feat: add config.operation

[brillout]

Description

This is solving a long standing problem: there isn't a reliable way to distinguish between dev and preview (since config.command === 'serve' for both $ vite dev and $ vite preview).

There are workarounds but none of them are reliable. (E.g. checking whether configureServer()/configurePreviewServer() is called doesn't work in certain situations.)

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[benmccann]

It's really a shame we can't call this command as it's quite confusing to have command be 'build'|'serve' and they feel a bit swapped. I wonder if we should name this new one cmd and deprecate the old command?

[brillout]

It's really a shame we can't call this command as it's quite confusing to have command be 'build'|'serve' and they feel a bit swapped.

Yes, I couldn't agree more.

I wonder if we should name this new one cmd

👍 Done.

and deprecate the old command?

I think so too. How about we already start showing a warning in the next patch release?

[sapphi-red]

I noticed that this change is a breaking change as it requires users to pass an additional argument to resolveConfig/loadConfigFromFile. We can avoid that by making the argument optional, but I fear that would lead to a same situation with configEnv.ssrBuild (#13809).

[bluwy]

We discussed about this in the meeting today. To minimize the changes, and since the main usecase is to only differentiate dev and preview, we think passing a isPreview property to ConfigEnv (the second param of the config hook) should be enough for now. resolveConfig can accept a new parameter to pass in the isPreview value.

This would make it work similar to the ssrBuild value today. ssrBuild is used to differentiate what kind of build is running, and isPreview would be used to differentiate what kind of server is running.

[brillout]

Neat, good idea. I'll try to update the PR later today.

[bluwy]

@brillout I've already opened a PR 😬 #14855

I forgot to credit you as a co-author for kicking this off though. Let me send a comment there so we do so before merging.

[brillout]

Neat. No need for credits.