@middy/http-response-serializer/index.js

The Http Serializer middleware lets you define serialization mechanisms based on the current content negotiation.

"use strict";

const {
  normalizeHttpResponse
} = require('@middy/util');

const Accept = require('@hapi/accept');

const defaults = {
  serializers: [],
  default: undefined
};

const httpResponseSerializerMiddleware = (opts = {}) => {
  const options = { ...defaults,
    ...opts
  };

  const httpResponseSerializerMiddlewareAfter = async request => {
    var _request$event;

    if (request.response === undefined) return;
    request.response = normalizeHttpResponse(request.response); // skip serialization when content-type is already set

    if (request.response.headers['Content-Type'] || request.response.headers['content-type']) {
      return;
    } // find accept value(s)


    let types;

    if ((_request$event = request.event) !== null && _request$event !== void 0 && _request$event.requiredContentType) {
      types = [request.event.requiredContentType];
    } else {
      var _request$event$header, _request$event2, _request$event2$heade, _request$event3, _request$event3$heade, _ref;

      const acceptHeader = (_request$event$header = (_request$event2 = request.event) === null || _request$event2 === void 0 ? void 0 : (_request$event2$heade = _request$event2.headers) === null || _request$event2$heade === void 0 ? void 0 : _request$event2$heade.accept) !== null && _request$event$header !== void 0 ? _request$event$header : (_request$event3 = request.event) === null || _request$event3 === void 0 ? void 0 : (_request$event3$heade = _request$event3.headers) === null || _request$event3$heade === void 0 ? void 0 : _request$event3$heade.Accept;
      types = [...((_ref = acceptHeader && Accept.mediaTypes(acceptHeader)) !== null && _ref !== void 0 ? _ref : []), request.event.preferredContentType, options.default];
    }

    for (const type of types) {
      let breakTypes;

      for (const s of options.serializers) {
        if (!s.regex.test(type)) {
          continue;
        }

        request.response.headers['Content-Type'] = type;
        const result = s.serializer(request.response);

        if (typeof result === 'object' && 'body' in result) {
          request.response = result;
        } else {
          // otherwise only replace the body attribute
          request.response.body = result;
        }

        breakTypes = true;
        break;
      }

      if (breakTypes) break;
    }
  };

  const httpResponseSerializerMiddlewareOnError = httpResponseSerializerMiddlewareAfter;
  return {
    after: httpResponseSerializerMiddlewareAfter,
    onError: httpResponseSerializerMiddlewareOnError
  };
};

module.exports = httpResponseSerializerMiddleware;