Refactor nix flake, based on overriding nixpkgs

Now that umu-launcher-unwrapped is being maintained in nixpkgs, it can
be used as a starting point for the nix package here. We just need to
override a few things, such as the `src`, and handle any changes that
have not yet made it into a release build.

Ideally, we would also reuse the nixpkgs umu-launcher wrapper package.
However, 1) it is currently not fully overridable and 2) we have a
slightly different package-args API that needs to be maintained.

The opportunity has been taken to clean up that package-args API:
- Renamed `truststore` to `withTruststore` with a warning.
- `cbor2` wasn't working, warn when it is used.
- Added `withDeltaUpdates`

Breaking changes:
- The umu-launcher package in the overlay is no longer the unwrapped
  package (previously in `umu-launcher.nix`).
- The derivation attrs for various packages are re-written from scratch,
  likely breaking users' custom overrides.

Non-breaking changes:
- The umu & umu-run packages have effectively been renamed umu-launcher.
- The flake outputs for all systems supported by the nixpkgs package.
- The package version is now derived from the flake's lastModifiedDate.

README.md

@@ -155,21 +155,39 @@ and in your `configuration.nix`
 {inputs, pkgs, ... }:
 let
   inherit (pkgs.stdenv.hostPlatform) system;
-  umu = inputs.umu.packages.${system}.umu.override {
+  unu-launcher = inputs.umu.packages.${system}.default;
+in
+{
+  environment.systemPackages = [ umu-launcher ];
+}
+```
+
+> [!TIP]
+> It is common practice to override umu's `version` to `inputs.umu.shortRev` (the umu git commit). By default, the version is based on `inputs.umu`'s last modified date.
+> e.g. `"git.2025.01.22.09.59.33"`.
+
+> [!TIP]
+> `withTruststore` and `withDeltaUpdates` can be used to disable optional dependencies that are enabled by default.
+> You can omit these, or set them to `false` if you do not want these dependencies.
+
+Example:
+```nix
+{inputs, pkgs, ... }:
+let
+  inherit (pkgs.stdenv.hostPlatform) system;
+  umu-launcher = inputs.umu.packages.${system}.default.override {
     version = inputs.umu.shortRev;
-    truststore = true;
-    cbor2 = true;
+    withTruststore = false;
+    withDeltaUpdates = false;
   };
 in
 {
-  environment.systemPackages = [ umu ];
+  environment.systemPackages = [ umu-launcher ];
 }
 ```
-> [!NOTE]
-> truststore and cbor2 (for delta updates) are optional dependency which are enabled by default if you want to keep it that way you can remove the `truststore = true; cbor2 = true;` part
 
 > [!NOTE]
-> The example above relies on having your flake's `inputs` passed through to your nixos configuration.
+> The examples above rely on having your flake's `inputs` passed through to your nixos configuration.
 > This can be done with `specialArgs` or `_module.args`, e.g:
 > ```nix
 > {

packaging/nix/flake.nix

@@ -9,43 +9,43 @@
     self,
     nixpkgs,
   }: let
-    umu-launcher-src = builtins.toPath "${self}/../../";
-
-    pkgs = import nixpkgs {
-      system = "x86_64-linux";
-      overlays = [self.overlays.default];
-    };
-
-    version = "1.1.4";
+    inherit (nixpkgs) lib;
+
+    # Utility function for producing consistent rename warning messages
+    rename = old: new: lib.warn "`${old}` has been renamed to `${new}`";
+
+    # Package sets supported by umu-launcher-unwrapped
+    # { system = pkgs; }
+    supportedPkgs =
+      lib.filterAttrs
+      (system: pkgs: builtins.elem system pkgs.umu-launcher-unwrapped.meta.platforms)
+      nixpkgs.legacyPackages;
+
+    # Generate a version string, based on the flake's lastModifiedDate
+    version = let
+      date = self.lastModifiedDate;
+      parts = builtins.match "(\[0-9\]{4})(\[0-9\]{2})(\[0-9\]{2})(\[0-9\]{2})(\[0-9\]{2})(\[0-9\]{2})" date;
+    in "git.${lib.concatStringsSep "." parts}";
   in {
-    overlays.default = final: prev: let
-      py = prev.python3;
-    in {
-      umu-launcher = final.callPackage ./umu-launcher.nix {
-        inherit version;
-        umu-launcher = umu-launcher-src;
-        pyth1 = py;
-      };
-
-      umu-run = final.callPackage ./umu-run.nix {
+    overlays.default = final: prev: {
+      umu-launcher = final.callPackage ./package.nix {
         inherit version;
-        package = final.umu-launcher;
-      };
-
-      umu = final.callPackage ./combine.nix {
-        inherit version;
-        env = final.umu-run;
-        package = final.umu-launcher;
-        truststore = true;
-        cbor2 = true;
+        inherit (prev) umu-launcher-unwrapped;
       };
+      umu = rename "umu" "umu-launcher" final.umu-launcher;
+      umu-run = rename "umu-run" "umu-launcher" final.umu-launcher;
+      inherit (final.umu-launcher.passthru) umu-launcher-unwrapped;
     };
 
     formatter = builtins.mapAttrs (system: pkgs: pkgs.alejandra) nixpkgs.legacyPackages;
 
-    packages.x86_64-linux = {
-      inherit (pkgs) umu;
-      default = self.packages.x86_64-linux.umu;
-    };
+    packages =
+      builtins.mapAttrs (system: pkgs: rec {
+        default = umu-launcher;
+        umu-launcher = pkgs.callPackage ./package.nix {inherit version;};
+        umu = rename "packages.${system}.umu" "packages.${system}.umu-launcher" umu-launcher;
+        inherit (umu-launcher.passthru) umu-launcher-unwrapped;
+      })
+      supportedPkgs;
   };
 }

packaging/nix/package.nix

@@ -0,0 +1,82 @@
+{
+  # Dependencies:
+  lib,
+  buildFHSEnv,
+  umu-launcher-unwrapped,
+  python3Packages,
+  rustPlatform,
+  cargo,
+  zstd,
+  # Public API:
+  version,
+  withTruststore ? args.truststore or true,
+  withDeltaUpdates ? true,
+  # Deprecated:
+  # NOTE: this relies on there not being a `pkgs.truststore` or `pkgs.cbor2`...
+  # If there was, callPackage would provide them, causing our warnings to false-positive.
+  truststore ? null,
+  cbor2 ? null,
+} @ args: let
+  checked = {
+    withTruststore =
+      lib.warnIf (args ? truststore)
+      "umu-launcher: the argument `truststore` has been renamed to `withTruststore`."
+      withTruststore;
+    withDeltaUpdates =
+      lib.warnIf (args ? cbor2)
+      "umu-launcher: the argument `cbor2` has never had any effect. The new argument `withDeltaUpdates` should be used instead."
+      withDeltaUpdates;
+  };
+
+  overridden = umu-launcher-unwrapped.overridePythonAttrs (prev: {
+    src = ../../.;
+    inherit version;
+
+    # We can drop old.patches and replace it with the patches we actually need
+    patches = [
+      ./0-Makefile-no-vendor.patch
+    ];
+
+    nativeBuildInputs =
+      (prev.nativeBuildInputs or [])
+      ++ [
+        rustPlatform.cargoSetupHook
+        cargo
+      ];
+
+    propagatedBuildInputs =
+      (prev.propagatedBuildInputs or [])
+      ++ lib.optionals checked.withTruststore [
+        python3Packages.truststore
+      ]
+      ++ lib.optionals checked.withDeltaUpdates [
+        python3Packages.cbor2
+        python3Packages.xxhash
+        zstd
+      ];
+
+    cargoDeps = rustPlatform.importCargoLock {
+      lockFile = ../../Cargo.lock;
+    };
+  });
+in
+  # We cannot override everything we need to, so re-implement the package
+  # See https://github.com/NixOS/nixpkgs/pull/375588
+  # Tracker https://nixpk.gs/pr-tracker.html?pr=375588
+  buildFHSEnv {
+    pname = "umu-launcher";
+    inherit (overridden) version meta;
+    executableName = overridden.meta.mainProgram;
+
+    targetPkgs = pkgs: [overridden];
+    runScript = lib.getExe overridden;
+
+    extraInstallCommands = ''
+      ln -s ${overridden}/lib $out/lib
+      ln -s ${overridden}/share $out/share
+    '';
+
+    # For debugging and to simplify the overlay,
+    # expose the overridden unwrapped package
+    passthru.umu-launcher-unwrapped = overridden;
+  }