fix: return deleted models that have relations

[jaulz]

• Added or updated tests
• Documented user facing changes
• Updated CHANGELOG.md

Changes

Right now, it's not possible to return deleted models and query relations at the same time. For example, when running a mutation that deletes a model I would like to still return the model that was just deleted but if any of its relations is queried as well it will run into an exception, e.g.:

Error: Call to a member function getAttributes() on null in /app/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Collection.php:96
Stack trace:
#0 /app/vendor/laravel/framework/src/Illuminate/Database/Eloquent/Collection.php(119): Illuminate\Database\Eloquent\Collection->loadAggregate(Array, '*', 'count')
#1 /app/vendor/nuwave/lighthouse/src/Execution/ModelsLoader/CountModelsLoader.php(18): Illuminate\Database\Eloquent\Collection->loadCount(Array)
#2 /app/vendor/nuwave/lighthouse/src/Execution/BatchLoader/RelationBatchLoader.php(68): Nuwave\Lighthouse\Execution\ModelsLoader\CountModelsLoader->load(Object(Illuminate\Database\Eloquent\Collection))
#3 /app/vendor/nuwave/lighthouse/src/Execution/BatchLoader/RelationBatchLoader.php(49): Nuwave\Lighthouse\Execution\BatchLoader\RelationBatchLoader->resolve()
#4 /app/vendor/webonyx/graphql-php/src/Executor/Promise/Adapter/SyncPromise.php(63): Nuwave\Lighthouse\Execution\BatchLoader\RelationBatchLoader->Nuwave\Lighthouse\Execution\BatchLoader\{closure}()

This PR serves as a draft and is open to discussion how to handle for example the following cases:

• Shall we return null or 0 on related counts?
• Shall we return null or empty array on related collections?

Breaking changes

tbd

[spawnia]

I would like to still return the model that was just deleted

Why though? I am starting to doubt if Lighthouse should do that.

[jaulz]

I guess you are right... I had that REST pattern in mind that you return the entity that you deleted so you can restore it afterwards. With GraphQL we could potentially run the query to read it before the mutation happens in the same request.