👷 Create an ESM build with Rollup by renaming output files with .esm

client/package.json

@@ -1,5 +1,6 @@
 {
   "internal": true,
   "main": "../dist/client/index.js",
+  "module": "../dist/client/index.esm.js",
   "types": "../dist/client/index.d.ts"
 }

package.json

@@ -3,6 +3,7 @@
   "version": "0.3.6",
   "description": "Authentication library for use with SvelteKit featuring built-in OAuth providers and zero restriction customization!",
   "main": "dist/index.js",
+  "module": "dist/index.esm.js",
   "types": "dist/index.d.ts",
   "exports": {
     ".": "./dist/index.js",

providers/package.json

@@ -1,5 +1,6 @@
 {
   "internal": true,
   "main": "../dist/providers/index.js",
+  "module": "../dist/providers/index.esm.js",
   "types": "../dist/providers/index.d.ts"
 }

rollup.config.js

@@ -8,17 +8,15 @@ const globals = {
   ...packageJson.devDependencies,
 };
 
-export default [
-  {
+/** @type {import('rollup').RollupOptions} */
+const baseConfig = {
   input: ["src/**/*.ts"],
   output: {
     dir: "dist",
     sourcemap: true,
-      format: "cjs",
   },
   plugins: [
     esbuild(),
-      multiInput(),
     typescript({
       emitDeclarationOnly: true,
       sourceMap: false,
@@ -29,5 +27,31 @@ export default [
     "@sveltejs/kit/assets/runtime/app/navigation",
     "@sveltejs/kit/assets/runtime/app/stores",
   ],
+};
+
+/** @type {Array.<import('rollup').RollupOptions>} */
+export default [
+  {
+    ...baseConfig,
+    output: {
+      ...baseConfig.output,
+      format: "cjs",
+    },
+    plugins: [...baseConfig.plugins, multiInput()],
+  },
+  {
+    ...baseConfig,
+    output: {
+      ...baseConfig.output,
+      format: "esm",
+    },
+    plugins: [
+      ...baseConfig.plugins,
+      multiInput({
+        /** @param {string} output */
+        transformOutputPath: (output) =>
+          `${output.split(".").slice(0, -1).join(".")}.esm.${output.split(".").slice(-1)}`,
+      }),
+    ],
   },
 ];