fix: handle fatal rollup watch events

src/index.ts

@@ -463,8 +463,8 @@ export class Bundler {
       // Since we only output to `.js` now
       // Probably remove it in the future
       .replace(/\[ext\]/, '.js')
- 
-    if (rollupFormat === 'esm')  {
+
+    if (rollupFormat === 'esm') {
       fileName = fileName.replace(/\[format\]/, 'esm')
     }
 
@@ -629,8 +629,9 @@ export class Bundler {
       )
       const watcher = watch(configs)
       watcher.on('event', (e) => {
-        if (e.code === 'ERROR') {
-          logger.error(e.error.message)
+        const code = e.code as string
+        if (code === 'ERROR' || code === 'FATAL') {
+          logger.error((e as { error: Error }).error.message)
         }
       })
     } else {

test/watch.test.ts

@@ -0,0 +1,65 @@
+import { Bundler } from '../src'
+import logger from '../src/logger'
+import { watch } from 'rollup'
+
+jest.mock('rollup', () => ({
+  rollup: jest.fn(),
+  watch: jest.fn(),
+}))
+
+const mockWatch = watch as jest.Mock
+
+describe('watch mode', () => {
+  beforeEach(() => {
+    mockWatch.mockReset()
+    jest.spyOn(logger, 'error').mockImplementation(() => {})
+  })
+
+  afterEach(() => {
+    jest.restoreAllMocks()
+  })
+
+  it('logs fatal Rollup watch events', async () => {
+    const error = new Error('watch failed')
+
+    mockWatch.mockReturnValue({
+      on(event: string, listener: (payload: any) => void) {
+        expect(event).toBe('event')
+        listener({ code: 'FATAL', error })
+      },
+    })
+
+    await new Bundler(
+      { input: 'index.js' },
+      {
+        configFile: false,
+        logLevel: 'quiet',
+        rootDir: __dirname,
+      }
+    ).run({ watch: true })
+
+    expect(logger.error).toHaveBeenCalledWith('watch failed')
+  })
+
+  it('keeps logging normal Rollup watch errors', async () => {
+    const error = new Error('build failed')
+
+    mockWatch.mockReturnValue({
+      on(event: string, listener: (payload: any) => void) {
+        expect(event).toBe('event')
+        listener({ code: 'ERROR', error })
+      },
+    })
+
+    await new Bundler(
+      { input: 'index.js' },
+      {
+        configFile: false,
+        logLevel: 'quiet',
+        rootDir: __dirname,
+      }
+    ).run({ watch: true })
+
+    expect(logger.error).toHaveBeenCalledWith('build failed')
+  })
+})