meta: add fetchModrinthModpack

README.md

@@ -18,6 +18,7 @@ As of currently, it packages:
 - Various tools
   - `nix-modrinth-prefetch`
   - `fetchPackwizModpack`
+  - `fetchModrinthModpack`
 
 Check out this video by vimjoyer that provides a brief overview of how to use the flake: https://youtu.be/Fph7SMldxpI
 
@@ -249,6 +250,36 @@ in
 
 **Note**: Using `manifest`, by default, will cause [IFD](https://nixos.wiki/wiki/Import_From_Derivation). If you want to avoid IFD while still having access to `manifest`, simply pass a `manifestHash` to the `fetchPackwizModpack` function, it will then fetch the manifest through `builtins.fetchurl`.
 
+### `fetchModrinthModpack`
+
+[Source](./pkgs/tools/fetchModrinthModpack)
+
+This function packages a Modrinth `.mrpack` modpack from either a URL, a local `.mrpack` file, or a local source directory containing `index.json` and optional overrides.
+
+```nix
+let
+  modpack = pkgs.fetchModrinthModpack {
+    url = "https://cdn.modrinth.com/data/PROJECT_ID/versions/VERSION_ID/modpack.mrpack";
+    packHash = "sha256-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA=";
+    side = "server";
+  };
+in
+{
+  services.minecraft-servers.servers.cool-modpack = {
+    enable = true;
+    package = pkgs.fabricServers.fabric-1_21_5.override { loaderVersion = "0.16.14"; };
+    symlinks = {
+      "mods" = "${modpack}/mods";
+    };
+    files = {
+      "config" = "${modpack}/config";
+    };
+  };
+}
+```
+
+The resulting derivation contains downloaded pack files and applied overrides. Like `fetchPackwizModpack`, it also exposes a `manifest` attribute and an `addFiles` helper.
+
 ### Others
 
 All of these packages are also available under `packages`, not just `legacyPackages`.

pkgs/tools/fetchModrinthModpack/default.nix

@@ -0,0 +1,188 @@
+{
+  lib,
+  stdenvNoCC,
+  jq,
+  moreutils,
+  curl,
+  cacert,
+  unzip,
+  coreutils,
+}:
+
+let
+  fetchModrinthModpack =
+    {
+      # Provide a path to the modpack source directory (containing index.json),
+      # a local .mrpack archive, or a URL to a .mrpack archive.
+      src ? null,
+      url ? null,
+      packHash ? "",
+      # Either 'server', 'client' or 'both' (to get all files)
+      side ? "server",
+      ...
+    }@args:
+    let
+      srcNull = src == null;
+      urlNull = url == null;
+      srcPath = if srcNull then "" else src;
+      urlPath = if urlNull then "" else url;
+      drv = fetchModrinthModpack args;
+    in
+
+    assert lib.assertMsg (
+      srcNull != urlNull # equivalent of (src != null) xor (url != null)
+    ) "Either 'src' or 'url' must be provided to fetchModrinthModpack";
+
+    assert lib.assertMsg (builtins.elem side [
+      "server"
+      "client"
+      "both"
+    ]) "'side' must be one of: server, client, both";
+
+    stdenvNoCC.mkDerivation (
+      {
+        pname = args.pname or "modrinth-pack";
+        version = args.version or "";
+
+        dontUnpack = true;
+
+        buildInputs = [
+          jq
+          moreutils
+          curl
+          cacert
+          unzip
+          coreutils
+        ];
+
+        buildPhase = ''
+          set -euo pipefail
+          runHook preBuild
+
+          mkdir -p pack-src
+
+          if [ "${if !urlNull then "1" else "0"}" = "1" ]; then
+            curl -L "${urlPath}" > modpack.mrpack
+            unzip -q modpack.mrpack -d pack-src
+          elif [ -d "${srcPath}" ]; then
+            cp -r "${srcPath}"/. pack-src/
+          else
+            unzip -q "${srcPath}" -d pack-src
+          fi
+
+          test -f pack-src/index.json
+
+          while IFS= read -r file; do
+            if [ "${side}" != "both" ]; then
+              envState=$(echo "$file" | jq -r --arg side "${side}" '.env[$side] // "required"')
+              if [ "$envState" = "unsupported" ]; then
+                continue
+              fi
+            fi
+
+            path=$(echo "$file" | jq -r '.path')
+            url=$(echo "$file" | jq -r '.downloads[0]')
+            mkdir -p "$(dirname "$path")"
+            curl -L "$url" > "$path"
+
+            if echo "$file" | jq -e '.hashes.sha512 != null' > /dev/null; then
+              expected=$(echo "$file" | jq -r '.hashes.sha512')
+              actual=$(${coreutils}/bin/sha512sum "$path" | cut -d' ' -f1)
+            elif echo "$file" | jq -e '.hashes.sha1 != null' > /dev/null; then
+              expected=$(echo "$file" | jq -r '.hashes.sha1')
+              actual=$(${coreutils}/bin/sha1sum "$path" | cut -d' ' -f1)
+            else
+              echo "No supported hash for '$path' (supported: sha512, sha1)" >&2
+              exit 1
+            fi
+
+            if [ "$actual" != "$expected" ]; then
+              echo "Hash mismatch for '$path'" >&2
+              echo "expected: $expected" >&2
+              echo "actual:   $actual" >&2
+              exit 1
+            fi
+          done < <(jq -c '.files[]' pack-src/index.json)
+
+          if [ -d pack-src/overrides ]; then
+            cp -r pack-src/overrides/. .
+          fi
+
+          if [ "${side}" = "server" ] && [ -d pack-src/server-overrides ]; then
+            cp -r pack-src/server-overrides/. .
+          fi
+
+          if [ "${side}" = "client" ] && [ -d pack-src/client-overrides ]; then
+            cp -r pack-src/client-overrides/. .
+          fi
+
+          if [ "${side}" = "both" ]; then
+            if [ -d pack-src/server-overrides ]; then
+              cp -r pack-src/server-overrides/. .
+            fi
+            if [ -d pack-src/client-overrides ]; then
+              cp -r pack-src/client-overrides/. .
+            fi
+          fi
+
+          # Keep the source manifest in output for passthru consumers.
+          cp pack-src/index.json ./index.json
+
+          runHook postBuild
+        '';
+
+        installPhase = ''
+          runHook preInstall
+
+          # Fix non-determinism
+          rm -rf env-vars
+          jq -Sc '.' index.json | sponge index.json
+
+          mkdir -p "$out"
+          cp * -r "$out/"
+
+          runHook postInstall
+        '';
+
+        passthru = {
+          # Modrinth index manifest as a nix expression.
+          manifest = builtins.fromJSON (builtins.readFile "${drv}/index.json");
+
+          # Adds an attribute set of files to the derivation.
+          # Useful to add server-specific mods not part of the pack.
+          addFiles =
+            files:
+            stdenvNoCC.mkDerivation {
+              inherit (drv) pname version;
+              src = null;
+              dontUnpack = true;
+              dontConfig = true;
+              dontBuild = true;
+              dontFixup = true;
+
+              installPhase = ''
+                cp -as "${drv}" $out
+                chmod u+w -R $out
+              ''
+              + lib.concatLines (
+                lib.mapAttrsToList (name: file: ''
+                  mkdir -p "$out/$(dirname "${name}")"
+                  cp -as "${file}" "$out/${name}"
+                '') files
+              );
+
+              passthru = { inherit (drv) manifest; };
+              meta = drv.meta or { };
+            };
+        };
+
+        dontFixup = true;
+
+        outputHashMode = "recursive";
+        outputHashAlgo = "sha256";
+        outputHash = packHash;
+      }
+      // args
+    );
+in
+fetchModrinthModpack

tests/modrinth-modpack-from-src/default.nix

@@ -0,0 +1,25 @@
+{
+  fetchModrinthModpack,
+  stdenvNoCC,
+}:
+let
+  pack = fetchModrinthModpack {
+    src = ./sample-pack;
+    packHash = "sha256-OAJrZEVTZx1QZe2ubrLfK/XvRusfIN8cWMbj21TYhms=";
+  };
+in
+stdenvNoCC.mkDerivation {
+  name = "modrinth-modpack-from-src-check";
+  doCheck = true;
+  phases = [
+    "checkPhase"
+    "installPhase"
+  ];
+  checkPhase = ''
+    set -euo pipefail
+    test -f '${pack}/index.json'
+    test -f '${pack}/mods/lithium-fabric-0.16.2+mc1.21.5.jar'
+    test -f '${pack}/config/server.properties'
+  '';
+  installPhase = "mkdir $out";
+}

tests/modrinth-modpack-from-src/sample-pack/index.json

@@ -0,0 +1,27 @@
+{
+  "formatVersion": 1,
+  "game": "minecraft",
+  "versionId": "sample-pack-1.0.0",
+  "name": "sample-pack",
+  "summary": "Sample Modrinth modpack for nix-minecraft tests",
+  "files": [
+    {
+      "path": "mods/lithium-fabric-0.16.2+mc1.21.5.jar",
+      "hashes": {
+        "sha512": "09a68051504bb16069dd6af8901f2bbeadfd08ad5353d8bcc0c4784e814fb293d9197b4fb0a8393be1f2db003cd987a9e4b98391bbe18c50ae181dace20c2fa4"
+      },
+      "downloads": [
+        "https://cdn.modrinth.com/data/gvQqBUqZ/versions/VWYoZjBF/lithium-fabric-0.16.2%2Bmc1.21.5.jar"
+      ],
+      "fileSize": 769793,
+      "env": {
+        "client": "required",
+        "server": "required"
+      }
+    }
+  ],
+  "dependencies": {
+    "minecraft": "1.21.5",
+    "fabric-loader": "0.16.14"
+  }
+}

tests/modrinth-modpack-from-src/sample-pack/overrides/config/server.properties

@@ -0,0 +1 @@
+motd=nix-minecraft test