Allow each `DataObject` subclass to define its own formfield when autoscaffolded from relation about silverstripe-framework

[mooror]

This would be a marvelous addition to the DataObject infrastructure 💯

[maxime-rainville]

DBField can scaffold form field to manage what should be used to managed them. e.g.

silverstripe-framework/src/ORM/FieldType/DBMoney.php

Lines 184 to 188 in 4429a49

	public function scaffoldFormField($title = null, $params = null)
	{
	return MoneyField::create($this->getName(), $title)
	->setLocale($this->getLocale());
	}

HasOne relation use the DBForeignKey to scaffold their field which builds a SearchableDropdownField for most DataObject. It also has a bit of hard coded logic for File.

silverstripe-framework/src/ORM/FieldType/DBForeignKey.php

Lines 57 to 86 in 4429a49

	public function scaffoldFormField($title = null, $params = null)
	{
	if (empty($this->object)) {
	return null;
	}
	$relationName = substr($this->name ?? '', 0, -2);
	$hasOneClass = DataObject::getSchema()->hasOneComponent(get_class($this->object), $relationName);
	if (empty($hasOneClass)) {
	return null;
	}
	$hasOneSingleton = singleton($hasOneClass);
	if ($hasOneSingleton instanceof File) {
	$field = Injector::inst()->create(FileHandleField::class, $relationName, $title);
	if ($hasOneSingleton instanceof Image) {
	$field->setAllowedFileCategories('image/supported');
	}
	if ($field->hasMethod('setAllowedMaxFileNumber')) {
	$field->setAllowedMaxFileNumber(1);
	}
	return $field;
	}
	$labelField = $hasOneSingleton->hasField('Title') ? 'Title' : 'Name';
	$list = DataList::create($hasOneClass);
	$threshold = self::config()->get('dropdown_field_threshold');
	$overThreshold = $list->count() > $threshold;
	$field = SearchableDropdownField::create($this->name, $title, $list, $labelField)
	->setIsLazyLoaded($overThreshold)
	->setLazyLoadLimit($threshold);
	return $field;
	}

They are many scenarios where SearchableDropdownField is not the best form field to use for a specific DataObject. e.g.: Link, SiteTree, Taxanomie Tags.

I'm thinking it would be trivial to update DBForeignKey::scaffoldFormField() to call a matching scaffoldFormField on singleton to retrieve its form field:

• DataObject::scaffoldFormField() could SearchableDropdownField as a sensible default.
• File could override that default to return an UploadField which would avoid tying DBForeignKey to the File class.
• Specialised DataObjects like Link can specify their own custom field.

Related issues

• #8482
• #11071

[emteknetnz]

Linked PRs have been merged