AbstractDoctrineTypeDriver::normalizeFieldType() must be of the type string, null given

[dekamaru]

Q	A
Bug report?	yes
Feature request?	no
BC Break report?	no
RFC?	no

I want serialize Entity with Embeddables and get this error.

Error throwed by type-hint value mismatch $doctrineMetadata->getTypeOfField() returns DoctrineType|string|null, but JMS normalizeFieldType (AbastractDoctrineTypeDriver.php) have protected function normalizeFieldType(string $type): ?string signature and error happens.

It was happened after upgrade from symfony 3 to symfony 4, and all bundles updates.
In SerializerBundle 2.3 version all working good, because there is doc-block usage instead type-hint

I think you need set nullable type-hint in normalizeFieldType function.

Steps required to reproduce the problem

1. Serialize any Entity with Embedded property

Expected Result

• Serialized entity

Actual Result

• Argument 1 passed to JMS\Serializer\Metadata\Driver\AbstractDoctrineTypeDriver::normalizeFieldType() must be of the type string, null given

[goetas]

fixed by #1020