ThomasAribart

import middy from '@middy/core';

// Business logic
const businessLogic = async (event) => {
  ...
  return myResponse;
};

// Configuration
export const myHandler = middy(businessLogic).onError(handleError);

ThomasAribart

const handler = async () => ({
  statusCode: 200,
  body: JSON.stringify({ fruits: ['What a great tomato'] }),
  headers: { 'Content-Type': 'application/json' },
});

ThomasAribart

const formatErrorForApiGateway = ({ error }) => {
  const { statusCode, key, message } =
    error instanceof CustomError
      ? error
      : new InternalServerError({ message: error.message });
  throw `[${statusCode}] [${key}] ${message}`;
};

ThomasAribart

const parseStatusCode = (originalStatusCode) => {
  switch (true) {
    case defaultStatusCodes.has(originalStatusCode):
      return originalStatusCode;
    case originalStatusCode < 500:
      return 400;
    default:
      return 500;
  }
};

ThomasAribart

const defaultStatusCodes = new Set([400, 401, 403, 404, 422, 500, 502, 504]);

class CustomError extends Error {
  constructor(statusCode: number, { key, message, payload }) {
    super(message);
    if (!defaultStatusCodes.has(statusCode)) {
      throw new Error(`No integration response associated with statusCode ${statusCode}`);
    }
    ...
  }

ThomasAribart

const parseError = (originalError, parsers) => {
  let error = originalError;

  while (!(error instanceof CustomError) && parsers.length) {
    const { detect, parse } = parsers[0];
    if (detect(error)) {
      error = parse(error);
    }
    parsers.shift();
  }

ThomasAribart

const formatErrorForApiGateway = ({ parsers } = { parsers: [] }) =>
  ({ error }) => {
    const { statusCode, key, message } = parseError(error, parsers);
    throw `[${statusCode}] [${key}] ${message}`;
  };

...

const handler = middy(businessLogic)
  .onError(formatErrorForApiGateway({ parsers: [parseAxiosError] });

ThomasAribart

functions:
  myLambda:
    ...
    integration: lambda
    response:
      statusCodes:
        200:
          pattern: '' # Default response method
        400:
          pattern: '.*"statusCode":400.*'

ThomasAribart

const formatErrorForApiGateway = ({ parsers } = { parsers: [] }) =>
  ({ error }) => {
    const { statusCode, key, message } = parseError(error, parsers);
    throw JSON.stringify({ statusCode, key, message });
  };

ThomasAribart

functions:
  myLambda:
    ...
    integration: lambda
    response: ${file(./response.yml)}