Make "hydra:mapping" item's property nullable

[GaryPEGEOT]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no

Context

My entites have the following filter, to select properties. Parameter name have been overrode.
* @ApiFilter(PropertyFilter::class, arguments={"parameterName": "fields"})

And I got the following error in my tests, using assertMatchesResourceCollectionJsonSchema assertion

   │             ...
   │             3 => Array &9 (
   │                 '@type' => 'IriTemplateMapping'
   │                 'variable' => 'fields[]'
   │                 'property' => null
   │                 'required' => false
   │             )
   │             ...
   │     )
   │ ) matches the provided JSON Schema.
   │ hydra:search.hydra:mapping[3].property: NULL value found, but a string is required

[GaryPEGEOT]

Turns out justinrainbow/json-schema doesn't seems to support nullable properties: jsonrainbow/json-schema#551

[alanpoulain]

'nullable' => true is only for OpenAPI < 3.1.
I don't think we should add it here.

[GaryPEGEOT]

Ok. the change from string to 'type' => ['string', 'null'], broke Behat pipelien, I'll update the tests as well if you're OK with the change ?

[alanpoulain]

Yes I think this change is necessary.

[GaryPEGEOT]

It seems that 'null' is valid type starting on Open-API 3.1 and the schema generated by the api:openapi:export command is at "3.0.2", so it wont pass swagger-cli validation (which is normal). I could check the version to add nullable or ['string', 'null'] combo, but I don't think you have control over the generated minor version. Any idea on how to solve this ?

[alanpoulain]

It's more or less what it has been done here:

core/src/JsonSchema/TypeFactory.php

Lines 155 to 184 in f53bb64

	private function addNullabilityToTypeDefinition(array $jsonSchema, Type $type, ?Schema $schema): array
	{
	if ($schema && Schema::VERSION_SWAGGER === $schema->getVersion()) {
	return $jsonSchema;
	}
	if (!$type->isNullable()) {
	return $jsonSchema;
	}
	if (\array_key_exists('$ref', $jsonSchema)) {
	return [
	'nullable' => true,
	'anyOf' => [$jsonSchema],
	];
	}
	if ($schema && Schema::VERSION_JSON_SCHEMA === $schema->getVersion()) {
	return array_merge(
	$jsonSchema,
	[
	'type' => \is_array($jsonSchema['type'])
	? array_merge($jsonSchema['type'], ['null'])
	: [$jsonSchema['type'], 'null'],
	]
	);
	}
	return array_merge($jsonSchema, ['nullable' => true]);
	}

[GaryPEGEOT]

Fixed ! I've kept nullable for openapi version, but if it's not necessary I'll move it to a ternary.

[alanpoulain]

Could you initialize the property before the switch and rename it $nullableStringDefinition? In case we want to reuse it elsewhere.

[GaryPEGEOT]

Fixed!

[alanpoulain]

Thank you @GaryPEGEOT.