fix(bundling): support exported array of options for rollup (#22703)

e2e/rollup/src/rollup.test.ts

@@ -210,4 +210,30 @@ export default config;
     checkFilesExist(`libs/test/dist/bundle.js`);
     checkFilesExist(`libs/test/dist/bundle.es.js`);
   });
+
+  it('should support array config from rollup.config.js', () => {
+    const jsLib = uniq('jslib');
+    runCLI(`generate @nx/js:lib ${jsLib} --bundler rollup`);
+    updateFile(
+      `libs/${jsLib}/rollup.config.js`,
+      `module.exports = (config) => [{
+        ...config,
+        output: {
+          format: "esm",
+          dir: "dist/test",
+          name: "Mylib",
+          entryFileNames: "[name].js",
+          chunkFileNames: "[name].js"
+        }
+      }]`
+    );
+    updateJson(join('libs', jsLib, 'project.json'), (config) => {
+      config.targets.build.options.rollupConfig = `libs/${jsLib}/rollup.config.js`;
+      return config;
+    });
+
+    expect(() => runCLI(`build ${jsLib} --format=esm`)).not.toThrow();
+
+    checkFilesExist(`dist/test/index.js`);
+  });
 });

packages/rollup/src/executors/rollup/rollup.impl.ts

@@ -118,14 +118,18 @@ export async function* rollupExecutor(
       }
 
       const start = process.hrtime.bigint();
-      const bundle = await rollup.rollup(rollupOptions);
+      const allRollupOptions = Array.isArray(rollupOptions)
-      const output = Array.isArray(rollupOptions.output)
+        ? rollupOptions
-        ? rollupOptions.output
+        : [rollupOptions];
-        : [rollupOptions.output];
+
+      for (const opts of allRollupOptions) {
+        const bundle = await rollup.rollup(opts);
+        const output = Array.isArray(opts.output) ? opts.output : [opts.output];
 
         for (const o of output) {
           await bundle.write(o);
         }
+      }
 
       const end = process.hrtime.bigint();
       const duration = `${(Number(end - start) / 1_000_000_000).toFixed(2)}s`;
@@ -150,7 +154,7 @@ export async function createRollupOptions(
   packageJson: PackageJson,
   sourceRoot: string,
   npmDeps: string[]
-): Promise<rollup.RollupOptions> {
+): Promise<rollup.RollupOptions | rollup.RollupOptions[]> {
   const useBabel = options.compiler === 'babel';
   const useTsc = options.compiler === 'tsc';
   const useSwc = options.compiler === 'swc';
@@ -287,7 +291,7 @@ export async function createRollupOptions(
   const userDefinedRollupConfigs = options.rollupConfig.map((plugin) =>
     loadConfigFile(plugin)
   );
-  let finalConfig: rollup.InputOptions = rollupConfig;
+  let finalConfig: rollup.RollupOptions = rollupConfig;
   for (const _config of userDefinedRollupConfigs) {
     const config = await _config;
     if (typeof config === 'function') {