When an AJAX request raises an exception on the server, Rails will show a minimal error page with only basic information. Because all Unpoly Show archive.org snapshot updates work using AJAX requests, you won't get the more detailled better_errors Show archive.org snapshot page with the interactive REPL Show archive.org snapshot .
Below is an event listener that automatically repeats the request as a full-page load if your development error shows an error page. This means you get a second request, but the error page will show with full CSS and JavaScript.
The code assumes you are using Ruby on Rails with
better_errors
Show archive.org snapshot
, which is the default error view that modern Rails versions employ. If you are using another method to show development errors you need to update the isDevelopmentError() function so it returns true when your particular development server shows an error.
Warning
Unpoly cannot repeat form submissions that include file inputs. If it tries, the file data will be replaced with the string
[object File]instead, which likely results in a different error than the original. To avoid confusion, this code will instead redirect to/__better_errorswhen a file is included in the submission.
// Only do this in development. This requires a `[data-environment="development"]` attribute on your `<body>` element.
// See https://makandracards.com/makandra/1433-detect-the-current-rails-environment-from-javascript-or-css
if (document.body.dataset.environment === 'development') {
// Returns true when your development server shows an error page.
function isDevelopmentError(response) {
return !response.ok && /Full backtrace|Better errors/.test(response.text)
}
// When the development server shows an error page, repeat the request as a full page load.
up.on('up:fragment:loaded', function(event) {
if (isDevelopmentError(event.response)) {
event.preventDefault() // Prevent the fragment from being updated
if (event.request.params.toArray().some(({ name, value }) => value instanceof Blob)) {
up.network.loadPage({ url: '/__better_errors' }) // Unpoly can't resubmit requests with files
} else {
event.request.loadPage()
}
}
})
}
