ManyManyThroughList join record flags all fields as changed

[kinglozzer]

Affects 4.x and 5.x

When saving changes to a join record in a many-many-through relation, DataObject::getChangedFields() will report all fields as changed. This is because ManyManyThroughList::createDataObject() creates the join record as though it’s a brand new DataObject, not one that already exists in the database:

silverstripe-framework/src/ORM/ManyManyThroughList.php

Lines 86 to 92 in 9a279f6

	// Create joined record
	if ($joinRow) {
	$joinClass = $this->manipulator->getJoinClass();
	$joinQueryParams = $this->manipulator->extractInheritableQueryParameters($this->dataQuery);
	$joinRecord = Injector::inst()->create($joinClass, $joinRow, false, $joinQueryParams);
	$record->setJoin($joinRecord, $joinAlias);
	}

Using DataObject::CREATE_HYDRATED resolves this:

$joinRecord = Injector::inst()->create($joinClass, $joinRow, DataObject::CREATE_HYDRATED, $joinQueryParams);

PR

• FIX: Stop ManyManyThroughList join records incorrectly showing as changed (fixes #10821) #10923

[GuySartorelli]

Pull request merged. It'll be automatically tagged by GitHub Actions.