Clean up Nix Flake & make it easier to customize (#12831)

default.nix

@@ -1,8 +1,78 @@
-# Flake's default package for non-flake-enabled nix instances
-let
-  compat = builtins.fetchTarball {
-    url = "https://github.com/edolstra/flake-compat/archive/b4a34015c698c7793d592d66adbab377907a2be8.tar.gz";
-    sha256 = "sha256:1qc703yg0babixi6wshn5wm2kgl5y1drcswgszh4xxzbrwkk9sv7";
-  };
+{
+  lib,
+  rustPlatform,
+  callPackage,
+  runCommand,
+  installShellFiles,
+  git,
+  ...
+}: let
+  fs = lib.fileset;
+
+  src = fs.difference (fs.gitTracked ./.) (fs.unions [
+    ./.envrc
+    ./rustfmt.toml
+    ./screenshot.png
+    ./book
+    ./docs
+    ./flake.lock
+    (fs.fileFilter (file: lib.strings.hasInfix ".git" file.name) ./.)
+    (fs.fileFilter (file: file.hasExt "svg") ./.)
+    (fs.fileFilter (file: file.hasExt "md") ./.)
+    (fs.fileFilter (file: file.hasExt "nix") ./.)
+  ]);
+
+  # Next we actually need to build the grammars and the runtime directory
+  # that they reside in. It is built by calling the derivation in the
+  # grammars.nix file, then taking the runtime directory in the git repo
+  # and hooking symlinks up to it.
+  grammars = callPackage ./grammars.nix {};
+  runtimeDir = runCommand "helix-runtime" {} ''
+    mkdir -p $out
+    ln -s ${./runtime}/* $out
+    rm -r $out/grammars
+    ln -s ${grammars} $out/grammars
+  '';
 in
-  (import compat {src = ./.;}).defaultNix
+  # Currently rustPlatform.buildRustPackage doesn't have the finalAttrs pattern
+  # hooked up. To get around this while having good customization, mkDerivation is
+  # used instead.
+  rustPlatform.buildRustPackage (self: {
+    cargoLock.lockFile = ./Cargo.lock;
+
+    nativeBuildInputs = [
+      installShellFiles
+      git
+    ];
+
+    buildType = "release";
+
+    name = with builtins; (fromTOML (readFile ./helix-term/Cargo.toml)).package.name;
+    src = fs.toSource {
+      root = ./.;
+      fileset = src;
+    };
+
+    # Helix attempts to reach out to the network and get the grammars. Nix doesn't allow this.
+    HELIX_DISABLE_AUTO_GRAMMAR_BUILD = "1";
+
+    # So Helix knows what rev it is.
+    HELIX_NIX_BUILD_REV = self.rev or self.dirtyRev or null;
+
+    doCheck = false;
+    strictDeps = true;
+
+    # Sets the Helix runtimedir to the grammars
+    env.HELIX_DEFAULT_RUNTIME = "${runtimeDir}";
+
+    # Get all the application stuff in the output directory.
+    postInstall = ''
+      mkdir -p $out/lib
+      installShellCompletion ${./contrib/completion}/hx.{bash,fish,zsh}
+      mkdir -p $out/share/{applications,icons/hicolor/256x256/apps}
+      cp ${./contrib/Helix.desktop} $out/share/applications
+      cp ${./contrib/helix.png} $out/share/icons/hicolor/256x256/apps
+    '';
+
+    meta.mainProgram = "hx";
+  })