Fixed type definition for subscribe

[intellix]

Checklist:

• If this PR is a new feature, please reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• Try to include the Pull Request inside of CHANGELOG.md

According to apollo-client it returns a FetchResult whereas apollo-angular says it's an any: https://github.com/apollographql/apollo-client/blob/7eaf4132cd2cd6244260777799406aaa03fcf377/packages/apollo-client/src/ApolloClient.ts#L355

[intellix]

@kamilkisiela any idea why the above 2 checks aren't finishing after days?

[kamilkisiela]

@intellix could you rebase?

[intellix]

Rebased @kamilkisiela

[kamilkisiela]

Thank you @intellix !! 🚀 🥇

[kamilkisiela]

v1.7.0

[PowerKiKi]

I think this is a breaking change that should have been release as a major version. It would typically break the following code:

export interface Login {
  login: boolean;
}

this.apollo.mutate<Login>({
    mutation: loginMutation,
    variables: loginData,
}).pipe(map(({data: {login}}) => login));

With an error similar to:

error TS2339: Property 'login' does not exist on type 'Login | null | undefined'.

This is because ultimately ExecutionResult is defined with a nullable data property in graphql package. So all existing mutations must be adapted accordingly.

I am not sure why data is nullable though, I believe in the context of apollo-angular (not graphql), a mutation either succeeds and its data is exactly as defined in the mutation itself (probably often non-nullable), or the mutation fails and it goes through the observable error mechanism. But we should never force a mutation result to be nullable... or should we ?

[PowerKiKi]

@intellix @kamilkisiela do you have any thoughts on my comment ?

As is it is pretty much impossible to use strictNullChecks in combinaison with this PR.

[PowerKiKi]

I digged deeper in this issue and finally figured out the issue is in apollo-client. For details see apollographql/apollo-client#5662