Add vitest 4.x support to @effect/vitest

[PaulRBerg]

Problem

The current @effect/vitest package (v0.27.0) declares a peer dependency on vitest: "^3.2.0", which causes warnings when used with vitest 4.x:

warn: incorrect peer dependency "vitest@4.0.14"

Vitest 4.0 was released and projects upgrading to it are now seeing peer dependency warnings when using @effect/vitest.

Solution

Update the peerDependencies in @effect/vitest to include vitest 4.x:

{
  "peerDependencies": {
    "effect": "^3.19.0",
    "vitest": "^3.2.0 || ^4.0.0"
  }
}

Note

This may require testing to ensure compatibility with vitest 4.x APIs. If there are breaking changes in vitest 4, additional code changes may be needed.

[PaulRBerg]

Related:

• @effect/vitest: Incompatibility with vitest 4.0 - onTestFinished API change #5976
• fix(@effect/vitest): fix compatibility with Vitest 4.0 (#5976) #5980

[ChristopherPHolder]

Is there any plans to upgrade?

[WikiRik]

@ChristopherPHolder I'm not a maintainer or anything, but I've read that Effect v3 is under a feature freeze with v4 betas being out (and published from https://github.com/Effect-TS/effect-smol ) which is updated to vitest 4.x. I wouldn't be surprised if that also means that Effect v3 remains on vitest 3.x

[PaulRBerg]

@WikiRik I don't see any problem in patching Effect v3 to make it officially compatible with vitest v4. The overwhelming majority of AI training data is on Effect v3, so this would prevent many issues down the line.