nix: write prisma-language-server derivation (#1313)

That makes it very easy for nix users to reproducibly build and run the
language server. See the new section in CONTRIBUTING.md for more info.

Good next steps would be integrating test runs and improving the dev
shell.

Author: tomhoule

.gitignore

@@ -10,6 +10,9 @@ coverage
 # Dependency directory
 **/node_modules/**
 
+# Nix
+/result
+
 # Others
 /.direnv
 dist/

flake.lock

@@ -7,16 +7,29 @@
       inputs.nixpkgs-lib.follows = "nixpkgs";
     };
     nixpkgs.url = "nixpkgs/nixos-unstable";
+    dream2nix = {
+      url = "github:nix-community/dream2nix";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-parts.follows = "flake-parts";
+
+        # Avoid fetching large unused projects.
+        all-cabal-json.follows = "nixpkgs";
+        nix-pypi-fetcher.follows = "nixpkgs";
+      };
+    };
   };
 
-  outputs = { self, nixpkgs, flake-parts }:
+  outputs = { self, nixpkgs, flake-parts, dream2nix }:
     flake-parts.lib.mkFlake { inherit self; } {
       systems = [ "x86_64-linux" ];
-      perSystem = { pkgs, system, self', ... }:
+      imports = [ dream2nix.flakeModuleBeta ];
+      perSystem = { ... }:
         {
           imports = [
-            ./nix/format-project.nix
             ./nix/delete-node-modules.nix
+            ./nix/format-project.nix
+            ./nix/prisma-language-server.nix
             ./nix/shell.nix
             ./nix/vscode.nix
           ];

flake.nix

@@ -3,7 +3,7 @@
 {
   packages.formatProject = pkgs.writeShellScriptBin "formatProject" ''
     PATH=${pkgs.nodejs}/bin:${pkgs.jq}/bin:$PATH
-    PRETTIER_VERSION=`jq -r .devDependencies.prettier ${./package.json}`
+    PRETTIER_VERSION=`jq -r .devDependencies.prettier ${../package.json}`
     npx prettier@$PRETTIER_VERSION -w ./packages/**/*.ts ./**/*.json ./**/*.js
   '';
 }

nix/format-project.nix

@@ -0,0 +1,44 @@
+{ pkgs, config, ... }:
+
+let
+  # We clean up the source for dream2nix to produce just the node_modules we
+  # need to build and run the server.
+  src = pkgs.runCommand "makesrc"
+    { jq = pkgs.jq; root = ../packages/language-server; }
+    ''
+      export PATH="$jq/bin:$PATH"
+
+      mkdir $out
+      cp -r $root/src $out/src
+      cp $root/package-lock.json $out/package-lock.json
+      jq 'del(.scripts) | del(.bin) | del(.devDependencies.typescript) | del(.devDependencies.mocha)' $root/package.json > $out/package.json
+      jq 'del(.extends) | del(.exclude)' $root/tsconfig.json > $out/tsconfig.json
+    '';
+
+  inherit (pkgs) nodejs typescript;
+in
+{
+  dream2nix.inputs.language-server.source = src;
+
+  packages.prisma-language-server =
+    let nodeDeps = config.dream2nix.outputs.language-server.packages."@prisma/language-server"; in
+    pkgs.stdenv.mkDerivation
+      {
+        name = "prisma-language-server";
+        src = "${nodeDeps}/lib/node_modules/@prisma/language-server";
+
+        buildInputs = [ nodejs typescript ];
+        buildPhase = ''
+          tsc --outDir $out/lib/dist
+          cp -r node_modules $out/lib
+          cp package.json $out/lib
+        '';
+
+        installPhase = ''
+          mkdir $out/bin
+          echo '#!/bin/bash' >> $out/bin/prisma-language-server
+          echo "${nodejs}/bin/node $out/lib/dist/src/bin.js" >> $out/bin/prisma-language-server
+          chmod +x $out/bin/prisma-language-server
+        '';
+      };
+}

nix/prisma-language-server.nix

@@ -4,6 +4,7 @@
   devShells.default = pkgs.mkShell {
     packages = [
       pkgs.nodejs
+      pkgs.typescript
       self'.packages.buildVscodeExtension
       self'.packages.code
       self'.packages.deleteNodeModules

nix/shell.nix

@@ -25,3 +25,13 @@ Unit tests:
 ## Publishing
 
 The extension is automatically published to npm via GitHub actions (see `.github/workflows`).
+
+## Nix users
+
+The flake in this repository has a language server package.
+
+Run `nix build .#prisma-language-server` to build it. The compiled output and a
+wrapper script will be in the `result/` directory.
+
+Run `nix run .#prisma-language-server -- --stdio` to run the language server, listening
+over stdio.