Add bundle-size script (#455)

Author: charpeni

package.json

@@ -23,7 +23,8 @@
   "scripts": {
     "test": "jest",
     "lint": "eslint .",
-    "prepare": "husky install"
+    "prepare": "husky install",
+    "bundle-size": "node scripts/bundle-size"
   },
   "author": "Nicolas Charpentier <[email protected]>",
   "license": "MIT",
@@ -39,9 +40,11 @@
     "jest": "29.5.0",
     "lint-staged": "13.2.3",
     "metro-react-native-babel-preset": "0.76.7",
+    "nanoid": "3.3.6",
     "prettier": "2.8.8",
     "react": "18.2.0",
     "react-native": "0.72.1",
+    "react-native-bundle-scale": "1.1.0",
     "typescript": "5.1.6"
   },
   "peerDependencies": {

scripts/bundle-size.js

@@ -0,0 +1,39 @@
+#!/usr/bin/node
+const util = require('node:util');
+const exec = util.promisify(require('node:child_process').exec);
+const {spawn} = require('node:child_process');
+const fs = require('node:fs');
+const {nanoid} = require('nanoid');
+
+const {name, version} = require('../package.json');
+
+/**
+ * We can't simply provide the generated tarball to `react-native-bundle-scale`, because
+ * Yarn will cache it based on the name of the tarball, and subsequent runs of this script
+ * will always result in the same output even though the content may have changed.
+ *
+ * That's why we need to rename the tarball with something unique.
+ */
+(async () => {
+  await exec('npm pack');
+
+  const tarballName = `${name}-${nanoid()}`;
+  await exec(`mv ${name}-${version}.tgz ${tarballName}.tgz`);
+
+  const childProcess = spawn(
+    'npx',
+    [
+      'react-native-bundle-scale',
+      JSON.stringify({
+        'react-native-url-polyfill': `file:${__dirname}/../${tarballName}.tgz`,
+      }),
+      '--packages-as-json',
+      '--debug',
+    ],
+    {stdio: 'inherit'},
+  );
+
+  childProcess.on('close', () => {
+    fs.unlinkSync(`${tarballName}.tgz`);
+  });
+})();