How to return both errors and data with Apollo server? - apollo-server

Question

I know Apollo can return a combination of errors and data, the client documentation even covers this: and I believe this can happen automatically when field resolvers run into issues, but how can I manually return mixed payloads? I have use cases in my project where users will send large amounts of data to mutate in the form of an input array. Some members of the array might be malformed and I want to throw validation errors for those but I still want the other changes to go through. An example pseudo request and response pair would be:
// input
{
mutateEntities: [
entityAMutationInput,
entityBMutationInput,
entityCMutationInput,
entityDMutationInput,
]
}
// response
{
data: {
mutateEntities: [
entityAMutationPayload,
entityBMutationPayload,
]
},
// members of the error array seem to refer to individual GQL operations in Apollo so
// there would only be one here
errors: [{
...errorMetadata
extensions: {
validationErrors: [
entityCValidationError,
entityDValidationError
]
}
}]
}
I realise that I have the option of defining errors as a GQL type and including them as part of the payload data but our FE team already has error handling that expects errors to appear in payload.errors and not, for example, payload.data.validationErrors or some other custom field. I want my errors to appear in payload.errors.extensions.validationErrors to minimise the impact on the front end. I know how to do this if I throw a custom error but, if I throw errors, then I won't have any data under payload.data.mutateEntities.