Resolvers for input object types on mutations?

[ngbrown]

I have a mutation that takes an input object.

  type Mutation {
    updateEntry(input: UpdateEntryInput!): CommandResult
  }

  input UpdateEntryInput {
    clientMutationId: String
    entryId: ID!
    newVersion: EntryChanges!
  }

  input EntryChanges {
    #...
  }

The Ids like entryId in the GraphQL system are Base64 obfuscated strings and I need to convert them back to integers to talk to the back-end services. EntryChanges is another input object with even more Ids that I need to convert back to integers.

I tried to add a resolver for UpdateEntryInput, Apollo Server crashed:

...\node_modules\graphql-tools\dist\schemaGenerator.js:297
                throw new SchemaError(typeName + " was defined in resolvers, but it's not an object");
                ^

Error: UpdateEntryInput was defined in resolvers, but it's not an object

What is wrong? I didn't find any good examples on how to handle this.

[negezor]

I join the question. This is very useful if you could transform the result from the input and perform the additionally validation of the data. In addition, it will be possible to simplify the validation code in the mutation itself.

[stubailo]

Yeah, unfortunately right now there is no way to process input types before they get passed to the resolver. That would probably be out of scope for being built into this library until it's added to the upstream graphql-js implementation this is based on.

It would take a lot of work, but I bet you could implement something like this using schema directives: https://dev-blog.apollodata.com/reusable-graphql-schema-directives-131fb3a177d1

[arizonatribe]

Yeah, too much work. But there were at least two suggestions on this thread which lean on custom directives instead.

[alexstrat]

For anyone interested, I implemented the idea of a resolver (called coercer) for input object in graphql-field-arguments-coercion. It can be used with graphql-tools to install the coercer functions and process the inputs before being passed to the field resolver.