Configure Rollup build with Babel

Author: colinrotherham

package.json

@@ -63,6 +63,7 @@
     "@babel/preset-env": "^7.28.3",
     "@babel/preset-react": "^7.27.1",
     "@babel/preset-typescript": "^7.27.1",
+    "@rollup/plugin-babel": "^6.0.4",
     "@rollup/plugin-commonjs": "^28.0.6",
     "@rollup/plugin-node-resolve": "^16.0.1",
     "@rollup/plugin-typescript": "^12.1.4",
@@ -88,6 +89,7 @@
     "babel-jest": "^29.7.0",
     "babel-plugin-module-resolver": "^5.0.2",
     "chromatic": "^6.17.3",
+    "classnames": "^2.5.1",
     "eslint": "^8.57.0",
     "eslint-config-airbnb": "^19.0.4",
     "eslint-config-prettier": "^9.1.0",
@@ -109,17 +111,17 @@
     "rollup": "^4.52.4",
     "sass": "^1.53.0",
     "storybook": "^8.0.5",
+    "tslib": "^2.8.1",
     "typescript": "5.3.3",
     "vite": "^4.5.3",
     "vite-tsconfig-paths": "^4.3.2"
   },
-  "dependencies": {
-    "classnames": "^2.2.6"
-  },
   "peerDependencies": {
+    "classnames": ">=2.5.0",
     "nhsuk-frontend": ">=10.0.0 <11.0.0",
     "react": ">=16.8.0",
-    "react-dom": ">=16.8.0"
+    "react-dom": ">=16.8.0",
+    "tslib": ">=2.8.0"
   },
   "packageManager": "[email protected]"
 }

rollup.config.mjs

@@ -1,4 +1,5 @@
 import { join } from 'node:path';
+import { babel } from '@rollup/plugin-babel';
 import commonjs from '@rollup/plugin-commonjs';
 import { nodeResolve } from '@rollup/plugin-node-resolve';
 import typescript from '@rollup/plugin-typescript';
@@ -28,14 +29,20 @@ export default defineConfig(
       ],
       external,
       plugins: [
-        nodeResolve(),
+        nodeResolve({
+          browser: true,
+        }),
         commonjs(),
         typescript({
           tsconfig: 'tsconfig.build.json',
           compilerOptions: {
             outDir: join(outDir, format),
           },
         }),
+        babel({
+          babelHelpers: 'bundled',
+          exclude: 'node_modules/**',
+        }),
       ],
 
       // Handle warnings as errors

yarn.lock

@@ -343,16 +343,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"@babel/helper-module-imports@npm:^7.22.15, @babel/helper-module-imports@npm:^7.24.1":
-  version: 7.24.3
-  resolution: "@babel/helper-module-imports@npm:7.24.3"
-  dependencies:
-    "@babel/types": "npm:^7.24.0"
-  checksum: 10c0/052c188adcd100f5e8b6ff0c9643ddaabc58b6700d3bbbc26804141ad68375a9f97d9d173658d373d31853019e65f62610239e3295cdd58e573bdcb2fded188d
-  languageName: node
-  linkType: hard
-
-"@babel/helper-module-imports@npm:^7.27.1":
+"@babel/helper-module-imports@npm:^7.18.6, @babel/helper-module-imports@npm:^7.27.1":
   version: 7.27.1
   resolution: "@babel/helper-module-imports@npm:7.27.1"
   dependencies:
@@ -362,6 +353,15 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@babel/helper-module-imports@npm:^7.22.15, @babel/helper-module-imports@npm:^7.24.1":
+  version: 7.24.3
+  resolution: "@babel/helper-module-imports@npm:7.24.3"
+  dependencies:
+    "@babel/types": "npm:^7.24.0"
+  checksum: 10c0/052c188adcd100f5e8b6ff0c9643ddaabc58b6700d3bbbc26804141ad68375a9f97d9d173658d373d31853019e65f62610239e3295cdd58e573bdcb2fded188d
+  languageName: node
+  linkType: hard
+
 "@babel/helper-module-transforms@npm:^7.23.3":
   version: 7.23.3
   resolution: "@babel/helper-module-transforms@npm:7.23.3"
@@ -3555,6 +3555,25 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@rollup/plugin-babel@npm:^6.0.4":
+  version: 6.0.4
+  resolution: "@rollup/plugin-babel@npm:6.0.4"
+  dependencies:
+    "@babel/helper-module-imports": "npm:^7.18.6"
+    "@rollup/pluginutils": "npm:^5.0.1"
+  peerDependencies:
+    "@babel/core": ^7.0.0
+    "@types/babel__core": ^7.1.9
+    rollup: ^1.20.0||^2.0.0||^3.0.0||^4.0.0
+  peerDependenciesMeta:
+    "@types/babel__core":
+      optional: true
+    rollup:
+      optional: true
+  checksum: 10c0/5a7c04fa6d608512b597835e749aef33e129ee9ed6cc9e33489b7d43937358fc8aba48b00819604d0bc9b7c20790a6c035e4136e8d9f70cf0d0f056ba547e700
+  languageName: node
+  linkType: hard
+
 "@rollup/plugin-commonjs@npm:^28.0.6":
   version: 28.0.6
   resolution: "@rollup/plugin-commonjs@npm:28.0.6"
@@ -6210,7 +6229,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"classnames@npm:^2.2.6":
+"classnames@npm:^2.5.1":
   version: 2.5.1
   resolution: "classnames@npm:2.5.1"
   checksum: 10c0/afff4f77e62cea2d79c39962980bf316bacb0d7c49e13a21adaadb9221e1c6b9d3cdb829d8bb1b23c406f4e740507f37e1dcf506f7e3b7113d17c5bab787aa69
@@ -10639,6 +10658,7 @@ __metadata:
     "@babel/preset-env": "npm:^7.28.3"
     "@babel/preset-react": "npm:^7.27.1"
     "@babel/preset-typescript": "npm:^7.27.1"
+    "@rollup/plugin-babel": "npm:^6.0.4"
     "@rollup/plugin-commonjs": "npm:^28.0.6"
     "@rollup/plugin-node-resolve": "npm:^16.0.1"
     "@rollup/plugin-typescript": "npm:^12.1.4"
@@ -10664,7 +10684,7 @@ __metadata:
     babel-jest: "npm:^29.7.0"
     babel-plugin-module-resolver: "npm:^5.0.2"
     chromatic: "npm:^6.17.3"
-    classnames: "npm:^2.2.6"
+    classnames: "npm:^2.5.1"
     eslint: "npm:^8.57.0"
     eslint-config-airbnb: "npm:^19.0.4"
     eslint-config-prettier: "npm:^9.1.0"
@@ -10686,13 +10706,16 @@ __metadata:
     rollup: "npm:^4.52.4"
     sass: "npm:^1.53.0"
     storybook: "npm:^8.0.5"
+    tslib: "npm:^2.8.1"
     typescript: "npm:5.3.3"
     vite: "npm:^4.5.3"
     vite-tsconfig-paths: "npm:^4.3.2"
   peerDependencies:
+    classnames: ">=2.5.0"
     nhsuk-frontend: ">=10.0.0 <11.0.0"
     react: ">=16.8.0"
     react-dom: ">=16.8.0"
+    tslib: ">=2.8.0"
   languageName: unknown
   linkType: soft
 
@@ -13080,6 +13103,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"tslib@npm:^2.8.1":
+  version: 2.8.1
+  resolution: "tslib@npm:2.8.1"
+  checksum: 10c0/9c4759110a19c53f992d9aae23aac5ced636e99887b51b9e61def52611732872ff7668757d4e4c61f19691e36f4da981cd9485e869b4a7408d689f6bf1f14e62
+  languageName: node
+  linkType: hard
+
 "type-check@npm:^0.4.0, type-check@npm:~0.4.0":
   version: 0.4.0
   resolution: "type-check@npm:0.4.0"