Allow disabling watcher altogether

[sheremet-va]

Description

When calling createServer, vite always starts a watcher however it is not always necessary if the consumer just wants to use transformRequest API. For example, when running Vitest with --run or --no-watch command we don't need a watcher and currently set ignored to ['**/*'] to lower the memory consumption. But it seems that it's not enough because Vite adds new files to watch manually (like tsconfig).

Suggested solution

Allow passing down false as an option to server.watch:

import { defineConfig } from 'vite'
export default defineConfig({
  server: {
    watch: false
  }
})

Instead of starting a chokidar service, Vite will create a noop watcher to not break the API.

Alternative

No response

Additional context

No response

Validations

• Follow our Code of Conduct
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[AriPerkkio]

While working on vitest-dev/vitest#3925 I noticed that sometimes Chokidar can prevent Vitest process from exiting gracefully. By using why-is-node-running to debug the process, it pointed to Vite's Chokidar usage:

# fsevents
node:internal/async_hooks:202                                                                                                          
/Users/x/y/vitest/node_modules/.pnpm/fsevents@2.3.2/node_modules/fsevents/fsevents.js:31                                            - let instance = Native.start(Native.global, path, since, handler);
file:///Users/x/y/vitest/node_modules/.pnpm/vite@4.3.9_@types+node@18.7.13/node_modules/vite/dist/node/chunks/dep-e8f070e8.js:51089
file:///Users/x/y/vitest/node_modules/.pnpm/vite@4.3.9_@types+node@18.7.13/node_modules/vite/dist/node/chunks/dep-e8f070e8.js:51145
file:///Users/x/y/vitest/node_modules/.pnpm/vite@4.3.9_@types+node@18.7.13/node_modules/vite/dist/node/chunks/dep-e8f070e8.js:51348
file:///Users/x/y/vitest/node_modules/.pnpm/vite@4.3.9_@types+node@18.7.13/node_modules/vite/dist/node/chunks/dep-e8f070e8.js:51424
file:///Users/x/y/vitest/node_modules/.pnpm/vite@4.3.9_@types+node@18.7.13/node_modules/vite/dist/node/chunks/dep-e8f070e8.js:51513
node:internal/process/task_queues:95                                                                                                   

When the process was hanging and required forceful exit, it would leave a zombie process on the background. This process started to eat memory really fast and eventually caused out-of-memory from Node's side. This process is shown on the video below.

chokidarvitest.mp4

After patching Vite by modifying node_modules/ directly with following changes, the process hangs disappeared immediately and background zombie processes were gone.

+    const watcher =  { close: () => {}, on: () => { return watcher }, add: () => {} }
-    const watcher = chokidar.watch(
-    // config file dependencies and env file might be outside of root
-    [root, ...config.configFileDependencies, config.envDir], resolvedWatchOptions);

vite/packages/vite/src/node/server/index.ts

Lines 362 to 366 in fe1c0b9

	const watcher = chokidar.watch(
	// config file dependencies and env file might be outside of root
	[root, ...config.configFileDependencies, config.envDir],
	resolvedWatchOptions,
	) as FSWatcher