uk-gov-mirror / dfe-digital.login.dfe.express-error-handling

Error handling middleware for express applications

login.dfe.express-error-handling

Error handling middleware for express applications

Usage

Error Handler middleware

The error handler middleware provides a standard express error handler middleware function that will log the error and return a 500 result. It takes an object that can have a logger and errorPageRenderer.

logger should be an object that has an error function on it, with a signature error(message, details); where message is a string nad details is an object.

errorPageRenderer is optional, but if passed, should be a function that can take an error and return an object with properties content and contentType. These will be used as the respective details in the response.

const { getErrorHandler } = require('login.dfe.express-error-handling');
const errorPageRenderer = (error) => {
  render('500', {error});
}

app.use(getErrorHandler(logger, errorPageRenderer))

asyncWrapper

The asyncWrapper can be used to wrap async actions for express, so that errors are handled and passed through the standard express error chain.

const { asyncWrapper } = require('login.dfe.express-error-handling');

app.use('/my-route', asyncWrapper(async (req, res) => {
  await someAction();
  
  res.status(204).send();
}));

EJS Error Page Renderer

The package includes an EJS error page renderer:

const { getErrorHandler, ejsErrorPages } = require('login.dfe.express-error-handling');

const showErrorDetailsOnPage = false; // You can include error details on the page in appropriate environments

// Links to common locations, such as help or static assets
const urls = { 
  help: 'http://url.to/help'
  assets: 'http://cdn.with.assets',
  assetsVersion: 'v1'
}; 
//assetsVersion is a string that will be added when requesting static assets
// http://cdn.with.assets/assetName?version=v1

const errorPageRenderer = ejsErrorPages.getErrorPageRenderer(urls, showErrorDetailsOnPage);

app.use(getErrorHandler({
  logger,
  errorPageRenderer,
}));