fix: incorrect default export in CJS output

Author: JasonWeinzierl

build.config.ts

@@ -1,12 +1,12 @@
 import { defineBuildConfig } from 'unbuild';
 
 export default defineBuildConfig({
-    entries: [
-        'src/index',
-    ],
-    declaration: true,
-    clean: true,
-    rollup: {
-        emitCJS: true,
-    },
+  entries: [
+    'src/index',
+  ],
+  declaration: true,
+  clean: true,
+  rollup: {
+    emitCJS: true,
+  },
 });

package.json

@@ -41,7 +41,7 @@
     "docs"
   ],
   "scripts": {
-    "build": "unbuild",
+    "build": "unbuild && tsx scripts/postbuild.ts",
     "lint": "eslint",
     "release": "bumpp && yarn run build",
     "test": "vitest",
@@ -76,6 +76,7 @@
     "eslint-plugin-import-x": "^4.4.0",
     "eslint-plugin-n": "^17.12.0",
     "rxjs": "^7.0.0",
+    "tsx": "^4.19.2",
     "typescript": "~5.6.3",
     "typescript-eslint": "^8.12.2",
     "unbuild": "^2.0.0",

scripts/postbuild.ts

@@ -0,0 +1,22 @@
+/**
+ * There is known issue with unbuild CJS bundling: https://github.com/unjs/unbuild/issues/374
+ *
+ * Script from https://github.com/antfu-collective/vite-plugin-inspect/blob/main/scripts/postbuild.ts
+ *
+ * Explanation of problem: https://github.com/arethetypeswrong/arethetypeswrong.github.io/blob/main/docs/problems/FalseExportDefault.md
+ */
+import { readFileSync, writeFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+
+function patchCjs(cjsModulePath: string, name: string) {
+  const cjsModule = readFileSync(cjsModulePath, 'utf-8')
+  writeFileSync(
+    cjsModulePath,
+    cjsModule
+      .replace(`'use strict';`, `'use strict';Object.defineProperty(exports, '__esModule', {value: true});`)
+      .replace(`module.exports = ${name};`, `exports.default = ${name};`),
+    { encoding: 'utf-8' },
+  )
+}
+
+patchCjs(resolve('./dist/index.cjs'), 'rxjsX')