feat: add support for conditional execution of migrations

Signed-off-by: Bart Jaskulski <bjaskulski@protonmail.com>

src/AbstractMigration.php

@@ -20,5 +20,12 @@ abstract class AbstractMigration {
 
 	abstract public function up(): bool;
 
-	public function down(): void {}
+	/**
+	 * Allow to skip migration if it is not needed. Tracking of migration version just by wp_options
+	 * value may be subject to random issues, so as a backup, this method can be used to avoid
+	 * errornous migrations like creating alredy exising columns.
+	 */
+	public function is_needed(): bool {
+		return true;
+	}
 }

src/WpdbMigrator.php

@@ -133,7 +133,12 @@ class WpdbMigrator implements Migrator {
 
 				$this->logger->info( sprintf( 'DB update %s:%s', $current_version, $migration->get_version() ) );
 
+				$success = null;
+				if ( $migration->get_migration()->is_needed() ) {
 					$success = $migration->get_migration()->up();
+				} else {
+					$success = true;
+				}
 
 				if ( $success ) {
 					$this->logger->info( sprintf( 'DB update %s:%s -> ', $current_version, $migration->get_version() ) . 'OK' );