Symfony version(s) affected

5.3

Description

The denormalization of array with null value in previous index to Symfony\Component\ErrorHandler\Exception\FlattenException is failing.

The denormalize method check if previous index is set and not if it is not null. Moreover, the setPrevious method of FlattenException strictly expect a FlattenException instance.

[Symfony\Component\Messenger\Exception\MessageDecodingFailedException]
  Could not decode stamp: Failed to denormalize attribute "previous" value fo
  r class "Symfony\Component\ErrorHandler\Exception\FlattenException": Expect
  ed argument of type "Symfony\Component\ErrorHandler\Exception\FlattenExcept
  ion", "null" given at property path "previous".

How to reproduce

Hard to say for all cases, but in my case it happens when messenger:consume command fails due to a Symfony\Component\Messenger\Exception\HandlerFailedException.

Possible Solution

Fix the type of the argument of the setter:

<?php

class FlattenException
{

    /**
     * @return $this
     */
    public function setPrevious(?self $previous): self
    {
        $this->previous = $previous;

        return $this;
    }

Additional Context

No response