serverless/lib/plugins/aws/utils/format-lambda-log-event.js

import dayjs from 'dayjs';
import utils from '@serverlessinc/sf-core/src/utils.js';

const { style } = utils;

export default (msgParam) => {
  let msg = msgParam;
  const dateFormat = 'YYYY-MM-DD HH:mm:ss.SSS';

  if (!msg.startsWith('REPORT')) msg = msg.trimRight();

  if (msg.startsWith('START') ||
    msg.startsWith('INIT_START') ||
    msg.startsWith('REPORT') ||
    msg.startsWith('END')) {
    msg = msg.replace('RequestId:', '-')
    msg = msg.replace('Version:', '- Version:')
    if (msg.includes('\tDuration:')) {
      msg = msg.split('\tDuration:').join('\nDuration:')
    }
    return style.aside(msg);
  }

  if (msg.trim() === 'Process exited before completing request') {
    return style.error(msg);
  }

  const splitted = msg.split('\t');

  if (splitted.length < 3) {
    return msg;
  }

  let date = '';
  let reqId = '';
  let level = '';

  if (!isNaN(new Date(splitted[0]).getTime())) {
    date = splitted[0];
    reqId = splitted[1];
  } else if (!isNaN(new Date(splitted[1]).getTime())) {
    date = splitted[1];
    reqId = splitted[2];
    level = `${splitted[0]}\t`;
  } else {
    return msg;
  }
  const text = msg.split(`${level || reqId}\t`)[1];
  const time = dayjs(date).format(dateFormat);

  return `${style.aside(`${time} - ${reqId} - ${level}`)}\n${text}`;
};