Type MutateWithRequiredVariables does not satisfy the constraint MutateWithOptionalVariables

[geekox86]

Describe the bug

ERROR in /Users/geekox86/Documents/GitHub/OeMis/node_modules/@vue/apollo-composable/dist/useMutation.d.ts(45,340):
45:340 Type 'MutateWithRequiredVariables<TResult, TVariables>' does not satisfy the constraint 'MutateWithOptionalVariables<TResult, TVariables>'.
  Types of parameters 'variables' and 'variables' are incompatible.
    Type 'TVariables | undefined' is not assignable to type 'TVariables'.
      Type 'undefined' is not assignable to type 'TVariables'.
    43 |  * Use a mutation with variables, but without a default.
    44 |  */
  > 45 | export declare function useMutation<TResult = any, TVariables extends OperationVariables = OperationVariables>(document: DocumentNode | ReactiveFunction<DocumentNode>, options?: UseMutationOptionsNoVariables<TResult, undefined> | ReactiveFunction<UseMutationOptionsNoVariables<TResult, undefined>>): UseMutationReturn<TResult, TVariables, MutateWithRequiredVariables<TResult, TVariables>>;
       |                                                                                                                                                                                                                                                                                                                                                    ^
    46 | export {};
    47 | 
Version: typescript 3.8.3
Time: 2461ms

To Reproduce
Steps to reproduce the behavior:

1. Open node_modules/@vue/apollo-composable/dist/useMutation.d.ts
2. Go to L45 C340
3. See TypeScript error

Expected behavior
No errors.

Versions
vue: 2.6.11
@vue/composition-api: 0.5.0
@vue/apollo-composable: ^4.0.0-alpha.8
apollo-client: 2.6.8

Additional context
I used JetBrains Rider to look into the error.

[sylvaingi]

I'm able to reproduce if TS (currently 3.8.3) is configured with the strict option enabled.

[geekox86]

Yes, my TS is 3.8.3. Here is my package.json:

{
  "name": "oemis",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "serve": "vue-cli-service serve",
    "build": "vue-cli-service build"
  },
  "dependencies": {
    "@fortawesome/fontawesome-pro": "^5.13.0",
    "@vue/apollo-composable": "^4.0.0-alpha.8",
    "@vue/composition-api": "^0.5.0",
    "apollo-cache": "^1.3.4",
    "apollo-cache-inmemory": "^1.6.5",
    "apollo-client": "^2.6.8",
    "apollo-link": "^1.2.13",
    "apollo-link-batch-http": "^1.2.13",
    "apollo-link-scalars": "^0.1.6",
    "apollo-utilities": "^1.3.3",
    "core-js": "^3.6.4",
    "graphql": "^14.6.0",
    "graphql-anywhere": "^4.2.6",
    "graphql-tag": "^2.10.3",
    "moment": "^2.24.0",
    "roboto-fontface": "^0.10.0",
    "vue": "^2.6.11",
    "vue-router": "^3.1.6",
    "vuetify": "^2.2.21"
  },
  "devDependencies": {
    "@vue/cli-plugin-babel": "^4.3.1",
    "@vue/cli-plugin-router": "^4.3.1",
    "@vue/cli-plugin-typescript": "^4.3.1",
    "@vue/cli-service": "^4.3.1",
    "babel-plugin-graphql-tag": "^2.5.0",
    "sass": "^1.26.3",
    "sass-loader": "^8.0.2",
    "syncyarnlock": "^1.0.19",
    "typescript": "^3.8.3",
    "vue-cli-plugin-pug": "^1.0.7",
    "vue-cli-plugin-vuetify": "^2.0.5",
    "vue-template-compiler": "^2.6.11",
    "vuetify-loader": "^1.4.3"
  }
}

[tobias-kuendig]

I created a possible solution in #955.

Maybe someone can chime in and test the change. With the change incorporated, I got rid of all TS errors in my application. There might be other use-cases that are not covered, though.

[chanlito]

Facing this issue as well, anyone has a work around in the mean time?

[tobias-kuendig]

@chanlito Can you manually test this fix?

https://github.com/vuejs/vue-apollo/pull/955/files

You will have to patch this in
node_modules/@vue/apollo-composable/dist/useMutation.d.ts:45

[lucapircher]

@tobias-kuendig Applying your proposed change in #955 solves the issue for me.

[lucapircher]

@chanlito I do not face the issue if I use alpha.7

[bbugh]

Hi! 👋 I'm the original author for the types of v4 in #895 and I believe the issue you're reporting was caused by a9d9501.

There's an underlying incorrect assumption on my part that is causing this issue, that I believe will be resolved after the PR for #961. This is not correct, see comment below.

[bbugh]

Ok, I think issue #961 was the problem. Sorry for all of the comments, I must look like a crazy person now. 🤪 I blame 2+ months of quarantine.

I have submitted a PR here: #962 If you're invested in this outcome, please check it out.