Note: add a section about functional tests that mentions the before/after behavior around testing exceptions.

@yceruto I'm working on this and I'm having lots of problems trying to understand the changes needed in this page: https://symfony.com/doc/current/controller/error_pages.html

Before, things worked like this:

1. Customize the visible error pages of your site: use Twig template overriding.
2. View in dev how errors look in prod: use /_error/{code}.{format}
3. Run custom logic on exceptions: listen to kernel.exception event.
4. Do advanced stuff with the dev exceptions: use twig.exception_controller to override the default controller.

Now, how do we do those things?

1. I don't know. The "templates" are hardcoded in the error renderers.
2. It looks like the URL changed to /{code}.{format}. If this is right, isn't it confusing to not add some prefix like /_error/ in the URL?
3. Same as before. No changes in this feature.
4. I don't know. Not possible anymore? The framework.error_controller value is not really used in the default ErrorController, right? (It's only used in the preview() action)

Thanks!

1. Customize the visible error pages of your site: use Twig template overriding.

1. I don't know. The "templates" are hardcoded in the error renderers.

If TwigBundle is enabled, same as before, you can create the error pages in:

• templates/bundles/TwigBundle/Exception/error.html.twig
• or templates/bundles/TwigBundle/Exception/error404.html.twig

The difference is that now you can't create non-HTML error pages like error.json.twig, so you must define your own JsonErrorRenderer instead.

2. View in dev how errors look in prod: use /_error/{code}.{format}

2. It looks like the URL changed to /{code}.{format}. If this is right, isn't it confusing to not add some prefix like /_error/ in the URL?

As before, the path prefix is defined when we import the routing config, see recipe changes symfony/recipes#645

3. Run custom logic on exceptions: listen to kernel.exception event.

3. Same as before. No changes in this feature.

No changes.

4. Do advanced stuff with the dev exceptions: use twig.exception_controller to override the default controller.

4. I don't know. Not possible anymore? The framework.error_controller value is not really used in the default ErrorController, right? (It's only used in the preview() action)

Yes, it's possible as before, the framework.error_controller config can be used if TwigBundle is not installed or if twig.exception_controller is set to null explicitly. The new one (framework.error_controller) has the same mean. By default the ErrorController is used for both actions: Rendering the error response and Preview the error response in non-debug mode.

2. View in dev how errors look in prod: use /_error/{code}.{format}

2. It looks like the URL changed to /{code}.{format}. If this is right, isn't it confusing to not add some prefix like /_error/ in the URL?

As of now, the prefix has double undercore: __error/. That was needed to avoid conflic with the same config in routes/dev/twig.yaml this has been updated and now it works as before.

I ran into this while upgrading to symfony 5.0. Since the docs haven't been updated yet, it left me very confused until I found this issue. I shall try to open a PR this sunday to hopefully help others who run into the same issue :)

Hello @dbrekelmans, my previous comment is outdated.

I'm sorry, I don't have time to write/fix the documentation, but I can review any PR about it.

Note: There is no such a component ErrorRenderer nor the JsonErrorRenderer service. Now all these features are handled by the new ErrorHandler component. The customization of the Twig-based HTML error pages work as before by installing the TwigBundle and the serializer component (if installed/enabled) will be used for non-HTML error responses.

Hi @yceruto,

This was more work than I expected, but I managed to do most of it.
The only thing I'm struggling with is the Overriding the Default ErrorController paragraph in controller/error_pages.rst.

Would you mind if I open a PR with the changes I have so far?
Maybe someone else can jump in and finish the last section.

You can preview my changes here: https://github.com/dbrekelmans/symfony-docs/compare/4.4...dbrekelmans:fix_12273

Yes, please, submit the changes to this repo, so we can review it, thanks!