feat!: appType (spa, mpa, custom), boolean middlewareMode

[patak-dev]

Description

Close #8438

Context:

• fix: dont remove indexHtmlMiddleware when spa false #8438
• feat: spa option, preview and dev for MPA and SSR apps #8217

This PR implements:

Current	Proposed
server mode	appType: 'spa' | 'mpa' | 'custom'
server.middlewareMode: 'ssr'	appType: 'custom' + server.middlewareMode: true
server.middlewareMode: 'html'	appType: 'spa' | 'mpa' + server.middlewareMode: true

server.middlewareMode was originally a boolean and we extended it to be 'ssr' | 'html' once people wanted control over the included middlewares.

#8217 introduced a spa: boolean option, but we found out while discussing in #8438 that it isn't enough and that there is overlap between this new option and the extensions previously added to middlewareMode

This PR reverts middlewareMode to a boolean, that now only controls if there is a server managed by Vite and has no effect on what middlewares are included. A new appType option allows us to define at a high level the different sets of middlewares (and options like sirv single: true in preview).

I think that 'custom' is less confusing than 'ssr' for the option that removes all the HTML middlewares and leaves the HTML handling to the framework.

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

[benmccann]

middlewareMode is a boolean now

[patak-dev]

This is for backward compat. We can break it directly for v3 thought

[bluwy]

I think they are only a handful of frameworks out there using middlewareMode: 'ssr' now that it should be safe to break. Otherwise another option is to log a warning, but framework authors would likely fix it right away so that end-users don't see it.

[brillout]

Should middlewareMode: true be the default when appType: 'ssr' is used?

We can't because SvelteKit is going to use appType: 'ssr' without middleware mode, as they are using the Vite server as is.

How about we make only vite.createServer() to default to middlewareMode: true when appType: 'ssr'?

While we keep middlewareMode: false for $ vite dev when appType: 'ssr'.

So that SvelteKit (and others) can still use $ vite dev instead of vite.createServer().

(Btw. I really like replacing ssr with custom. It addresses my concerns.)

CC @aleclarson.

[patak-dev]

Should middlewareMode: true be the default when appType: 'ssr' is used?

We can't because SvelteKit is going to use appType: 'ssr' without middleware mode, as they are using the Vite server as is.

How about we make only vite.createServer() to default to middlewareMode: true when appType: 'ssr'?

I actually like that middlewareMode only defines if the server is controlled by Vite or not, and that appType controls the type of app but has nothing to do with who manages the server. Given that this is an API that only advanced users will need I think it is better to keep middlewareMode and appType orthogonal.

[brillout]

Actually, how about a vite.createDevMiddleware()?

Before:

if (process.env.NODE_ENV === 'production') {
  app.use(sirv(`./dist/client/`))
} else {
  const vite = await import('vite')
  viteDevServer = await vite.createServer({
    server: { middlewareMode: true },
  })
  app.use(viteDevServer.middlewares)
}

After:

if (process.env.NODE_ENV === 'production') {
  app.use(sirv(`./dist/client/`))
} else {
  app.use((await import('vite')).createDevMiddleware())
}

It's low priority and I'm personally fine with the current API. But I can see many to welcome such aesthetic improvement and Vite 3 is a nice opportunity for that.

[benmccann]

How about we make only vite.createServer() to default to middlewareMode: true when appType: 'ssr'?
While we keep middlewareMode: false for $ vite dev when appType: 'ssr'.
So that SvelteKit (and others) can still use $ vite dev instead of vite.createServer().

That sounds confusing to me. I think it's better if it just always have the same value. I don't mind overriding the default value if needed. The question to me though is what is the better default and I think that generally false would be preferable

Actually, how about a vite.createDevMiddleware()?

It's not a compelling need, but it might be slightly nicer. I wouldn't be opposed to it as a follow-up

[benmccann]

lgtm. thank you so much for this!

[brillout]

better to keep middlewareMode and appType orthogonal.

That sounds confusing to me

👍 Ok that makes sense. You're right, it's clearer to separate both. Sorry for the noise.

As for createDevMiddleware(), I still think that it looks nicer than (await createServer({ server: { middlewareMode: true } })).middlewares. It's only aesthetics so I'm fine if we skip that part, although I do think that such aesthetics do contribute to Vite's zero-config feeling in a non-negligible way. Folks (rightfully) dread verbose configurations a la webpack.

Anyways, LGTM; green-check-marking this.

[patak-dev]

I agree with you @brillout, it feels strange to use a createServer function that doesnt creates a server. Maybe createServerMiddlewares to keep them aligned. We can do another PR to discuss with others

[brillout]

Maybe createServerMiddlewares to keep them aligned.

👍

Although I have a slight preference for createServerMiddleware() without s since it's expected that a middleware may be composed of multiple middlewares. (And it's actually technically speaking accurate: the returned value is a single middleware function (req, res, next) (that uses several middleware functions).)