fix(server): do not create server if there is no entry

[btea]

Description

Now even if the entry is not determined, the server will create , and when it is opened directly in the browser, it will appear as shown in the figure below.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[sun0day]

I think it would be better to show a warning instead of throwing an error

[bluwy]

Similar to #12096, it'll need a lot more checks and a warning instead of an error to get this right. But it also introduces a glob on every dev startup, and I'm not sure if it's worth the cost.

[btea]

In fact, a warning message is currently output when scanImports. However, the server has been created at this time, but as mentioned above, it cannot be accessed, so I want to throw an error message directly before the creation to terminate the server creation.

However, as @bluwy said, this seems to be cumbersome and requires a lot of checking. Currently, I can't pinpoint exactly when an error is thrown such that the test fails.

[bluwy]

The test fail is coming from ssr-pug because it doesn't have any HTML files. The solution would be configuring the optimizeDeps.entries to JS files instead since Vite doesn't know how to scan pug files. Though even if this is fixed, there's still the perf penalty mentioned before.

For the current import scan warning, it only happens when there's no Vite cache existing, so it'll only happen in cold starts (partly also for performance).

[bluwy]

I'll close this for now as there are perf concerns, plus it might likely not working with SSR setups like Vitest that spins up the server and doesn't expect an entrypoint to necessarily exist. Thanks for looking into this!