[13.x] Support attribute inheritance for Broadcasting configuration in BroadcastsEvents

[niduranga]

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Currently, models using the BroadcastsEvents trait rely on class properties (e.g., $broadcastConnection, $broadcastQueue) or methods to define their broadcasting configuration. While Laravel has introduced Attribute-based configurations for other Eloquent features, Broadcasting lacked a dedicated attribute.

Furthermore, configuration defined on a BaseModel was not inherited by child models because the trait's reflection logic did not account for the inheritance chain.

Proposed Changes

1. New Attribute: Introduced Illuminate\Database\Eloquent\Attributes\BroadcastsEvents to allow configuring connection, queue, and afterCommit via PHP 8 attributes.
2. Inheritance Support: Updated the BroadcastsEvents trait to use Reflector::getClassAttribute() with ascend: true. This ensures that broadcasting settings defined on a parent class are automatically respected by all child models.
3. Reflector Integration: Optimized the trait to resolve attributes using static::class to ensure reliable reflection during the inheritance lookup.

Benefits

• DRY Principle: Define broadcasting configurations once in a base model instead of repeating properties in every child model.
• Modern Syntax: Provides a declarative way to configure broadcasting, consistent with #[ObservedBy] and #[ScopedBy].

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Example Usage

use Illuminate\Database\Eloquent\Attributes\BroadcastsEvents;

#[BroadcastsEvents(connection: 'redis', queue: 'high-priority', afterCommit: true)]
abstract class BaseModel extends Model
{
    use BroadcastsEvents;
}

class Order extends BaseModel
{
    // Automatically inherits broadcasting settings from BaseModel.
}

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Testing

I have added an integration test in DatabaseEloquentBroadcastingTest.php to verify that:

• The new #[BroadcastsEvents] attribute is correctly resolved.
• Configuration is properly inherited from parent classes via the reflection ascend parameter.

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