Query dump

hacky final solution without reset query

/**
 * Group messages by thread id pulling message and thread ids from the provided $queryScopes Query object
 *
 * @param QueryBuilder $query QueryBuilder object to apply the scope to
 * @param QueryBuilder $queryScopes QueryBuilder object to use to get the message ids from
 * @return QueryBuilder $query
 */
public function scopeGroupedByThread($query, $queryScopes = null)
{
    $queryScopes = $queryScopes ?: $this->newQuery();
    return $query->whereIn('id', array_values($queryScopes->lists('id', 'thread_id')));
}

public function scopeLatestReceivedGroupedByThread($query)
{
    return $query
        ->groupedByThread((clone $query)
            ->received()
            // Force getting via oldest first because the lsat item will be as the containing item by groupedByThread
            ->removeOrder('sent_at')
            ->oldest())
        // Reorder the now grouped messages to get the desired order
        ->removeOrder('sent_at')
        ->newest();
}

hacky groupBy.php

public function scopeGroupedByThread($query)
{
    $scopeIds = array_values($query->lists('id', 'thread_id'));
    return $query->resetQuery()->whereIn('id', $scopeIds);
}

public function scopeLatestReceivedGroupedByThread($query)
{
    return $query
        ->received()
        // Force getting via oldest first because the lsat item will be as the containing item by groupedByThread
        ->removeOrder('sent_at')
        ->oldest()
        ->groupedByThread()
        // Reorder the now grouped messages to get the desired order
        ->removeOrder('sent_at')
        ->newest();
}

initial combined methods

public function scopeLatestReceivedGroupedByThread($query)
{
    $groupedQuery = clone $query;
    // Get the message ids to display flattened by groups, get by oldest first because the last item added to the thread_id key returned by lists
    // will be the only one in that array element.
    $groupedMessageIds = array_values($groupedQuery->received()->removeOrder('sent_at')->oldest()->lists('id', 'thread_id'));
    
    // Get all messages in the previously selected array of ids, sort by newest this time
    return $query->whereIn('id', $groupedMessageIds)->removeOrder('sent_at')->newest();
}