Add some settings

README.md

@@ -7,8 +7,13 @@ Generates a Nix expression to build a Yarn v2 project (not using zero-install).
 ## Usage
 
 ```sh
+# Install the plugin.
 yarn plugin import https://raw.githubusercontent.com/stephank/yarn-plugin-nixify/main/dist/yarn-plugin-nixify.js
+
+# Run Yarn as usual.
 yarn
+
+# Build your project with Nix.
 nix-build
 ```
 
@@ -33,12 +38,7 @@ Some examples of how to customize your build from within `default.nix`:
 let
 
   # Example of providing a different source.
-  src = fetchFromGitHub {
+  src = pkgs.lib.cleanSource ./.;
-    owner = "johndoe";
-    repo = "myproject";
-    rev = "v1.0.0";
-    sha256 = "1hdhafj726g45gh7nj8qv1xls8mps3vhzq3aasdymbdqcb1clhkz";
-  };
 
   project = pkgs.callPackage ./yarn-project.nix {
 
@@ -49,9 +49,12 @@ let
 
 in project.overrideAttrs (oldAttrs: {
 
+  # If your top-level package.json doesn't set a name, you can set one here.
+  name = "myproject";
+
   # Example of adding dependencies to the environment.
   # Native modules sometimes need these to build.
-  buildInputs = oldAttrs.buildInputs ++ [ python3 ];
+  buildInputs = oldAttrs.buildInputs ++ [ pkgs.python3 ];
 
   # Example of invoking a build step in your project.
   buildPhase = ''

src/generate.ts

@@ -103,10 +103,10 @@ export default async (project: Project, cache: Cache, report: Report) => {
           .join(``) +
         `  ]`
     );
-  const projectExprPath = ppath.join(cwd, `yarn-project.nix` as Filename);
+  xfs.writeFileSync(configuration.get(`nixExprPath`), projectExpr);
-  xfs.writeFileSync(projectExprPath, projectExpr);
 
   // Create a wrapper if it does not exist yet.
+  if (configuration.get(`generateDefaultNix`)) {
     const defaultExprPath = ppath.join(cwd, `default.nix` as Filename);
     if (!xfs.existsSync(defaultExprPath)) {
       xfs.writeFileSync(defaultExprPath, defaultExprTmpl);
@@ -115,10 +115,14 @@ export default async (project: Project, cache: Cache, report: Report) => {
         `A minimal default.nix was created. You may want to customize it.`
       );
     }
+  }
 
   // Preload the cache entries into the Nix store.
-  if (xfs.existsSync(npath.toPortablePath(`/nix/store`))) {
+  if (
-    xfs.mktempPromise(async (tempDir) => {
+    configuration.get(`enableNixPreload`) &&
+    xfs.existsSync(npath.toPortablePath(`/nix/store`))
+  ) {
+    await xfs.mktempPromise(async (tempDir) => {
       const toPreload: PortablePath[] = [];
       for (const { name, filename, sha512 } of cacheEntries) {
         // Check to see if the Nix store entry already exists.

src/index.ts

@@ -1,17 +1,42 @@
 import FetchOneCommand from "./FetchOneCommand";
 import InstallBinCommand from "./InstallBinCommand";
 import generate from "./generate";
-import { Hooks, Plugin } from "@yarnpkg/core";
+import { Hooks, Plugin, SettingsType } from "@yarnpkg/core";
 
 const plugin: Plugin<Hooks> = {
   commands: [FetchOneCommand, InstallBinCommand],
   hooks: {
     afterAllInstalled: async (project, opts) => {
-      if (opts.persistProject !== false) {
+      if (
+        opts.persistProject !== false &&
+        project.configuration.get(`enableNixify`)
+      ) {
         await generate(project, opts.cache, opts.report);
       }
     },
   },
+  configuration: {
+    enableNixify: {
+      description: `If false, disables the Nixify plugin hook that generates Nix expressions`,
+      type: SettingsType.BOOLEAN,
+      default: true,
+    },
+    nixExprPath: {
+      description: `Path of the file where the project Nix expression will be written to`,
+      type: SettingsType.ABSOLUTE_PATH,
+      default: `./yarn-project.nix`,
+    },
+    generateDefaultNix: {
+      description: `If true, a default.nix will be generated if it does not exist`,
+      type: SettingsType.BOOLEAN,
+      default: true,
+    },
+    enableNixPreload: {
+      description: `If true, cached packages will be preloaded into the Nix store`,
+      type: SettingsType.BOOLEAN,
+      default: true,
+    },
+  },
 };
 
 export default plugin;

src/tmpl/yarn-project.nix.in

@@ -36,6 +36,8 @@ in stdenv.mkDerivation {
   name = @@PROJECT_NAME@@;
   inherit src;
 
+  # Disable Nixify plugin to save on some unnecessary processing.
+  yarn_enable_nixify = "false";
   # Tell node-gyp to use the provided Node.js headers for native code builds.
   npm_config_nodedir = nodejs;
   # Tell node-pre-gyp to never fetch binaries / always build from source.