fix: change the preview default mode from development to production

[ygj6]

Description

fix #4007

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[hyf0]

As I describe in #4431, you may also need to set dev always to be true rather config.isProduction.
sirv with dev false seems useless in vite preview.

vite/packages/vite/src/node/preview.ts

Lines 44 to 51 in 690b35e

	app.use(
	config.base,
	sirv(distDir, {
	etag: true,
	dev: !config.isProduction,
	single: true
	})
	)

[hyf0]

Enable "dev" mode, which disables/skips caching. Instead, sirv will traverse the file system on every request.
Additionally, dev mode will ignore maxAge and immutable as these options generate a production-oriented Cache-Control header value. https://github.com/lukeed/sirv/tree/master/packages/sirv#optsdev

I'm not sure to disable sirv dev mode will be good for DX. This will cause if the user uses both yarn build --watch and yarn preview , user have to re-runyarn preview command to refresh server cache to see the newest result.

[ygj6]

The role of preview is to verify the production environment, so we fix the mode to production.
If it is unstable and still under development, is it more appropriate to use vite dev?

[ygj6]

Maybe we can change it to --force, the same as vite dev，is it appropriate?

[patak-dev]

vite preview is not intended to be used for production though, it is just to check locally. So it is fine if the server is in dev mode. We haven't had complaints about this.
There are environments like electron that are using build --watch. The default to me should be dev: true as it was.

[ygj6]

@patak-js
If so, then vite preview is still in development mode by default, but the user is allowed to change the mode by --mode，right?

[hyf0]

vite preview should be in production mode by default to fix the issue you mention. I think only call sirv with dev: true will be ok.

[ygj6]

You are right, mode is really useless in Preview，I have fixed it to production.

[ygj6]

@patak-js @iheyunfei
Thank you, I have modified it, help review.

[sodatea]

Should this line be changed to build too? Because we don't actually need vite server plugins in vite preview.