Saving records with a given uuid - cakephp

Question

I want to save a bunch of static records in my database with a given uuid, this is for testing purposes, so that on every system the application starts with the exact same dataset.
When inserting with SQL this is no problem but I wanted to use the CakePHP way ( I use a migrations file for this, but that does not matter).
The problem is that I give cake a data array like this and save it:
$data = [
['id' => '5cedf79a-e4b9-f235-3d4d-9fbeef41c7e8', 'name' => 'test'],
['id' => 'c2bf879c-072c-51a4-83d8-edbf2d97e07e', 'name' => 'test2']
];
$table = TableRegistry::get('My_Model');
$entities = $table->newEntities($data, [
'accessibleFields' => ['*' => true],
'validate' => false
]);
array_map([$table, 'save'], $entities );
Everything saves, but all my items have been given a different uuid, If I debug a record after saving it shows the original uuid in the entity
'new' => false,
'accessible' => [
'*' => true
],
'properties' => [
'id' => '6b4524a8-4698-4297-84e5-5160f42f663b',
'name' => 'test',
],
'dirty' => [],
'original' => [
'id' => '5cedf79a-e4b9-f235-3d4d-9fbeef41c7e8'
],
So why does cake generate a new uuid for me? and how do I prevent it

Answer 1

This doesn't work because primary keys are unconditionally being generated before the insert operation, see
https://github.com/cakephp/cakephp/blob/3.0.0/src/ORM/Table.php#L1486-L1490
// ...
$id = (array)$this->_newId($primary) + $keys;
$primary = array_combine($primary, $id);
$filteredKeys = array_filter($primary, 'strlen');
$data = $filteredKeys + $data;
// ...
$statement = $this->query()->insert(array_keys($data))
->values($data)
->execute();
// ...
Currently the UUID type is the only type that implements generating IDs, so providing custom IDs works with other types.
You can workaround this by for example overriding the _newId() method in your table so that it returns null, which effectively results in the existing primary key not being overwritten.
protected function _newId($primary)
{
// maybe add some conditional logic here
// in case you don't want to be required
// to always manually provide a primary
// key for your insert operations
return null;
}