Custom resolvers for graphQL Mutation

Questions and Answers Strapi Backend
1
System Information
  • **Strapi Version 4.5.0:
  • **Operating System Ubuntu:
  • **Database sql:
  • **Node Version 16:
  • **NPM Version 6.14:
  • **Yarn Version unuse:

Hello,

I’am newbie to strapi. I was able to write lot of custom resolvers and to deport them outside of the index.ts file for purposes of code readability.
Now, want to create a custom mutation for create some complex and nested entity on Strapi. I’ll need to do that for complex creations needs. In order to begin, i’ve started to create a simple custom mutation.

Here the code i want to execute :

export default (strapi) => {
  const extensionService = strapi.plugin("graphql").service("extension");
  extensionService.use(({ strapi }) => ({
    typeDefs: `
          type Mutation {
            createEmptyContract(contractName: String!): [Contract]
          }
          `,
    resolvers: {
      Mutation: {
        createEmptyContract: {
          resolve: async (_, args) => {
            const contract = await strapi.entityService.create(
              "api:contract.contract",
              {
                data: {
                  label: args.contractName,
                },
              },
            );
            return contract;
          },
        },
      },
    },
  }));
};

I know that i can do that with native strapi endpoint, but in the futurei’ll need to do some more complex creation and i gonna need this kind of custom resolvers.
I get the following errors :

{
  "errors": [
    {
      "message": "Cannot read properties of undefined (reading 'attributes')",
      "locations": [
        {
          "line": 2,
          "column": 3
        }
      ],
      "path": [
        "createEmptyContract"
      ],
      "extensions": {
        "code": "INTERNAL_SERVER_ERROR",
        "exception": {
          "stacktrace": [
            "TypeError: Cannot read properties of undefined (reading 'attributes')",
            "    at createComponents (/app/node_modules/@strapi/strapi/lib/services/entity-service/components.js:21:11)",
            "    at Object.create (/app/node_modules/@strapi/strapi/lib/services/entity-service/index.js:135:33)",
            "    at processTicksAndRejections (node:internal/process/task_queues:96:5)",
            "    at async Object.<anonymous> (/app/node_modules/@strapi/strapi/lib/services/entity-service/index.js:310:20)"
          ]
        }
      }
    }
  ],
  "data": {
    "createEmptyContract": null
  }
}

Does any one have an idea ?