build(rrweb): generate record declarations with Oxc

packages/rrweb/record/package.json

@@ -7,10 +7,11 @@
     "scripts": {
         "dev": "vite build --watch",
         "build": "pnpm turbo run prepublish",
+        "build:declarations": "rolldown -c rolldown.dts.config.mts",
         "test": "vitest run",
         "test:watch": "vitest watch",
         "check-types": "tsc -noEmit",
-        "prepublish": "tsc -noEmit && vite build",
+        "prepublish": "tsc -noEmit && vite build && pnpm build:declarations",
         "lint": "oxlint src"
     },
     "repository": {
@@ -41,6 +42,8 @@
     ],
     "devDependencies": {
         "puppeteer": "^23.11.1",
+        "rolldown": "catalog:",
+        "rolldown-plugin-dts": "catalog:",
         "vite": "catalog:",
         "vite-plugin-dts": "catalog:",
         "vitest": "^1.4.0",

packages/rrweb/record/rolldown.dts.config.mts

@@ -0,0 +1,32 @@
+import { copyFileSync } from 'node:fs';
+import path from 'node:path';
+import { defineConfig, type Plugin } from 'rolldown';
+import { dts } from 'rolldown-plugin-dts';
+
+function copyDeclarationsForCommonJs(): Plugin {
+  return {
+    name: 'copy-declarations-for-commonjs',
+    writeBundle(outputOptions) {
+      if (!outputOptions.dir) return;
+
+      const declarationPath = path.resolve(outputOptions.dir, 'index.d.ts');
+      copyFileSync(declarationPath, declarationPath.replace(/\.d\.ts$/, '.d.cts'));
+    },
+  };
+}
+
+export default defineConfig({
+  input: 'src/index.ts',
+  external: ['@posthog/rrweb'],
+  output: {
+    dir: 'dist',
+    format: 'es',
+  },
+  plugins: [
+    ...dts({
+      emitDtsOnly: true,
+      generator: 'oxc',
+    }),
+    copyDeclarationsForCommonJs(),
+  ],
+});

packages/rrweb/record/test/build-output.test.ts

@@ -9,4 +9,26 @@ describe('build output', () => {
         expect(bundle).not.toContain('sourceMappingURL=image-bitmap-data-url-worker-')
         expect(bundle).toContain('sourceMappingURL=rrweb-record.js.map')
     })
+
+    it('emits matching ESM and CommonJS declarations', () => {
+        const esmDeclarations = readFileSync(resolve(__dirname, '../dist/index.d.ts'), 'utf8')
+        const commonJsDeclarations = readFileSync(resolve(__dirname, '../dist/index.d.cts'), 'utf8')
+
+        const expectedExports = [
+            'DeferredStylesheetStats',
+            'MutationCost',
+            'SnapshotCost',
+            'getDeferredStylesheetStats',
+            'getDiscardedDurationSamples',
+            'getLastSnapshotCost',
+            'getMutationCost',
+            'record',
+            'resetMaxDepthState',
+            'resetSnapshotCostState',
+            'wasMaxDepthReached',
+        ]
+
+        expect(commonJsDeclarations).toBe(esmDeclarations)
+        expectedExports.forEach((exportName) => expect(esmDeclarations).toContain(exportName))
+    })
 })

packages/rrweb/record/tsconfig.json

@@ -5,7 +5,8 @@
   ],
   "compilerOptions": {
     "rootDir": "src",
-    "tsBuildInfoFile": "./tsconfig.tsbuildinfo"
+    "tsBuildInfoFile": "./tsconfig.tsbuildinfo",
+    "isolatedDeclarations": true
   },
   "references": [
     {

packages/rrweb/record/vite.config.ts

@@ -11,6 +11,7 @@ const workspacePackages: Record<string, string> = {
 };
 
 export default config(path.resolve(__dirname, 'src/index.ts'), 'rrweb', {
+  generateDeclarations: process.argv.includes('--watch'),
   plugins: [
     {
       name: 'resolve-workspace-sources',