Allow disabling spa middleware

[Artur-]

Clear and concise description of the problem

We are running Vite from Java and to talk to the dev server, we use its http server. We are kind of wanting to run it in middleware mode but cannot use middleware mode directly. In this case, the viteSpaFallbackMiddleware is undesireable as the actual SPA part of the application is handled through a Java server and we want to load frontend resources from Vite. Having the spa middleware enable makes it impossible to know if a certain URL refers to a frontend resource or not, as all URLs that do not refer to resources will still return 200 and the index.html contents.

Suggested solution

Add an option to disable viteSpaFallbackMiddleware even when the middleware option is off.

Alternative

We are currently removing the middleware by force using something like

              context.server.middlewares.stack = context.server.middlewares.stack.filter((mw) => {
                const handleName = '' + mw.handle;
                return !handleName.includes('viteSpaFallbackMiddleware');
              });

It is not pretty

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.

[Artur-]

I'd be happy to create a PR for this but I will wait for some input first, like how the configuration should be done

[Niputi]

reference about disabling middlewares #4640

[Artur-]

I can only think of one solution which makes sense and that would be a ServerOption like

    /**
     * When `true`, the index page is sent as the response to all requests 
     * which do not refer to a resource.
     */
    spa?: boolean

Or if it is desirable that the default value is false, disableSpa

All other solutions I can think of imply

• the middleware names become public API
• the user must understand what each middleware does
• the API is based on internal details and not on functionality

All which sound quite undesirable

[brillout]

See #8061.

[benmccann]

Implemented in #8217