Nullable embedded documents not initialized

[p-golovin]

Bug Report

Q	A
BC Break	no
Version	2.4.2

Summary

Problem is quite similar to #2301, but we try to configure not with xml, but with attributes.

Current behavior

class Publication
{
    #[ODM\EmbedOne(targetDocument: Image::class, nullable: true)]
    private ?Image $image;

    public function getImage(): ?Image
    {
        return $this->image;
    }
}

class Image
{
    #[ODM\Field]
    private string $url;

    public function getUrl(): string
    {
        return $this->url;
    }
}

On loading document without Image subdocument we get error
Typed property Publication::$image must not be accessed before initialization
on request
$pub->getImage();

Expected behavior

Get null.

[malarzm]

but we try to configure not with xml, but with attributes.

I don't think this is related as nothing mapping related changed in #2302. I'd rather guess that your document has no null field stored in the database?

[p-golovin]

We tried both cases:

1. Without null stored in database.
   Get error.

2. With null stored in database.
   Get no error in case of requesting full field 'image' in query builder projection:
   $qb->select('title', 'pub_date', 'image')
   And get error in case of requesting 'image.url' subfield:
   $qb->select('title', 'pub_date', 'image.url')

I think, that field need to be initialised with null even in case of absence in database document (In case we embed collection of documents, it is initialised with empty collection in any case, even if there is no such key in database). Or there are another ways to deal with this?

[malarzm]

Or there are another ways to deal with this?

Try making null a default value: private ?Image $image = null;. That way the field will be initialized with null even though ODM didn't hydrate the field.

With null stored in database. [...] And get error in case of requesting 'image.url' subfield:

Is the error coming from hydration as well?

[p-golovin]

1. In case of storing null in database and use 'image' in projection:
   
   All works at this point. But there is problem with document serialisation: we get 'image': null in json instead of absence image field.

2. In case of storing null in database and using 'image.url' in projection:
   
   No errors on hydration, but no 'image' field in document. So error Typed property Publication::$image must not be accessed before initialisation.

3. If we use private ?Image $image = null; then we have field in serialised document again:
   
   We can solve this with options of serialisation context.

So only question with projection is actual.

[malarzm]

In case of storing null in database and using 'image.url' in projection:

Using 3 should still make projection "work" as the image will be initialized to null, no? Generally speaking if there's no image object in stored document projection will not return it. Same goes for null:

> db.test.find();
{ "_id" : ObjectId("62faa4f3417246422135f933"), "name" : "Withembed", "embed" : { "test" : "aaa" } }
{ "_id" : ObjectId("62faa50d417246422135f934"), "name" : "Noembed" }
{ "_id" : ObjectId("62faa589417246422135f935"), "name" : "Nulled", "embed" : null }
> db.test.find({}, {"name": 1, "embed.test": 1});
{ "_id" : ObjectId("62faa4f3417246422135f933"), "name" : "Withembed", "embed" : { "test" : "aaa" } }
{ "_id" : ObjectId("62faa50d417246422135f934"), "name" : "Noembed" }
{ "_id" : ObjectId("62faa589417246422135f935"), "name" : "Nulled" }

[p-golovin]

Thank you! This works well.