[vue-query]: UseMutationReturnType default names unexported MutationResult (TS2883) 🤖🤖🤖

[earthabledev]

Describe the bug

@tanstack/vue-query 5.104.0 publishes UseMutationReturnType with a default type argument that names MutationResult. MutationResult is not exported. A project that emits declarations (composite: true, which implies declaration) cannot name the inferred return type of an exported wrapper around useMutation.

TypeScript reports:

TS2883: The inferred type of 'useExampleMutation' cannot be named without a reference to 'MutationResult' from '@tanstack/vue-query/build/modern/useMutation'. This is likely not portable. A type annotation is necessary.

@ts-expect-error on the export suppresses TS2883 and is then reported as unused (TS2578). The diagnostic is produced during declaration emit, after TypeScript decides whether the directive was used. @ts-ignore is not a substitute we can use.

5.91.2 still declares the private alias, but the published .d.ts re-exports the function with export { type UseMutationReturnType, useMutation }. That form typechecks. 5.104.0 uses export type UseMutationReturnType<..., TResult = MutationResult<...>> and export declare function useMutation, and declaration emit then has to name MutationResult.

Related, and not the same report:

• [vue-query]: Fresh Vue3 project + Tanstack - Typescript errors, This is likely not a portable. #6318 (closed) was an earlier "not portable" failure from tsup renaming exports.
• TS2883: Type declarations break with TypeScript nodenext module resolution #11038 (closed) was TS2883 under nodenext from experimentalDts.
• vue-query: queryOptions()'s real return type is unexported; the public name with the same identifier points at a different, legacy type #11042 (open) is the same class of bug for queryOptions(), not for useMutation.

Your minimal, reproducible example

No hosted sandbox. vue-tsc --build against a composite project is the reproduction. The three files below are complete.

package.json

{
  "private": true,
  "type": "module",
  "dependencies": {
    "@tanstack/vue-query": "5.104.0",
    "vue": "3.5.43"
  },
  "devDependencies": {
    "typescript": "6.0.3",
    "vue-tsc": "3.3.11"
  }
}

tsconfig.json

{
  "compilerOptions": {
    "composite": true,
    "module": "esnext",
    "moduleResolution": "bundler",
    "strict": true,
    "target": "esnext",
    "skipLibCheck": true
  },
  "include": ["src"]
}

src/useExampleMutation.ts

import { useMutation } from '@tanstack/vue-query'

export const useExampleMutation = () => {
  return useMutation({
    mutationFn: async () => 'ok',
  })
}

Steps to reproduce

1. Install the three files above.
2. Run pnpm exec vue-tsc --build --noEmit --force.
3. See TS2883 on useExampleMutation.
4. Repeat with @tanstack/vue-query 5.91.2. The same command exits 0.

Expected behavior

An exported wrapper around useMutation should typecheck under composite / declaration emit without naming a private type. MutationResult should be exported, or it should not appear as a default type argument on the public UseMutationReturnType.

How often does this bug happen?

Every time

Platform

• OS: macOS
• Browser: not applicable (vue-tsc)
• Version: TypeScript 6.0.3, vue-tsc 3.3.11, Vue 3.5.43

Tanstack Query adapter

vue-query

TanStack Query version

5.104.0 (does not reproduce on 5.91.2)

TypeScript version

6.0.3

Additional context

Annotating the wrapper as UseMutationReturnType<TData, TError, TVariables, unknown> is not assignable to the value useMutation returns, because that value is instantiated with the private fifth type argument. The annotation only typechecks if the consumer copies MutationResult (DistributiveOmit<MutationObserverResult<...>, 'mutate' | 'reset'>). That copy has to stay in sync with an unexported alias.