--- /dev/null
+<?php
+
+namespace Drupal\comment\Plugin\migrate\source\d6;
+
+use Drupal\migrate\Row;
+use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;
+
+/**
+ * Drupal 6 comment source from database.
+ *
+ * @MigrateSource(
+ * id = "d6_comment",
+ * source_provider = "comment"
+ * )
+ */
+class Comment extends DrupalSqlBase {
+
+ /**
+ * {@inheritdoc}
+ */
+ public function query() {
+ $query = $this->select('comments', 'c')
+ ->fields('c', ['cid', 'pid', 'nid', 'uid', 'subject',
+ 'comment', 'hostname', 'timestamp', 'status', 'thread', 'name',
+ 'mail', 'homepage', 'format']);
+ $query->innerJoin('node', 'n', 'c.nid = n.nid');
+ $query->fields('n', ['type']);
+ $query->orderBy('c.timestamp');
+ return $query;
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function prepareRow(Row $row) {
+ if ($this->variableGet('comment_subject_field_' . $row->getSourceProperty('type'), 1)) {
+ // Comment subject visible.
+ $row->setSourceProperty('field_name', 'comment');
+ $row->setSourceProperty('comment_type', 'comment');
+ }
+ else {
+ $row->setSourceProperty('field_name', 'comment_no_subject');
+ $row->setSourceProperty('comment_type', 'comment_no_subject');
+ }
+ // In D6, status=0 means published, while in D8 means the opposite.
+ // See https://www.drupal.org/node/237636.
+ $row->setSourceProperty('status', !$row->getSourceProperty('status'));
+ return parent::prepareRow($row);
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function fields() {
+ return [
+ 'cid' => $this->t('Comment ID.'),
+ 'pid' => $this->t('Parent comment ID. If set to 0, this comment is not a reply to an existing comment.'),
+ 'nid' => $this->t('The {node}.nid to which this comment is a reply.'),
+ 'uid' => $this->t('The {users}.uid who authored the comment. If set to 0, this comment was created by an anonymous user.'),
+ 'subject' => $this->t('The comment title.'),
+ 'comment' => $this->t('The comment body.'),
+ 'hostname' => $this->t("The author's host name."),
+ 'timestamp' => $this->t('The time that the comment was created, or last edited by its author, as a Unix timestamp.'),
+ 'status' => $this->t('The published status of a comment. (0 = Published, 1 = Not Published)'),
+ 'format' => $this->t('The {filter_formats}.format of the comment body.'),
+ 'thread' => $this->t("The vancode representation of the comment's place in a thread."),
+ 'name' => $this->t("The comment author's name. Uses {users}.name if the user is logged in, otherwise uses the value typed into the comment form."),
+ 'mail' => $this->t("The comment author's email address from the comment form, if user is anonymous, and the 'Anonymous users may/must leave their contact information' setting is turned on."),
+ 'homepage' => $this->t("The comment author's home page address from the comment form, if user is anonymous, and the 'Anonymous users may/must leave their contact information' setting is turned on."),
+ 'type' => $this->t("The {node}.type to which this comment is a reply."),
+ ];
+ }
+
+ /**
+ * {@inheritdoc}
+ */
+ public function getIds() {
+ $ids['cid']['type'] = 'integer';
+ return $ids;
+ }
+
+}