XML mapping doesn't take account of the attribute `nullable` for embedded document

[wuchen90]

Bug Report

Q	A
BC Break	no
Version	2.2.0

Summary

I use XML to map the documents.
When I set the attribute nullable=true to a property, which is an embedded document (embed-*), the ClassMetadata resulted always set this property to ClassMetadata->isNullable() === false.
By the way, mapping with annotations works well.

Here is an example of the mapping:

<document name="Model\Cart" collection="carts">
        <embed-one field="shippingAddress" target-document="Model\ShippingAddress" nullable="true"/>

Current behavior

Whatever the attribute nullable is, when it's set to an embedded document property, the ClassMetadata->isNullable() always returns false.
For annotation mapping, there is no problem because all the metadata provided in annotations are merged to build the ClassMetadata.
But for XML, the metadata are built attribute by attribute and there is no part dealing with nullable.
See

mongodb-odm/lib/Doctrine/ODM/MongoDB/Mapping/Driver/XmlDriver.php

Lines 354 to 395 in 8069ded

	private function addEmbedMapping(ClassMetadata $class, SimpleXMLElement $embed, string $type): void
	{
	$attributes = $embed->attributes();
	$defaultStrategy = $type === 'one' ? ClassMetadata::STORAGE_STRATEGY_SET : CollectionHelper::DEFAULT_STRATEGY;
	$mapping = [
	'type' => $type,
	'embedded' => true,
	'targetDocument' => isset($attributes['target-document']) ? (string) $attributes['target-document'] : null,
	'collectionClass' => isset($attributes['collection-class']) ? (string) $attributes['collection-class'] : null,
	'name' => (string) $attributes['field'],
	'strategy' => (string) ($attributes['strategy'] ?? $defaultStrategy),
	];
	if (isset($attributes['field-name'])) {
	$mapping['fieldName'] = (string) $attributes['field-name'];
	}
	if (isset($embed->{'discriminator-field'})) {
	$attr = $embed->{'discriminator-field'};
	$mapping['discriminatorField'] = (string) $attr['name'];
	}
	if (isset($embed->{'discriminator-map'})) {
	foreach ($embed->{'discriminator-map'}->{'discriminator-mapping'} as $discriminatorMapping) {
	$attr = $discriminatorMapping->attributes();
	$mapping['discriminatorMap'][(string) $attr['value']] = (string) $attr['class'];
	}
	}
	if (isset($embed->{'default-discriminator-value'})) {
	$mapping['defaultDiscriminatorValue'] = (string) $embed->{'default-discriminator-value'}['value'];
	}
	if (isset($attributes['not-saved'])) {
	$mapping['notSaved'] = ((string) $attributes['not-saved'] === 'true');
	}
	if (isset($attributes['also-load'])) {
	$mapping['alsoLoadFields'] = explode(',', $attributes['also-load']);
	}
	$this->addFieldMapping($class, $mapping);
	}

Expected behavior

If the nullable attribute is set to true to an embedded document property, the ClassMetadata->isNullable() must returns true.

[malarzm]

@wuchen90 thanks for the report! Would you be up for fixing the issue? Taking a look at the XML driver it seems to me that nullable is not handled not only for embed one/many but also for normal fields and references. It'd be great to investigate this all and fix if I'm right.

[wuchen90]

@malarzm
Here is my PR: #2297.
You were right about normal fields and references.