[12.x] Add whereAttachedTo() Eloquent builder method

[bakerkretzmar]

This PR adds a whereAttachedTo() Eloquent query builder method to simplify retrieving records that are 'attached' to a given model instance/collection with a belongsToMany relationship.

It functions very similarly to the whereBelongsTo() method introduced in #38927, and eliminates the need to pass a closure to whereHas and/or extract the parent model ID(s) manually.

Given some models:

$tags = Tag::where('created_at', '>', now()->subMonth())->get();

Before

$taggedPosts = Post::whereHas('tags', function ($query) use ($tags) {
    $query->whereKey($tags);
})->get();

After

$taggedPosts = Post::whereAttachedTo($tags)->get();

Like whereBelongsTo(), whereAttachedTo() guesses the relationship name based on Laravel conventions, but it can also be passed in manually:

$taggedPosts = Post::whereAttachedTo($tags, 'tags')->get();

Couple last things:

• I know in the specific example above the conditions could be written directly into a has query, but that isn't always practical if they change based on other variables or if the parent model/collection is used in other places.
• This method includes results attached to any of the models passed into it, which feels like a more common use case to me, but this could also be called whereAttachedToAny() to be more specific and leave room for a later whereAttachedToAll().

Thanks!

[taylorotwell]

Thanks!

[robsontenorio]

@bakerkretzmar on your example “whereKey(…)” it is the same as “whereIn(….)” ?

[bakerkretzmar]

In this case it's more or less the same yeah:

framework/src/Illuminate/Database/Eloquent/Builder.php

Lines 260 to 281 in db293d9

	public function whereKey($id)
	{
	if ($id instanceof Model) {
	$id = $id->getKey();
	}
	if (is_array($id) || $id instanceof Arrayable) {
	if (in_array($this->model->getKeyType(), ['int', 'integer'])) {
	$this->query->whereIntegerInRaw($this->model->getQualifiedKeyName(), $id);
	} else {
	$this->query->whereIn($this->model->getQualifiedKeyName(), $id);
	}
	return $this;
	}
	if ($id !== null && $this->model->getKeyType() === 'string') {
	$id = (string) $id;
	}
	return $this->where($this->model->getQualifiedKeyName(), '=', $id);
	}