PropertySchemaCollectionRestriction generates invalid OpenAPI schema

[lstrojny]

API Platform version(s) affected: main

Description
When PropertySchemaCollectionRestriction fails to identify nested constraint restrictions the generated OpenAPI schema might be invalid.

How to reproduce
Given this validation rule:

<property name="someArray">
  <constraint name="Collection">
    <option name="fields">
      <value key="someField">
        <constraint name="Optional">
          <constraint name="SomeConstraintWithoutMatchingRestriction"/>
        </constraint>
      </value>
    </option>
  </constraint>
</property>

The generated schema will look like this:

"Schema": {
  "type": "object",
  "properties": {
    "someArray": {
      "type": "object",
      "properties": {
        "someField": [],
      },
      "additionalProperties": false,
      "items": {
        "type": "string"
      }
   }
  }
}

The issue here is that someField is an empty array but should be an empty object.

[soyuka]

isn't that related to #5414?

[lstrojny]

Related but still different. It is very much possible, that the collection restriction cannot come up with a set of validators, even if #5414 gets fixed. For that case we need to use ArrayObject somewhere (where?) to avoid empty arrays.