Express error handler for user-friendly postgres errors

errorHandler.js

import { errorHandler } from 'express-rest-error'; // need version 1.2.0+

// Make postgres errors more user-friendly
const pgErrorPatterns = [
  {
    regex: /null value in column "(.*)" violates not-null constraint/,
    assign: (match) => ({
      message: `${match[1]} is required`,
      required: [match[1]],
    }),
  },
];

// error handler is last
app.use(
  errorHandler({
    debug: true,
    transform: ({ err, req, res, responseBody }) => {
      pgErrorPatterns.some((pattern) => {
        const match = err.message.match(pattern.regex);
        if (match) {
          Object.assign(responseBody, pattern.assign(match));
          err.httpStatus = 400;
          //res.status(400);
        }
        return !!match;
      });
      return responseBody;
    },
  })
);