Mapping Transformer + Sf5 + old key syntax is failing

[shavounet]

Description

To be analysed : I found an issue with the old mapping syntax and Sf5

• failing line : https://github.com/cleverage/process-bundle/blob/v3.2-dev/Transformer/MappingTransformer.php#L141
• error Transformation 'mapping' have failed: Symfony\Component\PropertyAccess\PropertyAccessor::isPropertyWritable(): Argument #1 ($object) must be of type object, array given

mapping:
  mapping:
    key1: ....            # <= this doesn't work anymore if input is an array 
    '[key2]': ....        # <= this is ok 

Maybe it's time to depreciate it ?

Requirements

• Documentation updates
  • Reference
  • Cookbooks
  • Changelog
• Unit tests

Breaking changes