fix(build): watch publicDir files in build watch mode

packages/vite/src/node/plugins/prepareOutDir.ts

@@ -5,13 +5,44 @@ import colors from 'picocolors'
 import type { Plugin } from '../plugin'
 import { getResolvedOutDirs, resolveEmptyOutDir } from '../watch'
 import type { Environment } from '../environment'
-import { copyDir, emptyDir, normalizePath } from '../utils'
+import {
+  ERR_SYMLINK_IN_RECURSIVE_READDIR,
+  copyDir,
+  emptyDir,
+  normalizePath,
+  recursiveReaddir,
+} from '../utils'
 import { withTrailingSlash } from '../../shared/utils'
 
 export function prepareOutDirPlugin(): Plugin {
   const rendered = new Set<Environment>()
   return {
     name: 'vite:prepare-out-dir',
+    async buildStart() {
+      const { build: options, publicDir } = this.environment.config
+      if (
+        !options.watch ||
+        !options.write ||
+        !options.copyPublicDir ||
+        !publicDir
+      ) {
+        return
+      }
+      // Public files bypass the bundler, so nothing else adds them to the
+      // watch set. A rebuild re-copies them in `renderStart` below.
+      let publicFiles: string[]
+      try {
+        publicFiles = await recursiveReaddir(publicDir)
+      } catch (e) {
+        if (e.code === ERR_SYMLINK_IN_RECURSIVE_READDIR) {
+          return
+        }
+        throw e
+      }
+      for (const file of publicFiles) {
+        this.addWatchFile(file)
+      }
+    },
     watchChange() {
       rendered.delete(this.environment)
     },

playground/assets/__tests__/assets.spec.ts

@@ -1,3 +1,4 @@
+import { existsSync } from 'node:fs'
 import path from 'node:path'
 import { describe, expect, test } from 'vitest'
 import {
@@ -15,7 +16,9 @@ import {
   page,
   readFile,
   readManifest,
+  removeFile,
   serverLogs,
+  testDir,
   viteTestUrl,
   watcher,
 } from '~utils'
@@ -811,6 +814,21 @@ describe.runIf(isBuild)('css and assets in css in build watch', () => {
     await page.reload()
     expect(await page.textContent('.raw-query')).toBe('zoo2')
   })
+
+  // `static/bar` is not imported anywhere, so it only reaches outDir if
+  // publicDir itself is watched
+  test('editing a file in publicDir updates outDir', async () => {
+    expect(readFile('dist/foo/bar')).toBe('bar\n')
+    editFile('static/bar', (code) => code.replace('bar', 'bar2'))
+    await notifyRebuildComplete(watcher)
+    expect(readFile('dist/foo/bar')).toBe('bar2\n')
+  })
+
+  test('removing a file from publicDir updates outDir', async () => {
+    removeFile('static/bar')
+    await notifyRebuildComplete(watcher)
+    expect(existsSync(path.resolve(testDir, 'dist/foo/bar'))).toBe(false)
+  })
 })
 
 test('inline style test', async () => {