Osm Admin: New Approach To Migrations

I continued working on property diff algorithm that plans all the migration details.

Contents:

• Main Idea
• Property::diff()
• Property::explicit()

Main Idea

The refactoring idea is to:

1. Compare property attributes in Property::diff(), and to register various callbacks along the way.
2. During migration and conversion, execute all registered callbacks.

Property::diff()

Again, just as previous Migration classes, the Property::diff() method compares individual property attributes:

// Osm\Admin\Schema\Diff\Property\Int_
public function diff(): void {
    $this->explicit();
    $this->type();
    $this->nullable();
    $this->size();
    $this->unsigned();
    $this->autoIncrement();
}

// Osm\Admin\Schema\Diff\Property\String_
public function diff(): void {
    $this->explicit();
    $this->type();
    $this->nullable();
    $this->size();
    $this->length();
}

Property::explicit()

This method checks if the property is brand new, if it becomes explicit, or, on the contrary, if it becomes implicit and "orders" needed migrations and data conversions:

protected function explicit(): void {
    $this->attribute('explicit', function() {
        if ($this->new->explicit) {
            if ($this->old) {
                if (!$this->old->explicit) {
                    $this->createColumn();
                    $this->convert();
                    $this->dropJson();
                }
            }
            else {
                $this->createColumn();
            }

        }
        else { // !$this->new->explicit
            if ($this->old?->explicit) {
                $this->convert();
                $this->dropColumn();
            }
        }
    });
}

The createColumn(), convert() and other helper methods used here basically just set some boolean flags and register callbacks to be processed later during the migration phase.