fix: requires fixed version across the monorepo

[antfu]

Description

This PR makes vitest in peerDependencies as the fixed version. This enforces users to have a single version across the monorepo to have a stable and predictable behavior.

fix #4985 fix #4983

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[AriPerkkio]

Can users now end up with two different Vitest versions?

{
    "name": "my-project",
    "devDependencies": {
        "vitest": "~1.0.0",
        "@vitest/coverage-v8": "^1.2.0"
    }
}

In setup above the @vitest/coverage-v8 would install its own copy of vitest as their version ranges do not match. If vitest was declared as peerDependency, package managers should fail. Now they will happily install two versions, right?

[antfu]

There will always be different ways to have multiple versions - the users should take care of their package.json and lock file to ensure a single version (the same happens for any package). I'd consider the example package.json you provided a userland misconfiguration.

We could mention in the docs that we expect all packages to have a single version.

[sheremet-va]

I'd consider the example package.json you provided a userland misconfiguration.

It is a misconfiguration, but it might be hard to spot if the error is cryptic (like Cannot call .on on undefined) - we had these problems previously with the wrong peerDependency version and they will probably resurface here. If the package is in peerDependencies, the package manager will throw an error that the wrong version is installed.

[antfu]

Ok, makes sense. I saw Vue is doing this as well: https://github.com/vuejs/core/blob/07922dacc7422e828eb4238eac58dd11cd2cdb5c/packages/server-renderer/package.json#L48-L50

[antfu]

Updated

[AriPerkkio]

Looks good to me.

There's some code that I can now move from @vitest/coverage-* packages to vitest package to avoid duplication. Earlier as I though we needed backwards support inside same major, I simply had to duplicate the parts in coverage packages. Now they could simply share same code from vitest package. Refactoring PRs coming soon...