fix: ArrayDescriber splitting arrayKey() union into anyOf [array, object]

[gnutix]

Problem

When Symfony's TypeInfo resolves array<T> (single generic parameter, no explicit key type), the key defaults to arrayKey() — a union(int, string). ArrayDescriber splits this into separate array<int, T> and array<string, T> types, producing an incorrect OpenAPI schema:

{
  "anyOf": [
    { "type": "array", "items": { "$ref": "#/components/schemas/MyDto" } },
    { "type": "object", "additionalProperties": { "$ref": "#/components/schemas/MyDto" } }
  ]
}

The correct output should be just { "type": "array", "items": { "$ref": "#/components/schemas/MyDto" } }, since array<T> in PHP — especially in the context of JSON API responses — means a sequential array (JSON array), not "either array or object".

Traversable objects as generic parameters

When a Traversable object is used as a generic parameter (e.g. list<MyIterableClass>), StringTypeResolver wraps it in CollectionType(ObjectType) with no key/value type info. ArrayDescriber then describes this as array<unknown> (because getCollectionValueType() returns mixed()), losing the type reference entirely.

The fix detects when the wrapped type is an ObjectType (meaning StringTypeResolver auto-wrapped a Traversable class) and delegates to the chain so ClassDescriber can create a proper $ref.

Reproduction

final class EventDTO
{
    /** @var RefereeDTO[] */
    public array $referees;
}

With type_info: true (Symfony ≥ 7.3), the referees property schema includes both array and object types instead of just array.

Relation to #2508

Issue #2508 reported two symptoms:

1. type_info: false: "items": {} (empty, no type info) — this was caused by ConstructorExtractor not reading @var on promoted constructor properties, and was fixed upstream in Symfony 7.4 ([Serialization] with_constructor_extractor: true - @var docs on promoted properties ignored symfony/symfony#60795).
2. type_info: true: "oneOf": [{ "type": "array" }, { "type": "object" }] — this is the ArrayDescriber issue fixed by this PR. Even with Symfony 7.4, once TypeInfo correctly reads the type, ArrayDescriber still splits the arrayKey() union into anyOf: [array, object].

This PR fixes the remaining symptom 2 from #2508.

[Copilot]

Pull request overview

This PR fixes how ArrayDescriber handles Symfony TypeInfo collection key unions so that array<T> (with the implicit arrayKey(): int|string key) is described as a JSON array rather than being split into an OpenAPI anyOf/oneOf of [array, object]. It also improves handling of Traversable objects that TypeInfo auto-wraps as collections, ensuring object references aren’t lost.

Changes:

• Treat arrayKey() (int|string) key unions as a list/JSON array instead of splitting into separate keyed array types.
• Unwrap CollectionType(ObjectType) cases (auto-wrapped Traversable objects) and delegate directly so the $ref can be produced.
• Add PHPUnit coverage for both behaviors.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/TypeDescriber/ArrayDescriber.php	Adds special-casing for arrayKey() unions and unwraps Traversable object collections to preserve $ref types.
tests/TypeDescriber/ArrayDescriberTest.php	Adds tests to validate list handling for arrayKey() unions and unwrapping behavior for Traversable objects.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.41%. Comparing base (7f69a49) to head (f8a616a).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##              5.x    #2704      +/-   ##
==========================================
- Coverage   95.59%   95.41%   -0.18%     
==========================================
  Files          94       94              
  Lines        3064     3078      +14     
==========================================
+ Hits         2929     2937       +8     
- Misses        135      141       +6     

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