Add process plugin to generate unique array.

src/Plugin/migrate/process/ArrayUnique.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Drupal\up_migrate\Plugin\migrate\process;
+
+use Drupal\migrate\MigrateExecutableInterface;
+use Drupal\migrate\ProcessPluginBase;
+use Drupal\migrate\Row;
+
+/**
+ * This plugin removes duplicate values from source value.
+ *
+ * @MigrateProcessPlugin(
+ * id = "array_unique",
+ * handle_multiples = TRUE
+ * )
+ */
+class ArrayUnique extends ProcessPluginBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
+ if (!is_array($value)) {
+ $value = [$value];
+ }
+ return array_unique($value);
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function multiple() {
+ return TRUE;
+ }
+
+}