flake-compat.url = "github:edolstra/flake-compat";
+  inputs.flake-compat.flake = false;
+
+  inputs.rust-overlay.url = "github:oxalica/rust-overlay";
+
+  inputs.fenix.url = "github:nix-community/fenix";
+  inputs.fenix.inputs.nixpkgs.follows = "nixpkgs";
+
+  outputs = { self, nixpkgs, flake-utils, flake-compat, rust-overlay, fenix, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        info = builtins.split "\([a-zA-Z0-9_]+\)" system;
+        arch = (builtins.elemAt (builtins.elemAt info 1) 0);
+        os = (builtins.elemAt (builtins.elemAt info 3) 0);
+        overlays = [ (import rust-overlay) ];
+        pkgs = import nixpkgs { inherit system overlays; };
+        rustToolchain = pkgs.rust-bin.stable.latest.minimal.override {
+          extensions = [ "rustfmt" "clippy" "llvm-tools-preview" "rust-src" ];
+        };
+        rustDeps = with pkgs;
+          [
+            pkgconfig
+            openssl
+            bash
+
+            curl
+
+            cargo-edit
+            cargo-udeps
+            cargo-sort
+            cmake
+          ] ++ lib.optionals stdenv.isDarwin [
+            darwin.apple_sdk.frameworks.Security
+            darwin.apple_sdk.frameworks.CoreFoundation
+            darwin.apple_sdk.frameworks.SystemConfiguration
+
+            # https://github.com/NixOS/nixpkgs/issues/126182
+            libiconv
+          ] ++ lib.optionals (stdenv.system != "aarch64-darwin") [
+            cargo-watch # broken: https://github.com/NixOS/nixpkgs/issues/146349
+          ];
+        # nixWithFlakes allows pre v2.4 nix installations to use
+        # flake commands (like `nix flake update`)
+        nixWithFlakes = pkgs.writeShellScriptBin "nix" ''
+          exec ${pkgs.nixFlakes}/bin/nix --experimental-features "nix-command flakes" "$@"
+        '';
+        shellHook  = ''
+          # on mac os `bin/pwd -P` returns the canonical path on case insensitive file-systems
+          my_pwd=$(/bin/pwd -P 2> /dev/null || pwd)
+
+          export PATH=${pkgs.xdot}/bin:$PATH
+          export PATH=''${my_pwd}/bin:$PATH
+        '';
+      in {
+        devShell = pkgs.mkShell {
+          shellHook = shellHook;
+          buildInputs = with pkgs;
+            [
+              fenix.packages.${system}.rust-analyzer
+              nixWithFlakes
+              nixpkgs-fmt
+              git
+              mdbook # make-doc, documentation generation
+              rustToolchain
+            ] ++ rustDeps;
+
+          RUST_SRC_PATH = "${rustToolchain}/lib/rustlib/src/rust/library";
+          RUST_BACKTRACE = 1;
+          RUST_LOG = "info";
+        };
+      });
+}

shell.nix

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+(import
+  (
+    let
+      lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+    in
+    fetchTarball {
+      url = "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+      sha256 = lock.nodes.flake-compat.locked.narHash;
+    }
+  )
+  {
+    src = ./.;
+  }).shellNix