A gist with examples of how to create a higher-order component that receives a method with a generic spread variable parameter, and how to type constrain said spread

generic_spread.ts

/**
 * Example of a higher-order component with type-safety for functions with generic spread variables.
 * In this example, the HOC is a function to create AWS Lambda (for AWS API Gateway) function handlers.
 * All AWS Lambda exported handlers receive an (event, context) set of parameters.
 *
 * @author Adrian Gabardo <[email protected]>
 */

type LambdaResponse = Promise<any | void>;
type BaseLambda = (event, context) => LambdaResponse;

/**
 * A Lambda function that receives a generic/dynamic set of parameters (mixins).
 * @param event - AWS Lambda event object
 * @param context - AWS Lambda context object
 * @param mixins - A tuple of generic typing for dynamic spread variable types
 */
type MixedInLambda<T extends unknown[]> = (event, context, ...mixins: T) => LambdaResponse;

/**
 * An HOC that returns methods ready for usage with AWS Lambda.
 * @param handler - A custom function to be called by AWS Lambda.
 * @param mixins - Generic spread variables.
 * @returns - An AWS Lambda compatible function.
 */
const create_aws_lambda = <T extends unknown[]>(handler: MixedInLambda<T>, ...mixins: T): BaseLambda => async (event, context): LambdaResponse => {
    return await handler(event, context, ...mixins);
};

/**
 * EXAMPLE A 👇
 */

const squaredNumber = async (_event, _context, num: number) => {
  return num * num;
};

// This export is constrained to a second parameter of type number due to squaredNumber()'s parameter set.
export const squared_number_handler = create_aws_lambda(squaredNumber, 42);

/**
 * EXAMPLE B 👇
 */
const jsonStringifyWithLogging = async (_event, _context, id: string, logger: typeof console) => {
  const testObject = { test: true, id };
  logger.info("Stringifying:", testObject);
  return JSON.stringify(testObject);
};

// This export is constrained to a second parameter of string and a third of typeof console due to jsonStringifyWithLogging()'s parameter set.
export const json_stringify_handler = create_aws_lambda(
  jsonStringifyWithLogging,
  "1234-abcd",
  console
);