handleLazyLoadingViolation shouldn't throw for newly created model instances

[rogatty]

• Laravel Version: 9.1.0
• PHP Version: 8.1.3
• Database Driver & Version: N/A

Description:

framework/src/Illuminate/Database/Eloquent/Concerns/HasAttributes.php

Lines 517 to 524 in 91c60ea

	protected function handleLazyLoadingViolation($key)
	{
	if (isset(static::$lazyLoadingViolationCallback)) {
	return call_user_func(static::$lazyLoadingViolationCallback, $this, $key);
	}
	throw new LazyLoadingViolationException($this, $key);
	}

HasAttributes::handleLazyLoadingViolation shouldn't throw LazyLoadingViolationException if model instance was created in memory, and not fetched from the database. It's impossible to eager load relations for a model that doesn't exist yet. Throwing an exception in this scenario doesn't prevent unnecessary database queries and requires manual bypassing.

I solved it by adding the following to AppServiceProvider:

Model::handleLazyLoadingViolationUsing(
	static function (Model $model, string $relation) {
		// It's fine that you didn't eager load relations for a new model as it wouldn't make sense
		if (!$model->exists || $model->wasRecentlyCreated) {
			return;
		}

		throw new LazyLoadingViolationException($model, $relation);
	}
);

I believe this condition should be built into HasAttributes::handleLazyLoadingViolation.

Steps To Reproduce:

Fixed by checking !$model->exists:

$model = ParentModel::make();
$childModel = ChildModel::make();
$model->children->push($childModel);

Fixed by checking $model->wasRecentlyCreated:

$model = Model::make();
$model->save();
$model->children->each(
	function (ChildModel $child) {
		$child->parent_id = $model->id;
		$child->save();
	}
);

!$model->exists isn't enough in the second case because relation wasn't initialized before saving the model.

Why I bumped into this issue:

I expect the question "why do you use relations like that?" so let me answer upfront. I'm trying to use a DDD approach where the operations are split into stages (simplified):

• Load models from database
• Modify models – make new children instances and push them to relation collection (or not, depends on request data)
• Persist models to database - iterate over relation collection items, set the parent ID and save to database

[driesvints]

Heya, yes this seems reasonable to us. Can you send in a PR?