fixed date field migration on projet_node

web/modules/custom/migrate_leshed/config/install/migrate_plus.migration.projet_node.yml

@@ -63,15 +63,13 @@ process:
     default_value: projet
   title: title
   field_dates/value:
-    plugin: format_date
+    plugin: leshed_date
     source: date_start
-    from_format: 'd/m/Y'
-    to_format: 'Y-m-d'
   field_dates/end_value:
-    plugin: format_date
+    plugin: leshed_date
     source: date_end
-    from_format: 'd/m/Y'
-    to_format: 'Y-m-d'
+    end_of_year: true
+    fallback_source: date_start
   field_type_de_projet:
     -
       plugin: skip_on_empty

web/modules/custom/migrate_leshed/src/Plugin/migrate/process/LeshedDate.php

@@ -0,0 +1,77 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Drupal\migrate_leshed\Plugin\migrate\process;
+
+use Drupal\migrate\Attribute\MigrateProcess;
+use Drupal\migrate\MigrateExecutableInterface;
+use Drupal\migrate\ProcessPluginBase;
+use Drupal\migrate\Row;
+
+/**
+ * Converts Google Sheet project dates to 'Y-m-d'.
+ *
+ * Accepted inputs:
+ * - 'd/m/Y' (e.g. "19/09/2015"),
+ * - a bare year (e.g. "2016"), converted to the first day of the year, or
+ *   to the last day when 'end_of_year: true' is set in the configuration.
+ *
+ * When the value is empty or invalid and 'fallback_source' is set in the
+ * configuration, the named source property is converted instead. This is
+ * used to default the end date to the start date, since the daterange
+ * field requires a non-null end value.
+ *
+ * Invalid or unparseable values return NULL and are logged in the
+ * migration messages instead of failing the whole row.
+ */
+#[MigrateProcess(id: 'leshed_date')]
+final class LeshedDate extends ProcessPluginBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property): ?string {
+    $result = $this->convert($value, $migrate_executable, $destination_property);
+
+    if ($result === NULL && !empty($this->configuration['fallback_source'])) {
+      $fallback = $row->getSourceProperty($this->configuration['fallback_source']);
+      $result = $this->convert($fallback, $migrate_executable, $destination_property);
+    }
+
+    return $result;
+  }
+
+  /**
+   * Converts a single raw value to 'Y-m-d', or NULL if not parseable.
+   */
+  private function convert(mixed $value, MigrateExecutableInterface $migrate_executable, string $destination_property): ?string {
+    if (!is_string($value)) {
+      return NULL;
+    }
+    $value = trim($value);
+    if ($value === '') {
+      return NULL;
+    }
+
+    // Bare year: "2016".
+    if (preg_match('/^\d{4}$/', $value)) {
+      return empty($this->configuration['end_of_year'])
+        ? $value . '-01-01'
+        : $value . '-12-31';
+    }
+
+    // Full date: "19/09/2015".
+    $date = \DateTime::createFromFormat('!d/m/Y', $value);
+    $errors = \DateTime::getLastErrors();
+    if ($date === FALSE || ($errors && ($errors['warning_count'] || $errors['error_count']))) {
+      $migrate_executable->saveMessage(
+        sprintf('Date invalide "%s" pour la propriété "%s".', $value, $destination_property)
+      );
+      return NULL;
+    }
+
+    return $date->format('Y-m-d');
+  }
+
+}