Validate deprecated mutation inputs?

[fiznool]

Firstly, thank you for this awesome project. I'm using it very successfully to detect usage of @deprecated fields, queries and mutations in any incoming requests, so I can better understand which clients are sending older requests to my server.

As I'm using Apollo Server, I have created an Apollo plugin to perform this:

import { validate } from '@graphql-inspector/core';
import { print, Source } from 'graphql';

const logDeprecatedFieldsPlugin: ApolloServerPlugin = {
  async requestDidStart() {
    return {
      async didResolveOperation({ context, operation: operationAST }) {
        const { logger } = context;

        const operation = print(operationAST);
        const results = validate(schema, [new Source(operation)]);

        const deprecatedResults = results
          .filter((r) => r.deprecated.length > 0)
          .flatMap((r) => r.deprecated);

        if (deprecatedResults.length > 0) {
          logger.debug(
            { operation, deprecatedResults },
            'Deprecated GraphQL usage detected'
          );
          deprecatedResults.forEach((r) => {
            logger.debug(`GraphQL deprecation: ${r.message}`);
          });
        }
      },
    };
  },
};

As mentioned, this works perfectly for any deprecated query, mutation or field. However, I cannot figure out how to detect any deprecated mutation inputs.

By way of example, take the following schema:

mutation {
  createCustomer(input: CreateCustomerInput!): CreateCustomerPayload!
}

type CreateCustomerInput {
  name: String @deprecated(reason: "Use givenName and familyName instead")
  givenName: String
  familyName: String
}

type CreateCustomerPayload {
  createdCount: Int!
}

If I send the following query, the deprecated name field is not detected:

mutation createCustomer {
  createCustomer(input: { name: "Homer Simpson" } ) {
    createdCount
  }
}

If variables are used instead, my code also doesn't detect this:

mutation createCustomer($input: CreateCustomerInput!) {
  createCustomer(input: $input ) {
    createdCount
  }
}

{
  "input": {
    "name": "Homer Simpson"
  }
}

For this second case, as the operation AST does not directly include the query variables, I can understand why this would not be detected. In the Apollo plugin, didResolveOperation includes a request.variables object, which contains the variable values, but I can't figure out how to use this with the operation to pass to validate.

If anyone can help or offer guidance, it would be much appreciated!