I'm getting an "Argument has invalid value" error message when using FilterInputObjectFields

[wujekbogdan]

Here's a sample schema I'm playing with:

import { createYoga } from 'graphql-yoga';
import { stitchSchemas } from '@graphql-tools/stitch';
import { Transform } from '@graphql-tools/delegate/typings/types';
import { makeExecutableSchema } from '@graphql-tools/schema';

export type Transforms = Array<Transform<any, Record<any, any>>>;

const mySchema = makeExecutableSchema({
  typeDefs: /* GraphQL */ `
    input ReviewInput {
      stars: Int!
      commentary: String
    }

    type Mutation {
      createReview(review: ReviewInput!): String
    }
  `,
  resolvers: {
    Mutation: {
      createReview: () => 'Success!',
    },
  },
});

export const useGateway = async (transforms: Transforms) => {
  const stitchedSchemas = stitchSchemas({
    subschemas: [
      {
        schema: mySchema,
        transforms,
      },
    ],
  });

  return createYoga({
    landingPage: false,
    schema: stitchedSchemas,
  });
};

Here's the transformation that removes the stars input argument:

const gateway = await useGateway([
  new FilterInputObjectFields((typeName, fieldName) => {
    return !(typeName === 'ReviewInput' && fieldName === 'stars');
  }),
]);

The filter works as expected, I see the stars field being removed from the ReviewInput argument:

But when I submit the mutation I'm getting the following error:

{
  "errors": [
    {
      "message": "Argument \"review\" has invalid value {commentary: \"test\"}.",
      "locations": [
        {
          "line": 2,
          "column": 24
        }
      ],
      "path": [
        "createReview"
      ]
    }
  ],
  "data": {
    "createReview": null
  }
}

Am I missing something? Is there something else left to do after applying the FilterInputObjectFields transformation?

---

EDIT:

If I filter-out the commentary field:

const gateway = await useGateway([
  new FilterInputObjectFields((typeName, fieldName) => {
    return !(typeName === 'ReviewInput' && fieldName === 'commentary');
  }),
]);

Then everything works as expected. I'm getting the success message:

{
  "data": {
    "createReview": "Success!"
  }
}

The only difference between these two fields is that one is an optional field and the other is a required field. This makes me wonder if filtering out required fields needs some special treatment. I was expecting FilterInputObjectFields to take care of everything.

---

EDIT:

I've just realised that everything works as expected. If I wrap/stich a schema than the original schema remains unchanged. Reqests are delegated to the original schema where required fields still remain required :)