How to implement custom directive on ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION

[UchihaYuki]

I want to implement the following directive

export const validateDirectiveTypeDefs = `
  input RegExp {
    pattern: String!
    flags: String
  }

  directive @validate(
    gt: Int
    gte: Int
    lt: Int
    lte: Int
    noBlank: Boolean
    minLength: Int
    maxLength: Int
    regExp: RegExp
    minItems: Int
    maxItems: Int
  ) on ARGUMENT_DEFINITION | INPUT_FIELD_DEFINITION
`;

But I found the resolve function doesn't get called

export function validateDirectiveTransformer(schema: GraphQLSchema) {
  return mapSchema(schema, {
    [MapperKind.ARGUMENT]: (
      argumentConfig: GraphQLArgumentConfig,
      fieldName: string,
      typeName: string,
      schema: GraphQLSchema
    ) => {
      const validateOptions = getDirective(
        schema,
        argumentConfig,
        "validate"
      )?.[0] as ValidateOptions;
      if (!validateOptions) return argumentConfig;

      if (validateOptions.regExp) {
        const { pattern, flags } = validateOptions.regExp as any as {
          pattern: string;
          flags: string;
        };
        validateOptions.regExp = new RegExp(pattern, flags);
      }
      const config = schema
        .getType(typeName)
        .toConfig() as GraphQLObjectTypeConfig<any, any>;
      const fieldConfig: GraphQLFieldConfig<any, any, any> =
        // @ts-ignore
        config.fields[fieldName];
      const { resolve = defaultFieldResolver } = fieldConfig;
      fieldConfig.resolve = async function (source, args, context, info) {
        // This function doesn't get called at all
        const value = args[argumentConfig.astNode.name.value];
        args[argumentConfig.astNode.name.value] = validate(value, validateOptions);
        return await resolve(source, args, context, info);
      };
      return argumentConfig;
    },
  });
}

my operation

extend type Mutation {
  enter(
    age: Int! @validate(gte: 18)
  ): Boolean!
}

Some code above is just my guessing, the doc is not complete.

[UchihaYuki]

[MapperKind.OBJECT_FIELD]: (fieldConfig) => {
      const newFieldConfig = { ...fieldConfig };
      let { resolve = defaultFieldResolver } = fieldConfig;

      for (const argName in fieldConfig.args) {
        const argConfig = fieldConfig.args[argName];
        const validateOptions = getDirective(
          schema,
          argConfig,
          "validate"
        )?.[0] as ValidateOptions;
        if (!validateOptions) continue;

        if (validateOptions.regExp) {
          const { pattern, flags } = validateOptions.regExp as any as {
            pattern: string;
            flags: string;
          };
          validateOptions.regExp = new RegExp(pattern, flags);
        }

        const oldResolve = resolve;
        resolve = async function (source, args, context, info) {
          const value = args[argName];
          args[argName] = validate(value, validateOptions);
          return await oldResolve(source, args, context, info);
        };
      }

      newFieldConfig.resolve = resolve;
      return newFieldConfig;
    },

I solved it. For your reference.