How to add decorator to args param in graphql?

@larissa 

You can add a decorator to the args parameter in GraphQL by creating a custom directive in your schema and using it to decorate the args in your resolver functions. Here is an example of how you can add a decorator to the args parameter:

1. Define a custom directive in your schema:

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directive @validateInput(rule: String!) on ARGUMENT_DEFINITION

1. Add the directive to the args parameter in your resolver function:

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const resolvers = {
  Query: {
    myQuery: async (_, { input }, context) => {
      // Your resolver logic here
    },
  },
};

resolvers.Query.myQuery.validation = {
  input: [
    async (next, src, { rule }, args) => {
      // Check if the input args meet the validation rules
      if (!args.input) {
        throw new Error("Input is required");
      }
      // Invoke the next function if the validation passes
      return next(args);
    },
  ],
};

module.exports = resolvers;

In this example, we added a custom directive called validateInput with a parameter rule that specifies the validation rule to be applied to the args parameter in the resolver function. The validation logic is implemented in a decorator function that is added to the validation property of the resolver function.

When the resolver function is called, the decorator function will be triggered to validate the args parameter based on the specified rule before executing the resolver logic.

By using custom directives and decorator functions, you can easily add validation or any other custom logic to the args parameter in your GraphQL resolver functions.