reverted:
--- b/core/modules/content_translation/migration_templates/d6_i18n_block.yml
+++ /dev/null
@@ -1,64 +0,0 @@
-id: d6_i18n_block
-label: i18n Blocks
-migration_tags:
-  - Drupal 6
-source:
-  plugin: d6_i18n_block
-  constants:
-    dest_label: 'settings/label'
-process:
-  langcode: language
-  property: constants/dest_label
-  translation: title
-  id:
-    plugin: migration
-    migration: d6_block
-    source:
-      - module
-      - delta
-  plugin:
-    -
-      plugin: static_map
-      bypass: true
-      source:
-        - module
-        - delta
-      map:
-        book:
-          0: book_navigation
-        comment:
-          0: views_block:comments_recent-block_1
-        forum:
-          0: forum_active_block
-          1: forum_new_block
-        locale:
-          0: language_block
-        node:
-          0: node_syndicate_block
-        search:
-          0: search_form_block
-        statistics:
-          0: statistics_popular_block
-        system:
-          0: system_powered_by_block
-        user:
-          0: user_login_block
-          1: system_menu_block:tools
-          2: views_block:who_s_new-block_1
-          3: views_block:who_s_online-who_s_online_block
-    -
-      plugin: block_plugin_id
-    -
-      plugin: skip_on_empty
-      method: row
-  theme:
-    plugin: block_theme
-    source:
-      - theme
-      - default_theme
-      - admin_theme
-destination:
-  plugin: entity:block
-migration_dependencies:
-  required:
-    - d6_block
reverted:
--- b/core/modules/content_translation/migration_templates/d6_i18n_custom_block.yml
+++ /dev/null
@@ -1,27 +0,0 @@
-id: d6_i18n_custom_block
-label: Custom blocks
-migration_tags:
-  - Drupal 6
-source:
-  plugin: d6_i18n_box
-  constants:
-    type: basic
-process:
-  id: bid
-  langcode: language
-  type: 'constants/type'
-  info: info
-  'body/format':
-    plugin: migration
-    migration: d6_filter_format
-    source: format
-  'body/value': body
-destination:
-  plugin: entity:block_content
-  no_stub: true
-  translations: true
-migration_dependencies:
-  required:
-    - d6_filter_format
-    - block_content_body_field
-    - d6_custom_block
reverted:
--- b/core/modules/content_translation/src/Plugin/migrate/source/d6/I18nBlock.php
+++ /dev/null
@@ -1,104 +0,0 @@
-<?php
-
-namespace Drupal\content_translation\Plugin\migrate\source\d6;
-
-use Drupal\migrate\Row;
-use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;
-
-/**
- * Gets i18n block data from source database.
- *
- * @MigrateSource(
- *   id = "d6_i18n_block",
- *   source_provider = "block"
- * )
- */
-class I18nBlock extends DrupalSqlBase {
-
-  /**
-   * The default theme name.
-   *
-   * @var string
-   */
-  protected $defaultTheme;
-
-  /**
-   * The admin theme name.
-   *
-   * @var string
-   */
-  protected $adminTheme;
-
-  /**
-   * Table containing block configuration.
-   *
-   * @var string
-   */
-  protected $blockTable;
-
-  /**
-   * {@inheritdoc}
-   */
-  public function query() {
-    if ($this->getModuleSchemaVersion('system') >= 7000) {
-      $this->blockTable = 'block';
-    }
-    else {
-      $this->blockTable = 'blocks';
-    }
-
-    $query = $this->select('i18n_blocks', 'i18n')
-      ->fields('i18n', ['ibid', 'module', 'delta', 'type', 'language'])
-      ->fields('b', ['bid', 'module', 'delta', 'theme', 'title']);
-    $query->addField('b', 'module', 'block_module');
-    $query->addField('b', 'delta', 'block_delta');
-    $query->leftJoin($this->blockTable, 'b', ('b.module = i18n.module AND b.delta = i18n.delta'));
-    return $query;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function initializeIterator() {
-    $this->defaultTheme = $this->variableGet('theme_default', 'Garland');
-    $this->adminTheme = $this->variableGet('admin_theme', NULL);
-    return parent::initializeIterator();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function fields() {
-    return [
-      'bid' => $this->t('The block numeric identifier.'),
-      'module' => $this->t('The module providing the block.'),
-      'delta' => $this->t("The block's delta."),
-      'title' => $this->t("Title translation for this language.."),
-      'theme' => $this->t('Which theme the block is placed in.'),
-      'language' => $this->t('Language for this field.'),
-    ];
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getIds() {
-    $ids['module']['type'] = 'string';
-    $ids['module']['alias'] = 'b';
-    $ids['delta']['type'] = 'string';
-    $ids['delta']['alias'] = 'b';
-    $ids['theme']['type'] = 'string';
-    $ids['language']['type'] = 'string';
-    return $ids;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function prepareRow(Row $row) {
-    $row->setSourceProperty('default_theme', $this->defaultTheme);
-    $row->setSourceProperty('admin_theme', $this->adminTheme);
-    return parent::prepareRow($row);
-  }
-
-}
reverted:
--- b/core/modules/content_translation/src/Plugin/migrate/source/d6/I18nBox.php
+++ /dev/null
@@ -1,103 +0,0 @@
-<?php
-
-namespace Drupal\content_translation\Plugin\migrate\source\d6;
-
-use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;
-
-/**
- * Gets Drupal 6 i18n custom block translations from database.
- *
- * @MigrateSource(
- *   id = "d6_i18n_box"
- * )
- */
-class I18nBox extends DrupalSqlBase {
-
-  const INFO = "CASE WHEN property = 'title' THEN translation ELSE info END";
-  const BODY = "CASE WHEN property = 'body' THEN translation ELSE body END";
-
-  /**
-   * {@inheritdoc}
-   */
-  public function count() {
-    return $this->initializeIterator()->count();
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function initializeIterator() {
-    return new \ArrayIterator($this->values());
-  }
-
-  /**
-   * Merge the block body and info translations into a single row.
-   *
-   * @return array
-   *   An array of ...
-   */
-  protected function values() {
-    $values = [];
-    $result = $this->prepareQuery()->execute()->FetchAll();
-    $cnt = count($result);
-    for ($i = 0; $i < $cnt; $i++) {
-      if (isset($result[$i])) {
-        $j = $i + 1;
-        if (isset($result[$j])) {
-          // If the same bid and language, then this is the info.
-          if ($result[$i]['bid'] == $result[$j]['bid'] and
-            $result[$i]['language'] == $result[$j]['language']
-          ) {
-            $result[$i]['info'] = $result[$j]['info'];
-            unset($result[$j]);
-          }
-        }
-        $values[] = $result[$i];
-      }
-    }
-    return $values;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function query() {
-    $query = $this->select('i18n_strings', 'i18n')
-      ->fields('i18n', ['lid', 'type', 'property', 'objectid'])
-      ->fields('lt', ['lid', 'language', 'translation'])
-      ->fields('b', ['bid', 'body', 'info', 'format'])
-      ->orderBy('bid')
-      ->orderBy('language')
-      ->orderBy('property')
-      ->condition('i18n.type', 'block');
-    $query->addExpression(self::INFO, 'info');
-    $query->addExpression(self::BODY, 'body');
-    $query->leftJoin('boxes', 'b', 'b.bid = i18n.objectid');
-    $query->leftJoin('locales_target', 'lt', 'lt.lid = i18n.lid');
-
-    return $query;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function fields() {
-    return [
-      'bid' => $this->t('The block numeric identifier.'),
-      'language' => $this->t('Language for this field.'),
-      'body' => $this->t('The block/box content'),
-      'info' => $this->t('Admin title of the block/box.'),
-      'format' => $this->t('Input format of the custom block/box content.'),
-    ];
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getIds() {
-    $ids['bid']['type'] = 'integer';
-    $ids['language']['type'] = 'string';
-    return $ids;
-  }
-
-}
reverted:
--- b/core/modules/content_translation/tests/src/Kernel/Migrate/d6/MigrateI18nBlockContentTest.php
+++ /dev/null
@@ -1,54 +0,0 @@
-<?php
-
-namespace Drupal\Tests\content_translation\Kernel\Migrate\d6;
-
-use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
-
-/**
- * Tests migration of i18n block translations.
- *
- * @group migrate_drupal_6
- */
-class MigrateI18nBlockContentTest extends MigrateDrupal6TestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = [
-    'block',
-    'views',
-    'block_content',
-    'content_translation',
-    'language',
-  ];
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    parent::setUp();
-    $this->installConfig(['block']);
-    $this->installConfig(['block_content']);
-    $this->installEntitySchema('block_content');
-
-    $this->executeMigrations([
-      'd6_filter_format',
-      'block_content_type',
-      'block_content_body_field',
-      'd6_custom_block',
-      'd6_user_role',
-      'd6_block',
-      'd6_i18n_block',
-    ]);
-    block_rebuild();
-  }
-
-  /**
-   * Tests the migration of block title translation.
-   */
-  public function testI18nBlock() {
-    $config = \Drupal::service('language_manager')->getLanguageConfigOverride('zu', 'block.block.user_1');
-    $this->assertSame('zu - Test Title 02', $config->get('settings.label'));
-  }
-
-}
reverted:
--- b/core/modules/content_translation/tests/src/Kernel/Migrate/d6/MigrateI18nCustomBlockContentTest.php
+++ /dev/null
@@ -1,73 +0,0 @@
-<?php
-
-namespace Drupal\Tests\content_translation\Kernel\Migrate\d6;
-
-use Drupal\block_content\Entity\BlockContent;
-use Drupal\language\Entity\ConfigurableLanguage;
-use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
-
-/**
- * Tests migration of i18n custom block strings.
- *
- * @group migrate_drupal_6
- */
-class MigrateI18nCustomBlockContentTest extends MigrateDrupal6TestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = [
-    'block',
-    'block_content',
-    'config_translation',
-    'content_translation',
-    'language',
-  ];
-
-  /**
-   * {@inheritdoc}
-   */
-  protected function setUp() {
-    parent::setUp();
-    $this->installConfig(['block_content']);
-    $this->installEntitySchema('block_content');
-    ConfigurableLanguage::createFromLangcode('en')->save();
-    ConfigurableLanguage::createFromLangcode('fr')->save();
-    ConfigurableLanguage::createFromLangcode('zu')->save();
-    $this->executeMigrations([
-      'd6_filter_format',
-      'block_content_type',
-      'block_content_body_field',
-      'd6_custom_block',
-      'd6_i18n_custom_block',
-    ]);
-  }
-
-  /**
-   * Tests the Drupal 6 i18n custom block strings to Drupal 8 migration.
-   */
-  public function testBlockMigration() {
-    /** @var BlockContent $block */
-    $block = BlockContent::load(1)->getTranslation('fr');
-    $this->assertSame('fr - Static Block', $block->label());
-    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
-    $this->assertSame('fr', $block->language()->getId());
-    $this->assertSame('<h3>fr - My first custom block body</h3>', $block->body->value);
-    $this->assertSame('full_html', $block->body->format);
-
-    $block = BlockContent::load(1)->getTranslation('zu');
-    $this->assertSame('My block 1', $block->label());
-    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
-    $this->assertSame('zu', $block->language()->getId());
-    $this->assertSame('<h3>zu - My first custom block body</h3>', $block->body->value);
-    $this->assertSame('full_html', $block->body->format);
-
-    $block = BlockContent::load(2)->getTranslation('fr');
-    $this->assertSame('Encore un bloc statique', $block->label());
-    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
-    $this->assertSame('fr', $block->language()->getId());
-    $this->assertSame('Nom de vocabulaire beaucoup plus long que trente-deux caractères', $block->body->value);
-    $this->assertSame('full_html', $block->body->format);
-  }
-
-}
reverted:
--- b/core/modules/content_translation/tests/src/Kernel/Plugin/migrate/source/d6/I18nBlockTest.php
+++ /dev/null
@@ -1,100 +0,0 @@
-<?php
-
-namespace Drupal\Tests\content_translation\Kernel\Plugin\migrate\source\d6;
-
-use Drupal\Tests\migrate\Kernel\MigrateSqlSourceTestBase;
-
-/**
- * Tests i18n block title source plugin.
- *
- * @covers Drupal\content_translation\Plugin\migrate\source\d6\I18nBlock
- *
- * @group content_translation
- */
-class I18nBlockTest extends MigrateSqlSourceTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = ['content_translation', 'migrate_drupal'];
-
-  /**
-   * {@inheritdoc}
-   */
-  public function providerSource() {
-    $tests = [];
-
-    // The source data.
-    $tests[0]['source_data']['blocks'] = [
-      [
-        'bid' => 1,
-        'module' => 'user',
-        'delta' => '1',
-        'theme' => 'garland',
-        'status' => 1,
-        'weight' => 0,
-        'region' => 'left',
-        'visibility' => 0,
-        'pages' => '',
-        'title' => 'fr - Test Title 01',
-        'cache' => -1,
-      ],
-      [
-        'bid' => 2,
-        'module' => 'user',
-        'delta' => '2',
-        'theme' => 'garland',
-        'status' => 1,
-        'weight' => 5,
-        'region' => 'right',
-        'visibility' => 0,
-        'pages' => '<front>',
-        'title' => 'zu - Test Title 02',
-        'cache' => -1,
-      ],
-    ];
-
-    $tests[0]['source_data']['i18n_blocks'] = [
-      [
-        'ibid' => 1,
-        'module' => 'user',
-        'delta' => '1',
-        'type' => 0,
-        'language' => 'fr',
-      ],
-      [
-        'ibid' => 2,
-        'module' => 'user',
-        'delta' => '2',
-        'type' => 0,
-        'language' => 'zu',
-      ],
-    ];
-
-    // The expected results.
-    $tests[0]['expected_results'] = [
-      [
-        'bid' => 1,
-        'module' => 'user',
-        'delta' => '1',
-        'title' => 'fr - Test Title 01',
-        'ibid' => 1,
-        'type' => '0',
-        'language' => 'fr',
-      ],
-      [
-        'bid' => 2,
-        'module' => 'user',
-        'delta' => '2',
-        'theme' => 'garland',
-        'title' => 'zu - Test Title 02',
-        'ibid' => 2,
-        'type' => '0',
-        'language' => 'zu',
-      ],
-    ];
-
-    return $tests;
-  }
-
-}
reverted:
--- b/core/modules/content_translation/tests/src/Kernel/Plugin/migrate/source/d6/I18nBoxTest.php
+++ /dev/null
@@ -1,143 +0,0 @@
-<?php
-
-namespace Drupal\Tests\content_translation\Kernel\Plugin\migrate\source\d6;
-
-use Drupal\Tests\migrate\Kernel\MigrateSqlSourceTestBase;
-
-/**
- * Tests i18n block title source plugin.
- *
- * @covers Drupal\content_translation\Plugin\migrate\source\d6\I18nBox
- *
- * @group content_translation
- */
-class I18nBoxTest extends MigrateSqlSourceTestBase {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static $modules = ['content_translation', 'migrate_drupal'];
-
-  /**
-   * {@inheritdoc}
-   */
-  public function providerSource() {
-    $tests = [];
-
-    // The source data.
-    $tests[0]['database']['boxes'] = [
-      [
-        'bid' => 1,
-        'body' => 'box 1 body',
-        'info' => 'box 1 info',
-        'format' => '2',
-      ],
-      [
-        'bid' => 2,
-        'body' => 'box 2 body',
-        'info' => 'box 2 info',
-        'format' => '2',
-      ],
-    ];
-
-    $tests[0]['database']['i18n_strings'] = [
-      [
-        'lid' => 1,
-        'objectid' => 1,
-        'type' => 'block',
-        'property' => 'title',
-        'objectindex' => 0,
-        'format' => 0,
-      ],
-      [
-        'lid' => 2,
-        'objectid' => 1,
-        'type' => 'block',
-        'property' => 'body',
-        'objectindex' => 0,
-        'format' => 0,
-      ],
-      [
-        'lid' => 3,
-        'objectid' => 2,
-        'type' => 'block',
-        'property' => 'body',
-        'objectindex' => 0,
-        'format' => 2,
-      ],
-    ];
-
-    $tests[0]['database']['locales_target'] = [
-      [
-        'lid' => 1,
-        'language' => 'fr',
-        'translation' => 'fr - info translation',
-        'plid' => 0,
-        'plural' => 0,
-        'i18n_status' => 0,
-      ],
-      [
-        'lid' => 2,
-        'language' => 'fr',
-        'translation' => 'fr - body translation',
-        'plid' => 0,
-        'plural' => 0,
-        'i18n_status' => 0,
-      ],
-      [
-        'lid' => 2,
-        'language' => 'zu',
-        'translation' => 'zu - body translation',
-        'plid' => 0,
-        'plural' => 0,
-        'i18n_status' => 0,
-      ],
-    ];
-
-    // The expected results.
-    $tests[0]['expected_results'] = [
-      [
-        'lid' => '2',
-        'type' => 'block',
-        'property' => 'body',
-        'objectid' => '1',
-        'lt_lid' => '2',
-        'language' => 'fr',
-        'translation' => 'fr - body translation',
-        'bid' => '1',
-        'body' => 'fr - body translation',
-        'info' => 'fr - info translation',
-        'format' => '2',
-      ],
-      [
-        'lid' => '2',
-        'type' => 'block',
-        'property' => 'body',
-        'objectid' => '1',
-        'lt_lid' => '2',
-        'language' => 'zu',
-        'translation' => 'zu - body translation',
-        'bid' => '1',
-        'body' => 'zu - body translation',
-        'info' => 'box 1 info',
-        'format' => '2',
-      ],
-      [
-        'lid' => '3',
-        'type' => 'block',
-        'property' => 'body',
-        'objectid' => '2',
-        'lt_lid' => NULL,
-        'language' => NULL,
-        'translation' => NULL,
-        'bid' => '2',
-        'body' => NULL,
-        'info' => 'box 2 info',
-        'format' => '2',
-      ],
-    ];
-
-    return $tests;
-  }
-
-}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/migration_templates/d6_block_translation.yml
@@ -0,0 +1,64 @@
+id: d6_block_translation
+label: Blocks translation
+migration_tags:
+  - Drupal 6
+source:
+  plugin: d6_block_translation
+  constants:
+    dest_label: 'settings/label'
+process:
+  langcode: language
+  property: constants/dest_label
+  translation: title
+  id:
+    plugin: migration
+    migration: d6_block
+    source:
+      - module
+      - delta
+  plugin:
+    -
+      plugin: static_map
+      bypass: true
+      source:
+        - module
+        - delta
+      map:
+        book:
+          0: book_navigation
+        comment:
+          0: views_block:comments_recent-block_1
+        forum:
+          0: forum_active_block
+          1: forum_new_block
+        locale:
+          0: language_block
+        node:
+          0: node_syndicate_block
+        search:
+          0: search_form_block
+        statistics:
+          0: statistics_popular_block
+        system:
+          0: system_powered_by_block
+        user:
+          0: user_login_block
+          1: system_menu_block:tools
+          2: views_block:who_s_new-block_1
+          3: views_block:who_s_online-who_s_online_block
+    -
+      plugin: block_plugin_id
+    -
+      plugin: skip_on_empty
+      method: row
+  theme:
+    plugin: block_theme
+    source:
+      - theme
+      - default_theme
+      - admin_theme
+destination:
+  plugin: entity:block
+migration_dependencies:
+  required:
+    - d6_block
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/migration_templates/d6_custom_block_translation.yml
@@ -0,0 +1,27 @@
+id: d6_custom_block_translation
+label: Custom blocks
+migration_tags:
+  - Drupal 6
+source:
+  plugin: d6_box_translation
+  constants:
+    type: basic
+process:
+  id: bid
+  langcode: language
+  type: 'constants/type'
+  info: info
+  'body/format':
+    plugin: migration
+    migration: d6_filter_format
+    source: format
+  'body/value': body
+destination:
+  plugin: entity:block_content
+  no_stub: true
+  translations: true
+migration_dependencies:
+  required:
+    - d6_filter_format
+    - block_content_body_field
+    - d6_custom_block
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/src/Plugin/migrate/source/d6/BlockTranslation.php
@@ -0,0 +1,104 @@
+<?php
+
+namespace Drupal\content_translation\Plugin\migrate\source\d6;
+
+use Drupal\migrate\Row;
+use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;
+
+/**
+ * Gets i18n block data from source database.
+ *
+ * @MigrateSource(
+ *   id = "d6_block_translation",
+ *   source_provider = "block"
+ * )
+ */
+class BlockTranslation extends DrupalSqlBase {
+
+  /**
+   * The default theme name.
+   *
+   * @var string
+   */
+  protected $defaultTheme;
+
+  /**
+   * The admin theme name.
+   *
+   * @var string
+   */
+  protected $adminTheme;
+
+  /**
+   * Table containing block configuration.
+   *
+   * @var string
+   */
+  protected $blockTable;
+
+  /**
+   * {@inheritdoc}
+   */
+  public function query() {
+    if ($this->getModuleSchemaVersion('system') >= 7000) {
+      $this->blockTable = 'block';
+    }
+    else {
+      $this->blockTable = 'blocks';
+    }
+
+    $query = $this->select('i18n_blocks', 'i18n')
+      ->fields('i18n', ['ibid', 'module', 'delta', 'type', 'language'])
+      ->fields('b', ['bid', 'module', 'delta', 'theme', 'title']);
+    $query->addField('b', 'module', 'block_module');
+    $query->addField('b', 'delta', 'block_delta');
+    $query->leftJoin($this->blockTable, 'b', ('b.module = i18n.module AND b.delta = i18n.delta'));
+    return $query;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function initializeIterator() {
+    $this->defaultTheme = $this->variableGet('theme_default', 'Garland');
+    $this->adminTheme = $this->variableGet('admin_theme', NULL);
+    return parent::initializeIterator();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function fields() {
+    return [
+      'bid' => $this->t('The block numeric identifier.'),
+      'module' => $this->t('The module providing the block.'),
+      'delta' => $this->t("The block's delta."),
+      'title' => $this->t("Title translation for this language.."),
+      'theme' => $this->t('Which theme the block is placed in.'),
+      'language' => $this->t('Language for this field.'),
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getIds() {
+    $ids['module']['type'] = 'string';
+    $ids['module']['alias'] = 'b';
+    $ids['delta']['type'] = 'string';
+    $ids['delta']['alias'] = 'b';
+    $ids['theme']['type'] = 'string';
+    $ids['language']['type'] = 'string';
+    return $ids;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function prepareRow(Row $row) {
+    $row->setSourceProperty('default_theme', $this->defaultTheme);
+    $row->setSourceProperty('admin_theme', $this->adminTheme);
+    return parent::prepareRow($row);
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/src/Plugin/migrate/source/d6/BoxTranslation.php
@@ -0,0 +1,103 @@
+<?php
+
+namespace Drupal\content_translation\Plugin\migrate\source\d6;
+
+use Drupal\migrate_drupal\Plugin\migrate\source\DrupalSqlBase;
+
+/**
+ * Gets Drupal 6 i18n custom block translations from database.
+ *
+ * @MigrateSource(
+ *   id = "d6_box_translation"
+ * )
+ */
+class BoxTranslation extends DrupalSqlBase {
+
+  const INFO = "CASE WHEN property = 'title' THEN translation ELSE info END";
+  const BODY = "CASE WHEN property = 'body' THEN translation ELSE body END";
+
+  /**
+   * {@inheritdoc}
+   */
+  public function count() {
+    return $this->initializeIterator()->count();
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function initializeIterator() {
+    return new \ArrayIterator($this->values());
+  }
+
+  /**
+   * Merge the block body and info translations into a single row.
+   *
+   * @return array
+   *   An array of ...
+   */
+  protected function values() {
+    $values = [];
+    $result = $this->prepareQuery()->execute()->FetchAll();
+    $cnt = count($result);
+    for ($i = 0; $i < $cnt; $i++) {
+      if (isset($result[$i])) {
+        $j = $i + 1;
+        if (isset($result[$j])) {
+          // If the same bid and language, then this is the info.
+          if ($result[$i]['bid'] == $result[$j]['bid'] and
+            $result[$i]['language'] == $result[$j]['language']
+          ) {
+            $result[$i]['info'] = $result[$j]['info'];
+            unset($result[$j]);
+          }
+        }
+        $values[] = $result[$i];
+      }
+    }
+    return $values;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function query() {
+    $query = $this->select('i18n_strings', 'i18n')
+      ->fields('i18n', ['lid', 'type', 'property', 'objectid'])
+      ->fields('lt', ['lid', 'language', 'translation'])
+      ->fields('b', ['bid', 'body', 'info', 'format'])
+      ->orderBy('bid')
+      ->orderBy('language')
+      ->orderBy('property')
+      ->condition('i18n.type', 'block');
+    $query->addExpression(self::INFO, 'info');
+    $query->addExpression(self::BODY, 'body');
+    $query->leftJoin('boxes', 'b', 'b.bid = i18n.objectid');
+    $query->leftJoin('locales_target', 'lt', 'lt.lid = i18n.lid');
+
+    return $query;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function fields() {
+    return [
+      'bid' => $this->t('The block numeric identifier.'),
+      'language' => $this->t('Language for this field.'),
+      'body' => $this->t('The block/box content'),
+      'info' => $this->t('Admin title of the block/box.'),
+      'format' => $this->t('Input format of the custom block/box content.'),
+    ];
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getIds() {
+    $ids['bid']['type'] = 'integer';
+    $ids['language']['type'] = 'string';
+    return $ids;
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/tests/src/Kernel/Migrate/d6/MigrateBlockContentTranslationTest.php
@@ -0,0 +1,54 @@
+<?php
+
+namespace Drupal\Tests\content_translation\Kernel\Migrate\d6;
+
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Tests migration of i18n block translations.
+ *
+ * @group migrate_drupal_6
+ */
+class MigrateBlockContentTranslationTest extends MigrateDrupal6TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'block',
+    'views',
+    'block_content',
+    'content_translation',
+    'language',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installConfig(['block']);
+    $this->installConfig(['block_content']);
+    $this->installEntitySchema('block_content');
+
+    $this->executeMigrations([
+      'd6_filter_format',
+      'block_content_type',
+      'block_content_body_field',
+      'd6_custom_block',
+      'd6_user_role',
+      'd6_block',
+      'd6_block_translation',
+    ]);
+    block_rebuild();
+  }
+
+  /**
+   * Tests the migration of block title translation.
+   */
+  public function testI18nBlock() {
+    $config = \Drupal::service('language_manager')->getLanguageConfigOverride('zu', 'block.block.user_1');
+    $this->assertSame('zu - Test Title 02', $config->get('settings.label'));
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/tests/src/Kernel/Migrate/d6/MigrateCustomBlockContentTranslationTest.php
@@ -0,0 +1,73 @@
+<?php
+
+namespace Drupal\Tests\content_translation\Kernel\Migrate\d6;
+
+use Drupal\block_content\Entity\BlockContent;
+use Drupal\language\Entity\ConfigurableLanguage;
+use Drupal\Tests\migrate_drupal\Kernel\d6\MigrateDrupal6TestBase;
+
+/**
+ * Tests migration of i18n custom block strings.
+ *
+ * @group migrate_drupal_6
+ */
+class MigrateCustomBlockContentTranslationTest extends MigrateDrupal6TestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = [
+    'block',
+    'block_content',
+    'config_translation',
+    'content_translation',
+    'language',
+  ];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->installConfig(['block_content']);
+    $this->installEntitySchema('block_content');
+    ConfigurableLanguage::createFromLangcode('en')->save();
+    ConfigurableLanguage::createFromLangcode('fr')->save();
+    ConfigurableLanguage::createFromLangcode('zu')->save();
+    $this->executeMigrations([
+      'd6_filter_format',
+      'block_content_type',
+      'block_content_body_field',
+      'd6_custom_block',
+      'd6_custom_block_translation',
+    ]);
+  }
+
+  /**
+   * Tests the Drupal 6 i18n custom block strings to Drupal 8 migration.
+   */
+  public function testBlockMigration() {
+    /** @var BlockContent $block */
+    $block = BlockContent::load(1)->getTranslation('fr');
+    $this->assertSame('fr - Static Block', $block->label());
+    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
+    $this->assertSame('fr', $block->language()->getId());
+    $this->assertSame('<h3>fr - My first custom block body</h3>', $block->body->value);
+    $this->assertSame('full_html', $block->body->format);
+
+    $block = BlockContent::load(1)->getTranslation('zu');
+    $this->assertSame('My block 1', $block->label());
+    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
+    $this->assertSame('zu', $block->language()->getId());
+    $this->assertSame('<h3>zu - My first custom block body</h3>', $block->body->value);
+    $this->assertSame('full_html', $block->body->format);
+
+    $block = BlockContent::load(2)->getTranslation('fr');
+    $this->assertSame('Encore un bloc statique', $block->label());
+    $this->assertTrue(REQUEST_TIME <= $block->getChangedTime() && $block->getChangedTime() <= time());
+    $this->assertSame('fr', $block->language()->getId());
+    $this->assertSame('Nom de vocabulaire beaucoup plus long que trente-deux caractères', $block->body->value);
+    $this->assertSame('full_html', $block->body->format);
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/tests/src/Kernel/Plugin/migrate/source/d6/BlockTranslationTest.php
@@ -0,0 +1,100 @@
+<?php
+
+namespace Drupal\Tests\content_translation\Kernel\Plugin\migrate\source\d6;
+
+use Drupal\Tests\migrate\Kernel\MigrateSqlSourceTestBase;
+
+/**
+ * Tests i18n block title source plugin.
+ *
+ * @covers Drupal\content_translation\Plugin\migrate\source\d6\BlockTranslation
+ *
+ * @group content_translation
+ */
+class BlockTranslationTest extends MigrateSqlSourceTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['content_translation', 'migrate_drupal'];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function providerSource() {
+    $tests = [];
+
+    // The source data.
+    $tests[0]['source_data']['blocks'] = [
+      [
+        'bid' => 1,
+        'module' => 'user',
+        'delta' => '1',
+        'theme' => 'garland',
+        'status' => 1,
+        'weight' => 0,
+        'region' => 'left',
+        'visibility' => 0,
+        'pages' => '',
+        'title' => 'fr - Test Title 01',
+        'cache' => -1,
+      ],
+      [
+        'bid' => 2,
+        'module' => 'user',
+        'delta' => '2',
+        'theme' => 'garland',
+        'status' => 1,
+        'weight' => 5,
+        'region' => 'right',
+        'visibility' => 0,
+        'pages' => '<front>',
+        'title' => 'zu - Test Title 02',
+        'cache' => -1,
+      ],
+    ];
+
+    $tests[0]['source_data']['i18n_blocks'] = [
+      [
+        'ibid' => 1,
+        'module' => 'user',
+        'delta' => '1',
+        'type' => 0,
+        'language' => 'fr',
+      ],
+      [
+        'ibid' => 2,
+        'module' => 'user',
+        'delta' => '2',
+        'type' => 0,
+        'language' => 'zu',
+      ],
+    ];
+
+    // The expected results.
+    $tests[0]['expected_results'] = [
+      [
+        'bid' => 1,
+        'module' => 'user',
+        'delta' => '1',
+        'title' => 'fr - Test Title 01',
+        'ibid' => 1,
+        'type' => '0',
+        'language' => 'fr',
+      ],
+      [
+        'bid' => 2,
+        'module' => 'user',
+        'delta' => '2',
+        'theme' => 'garland',
+        'title' => 'zu - Test Title 02',
+        'ibid' => 2,
+        'type' => '0',
+        'language' => 'zu',
+      ],
+    ];
+
+    return $tests;
+  }
+
+}
only in patch2:
unchanged:
--- /dev/null
+++ b/core/modules/content_translation/tests/src/Kernel/Plugin/migrate/source/d6/BoxTranslationTest.php
@@ -0,0 +1,143 @@
+<?php
+
+namespace Drupal\Tests\content_translation\Kernel\Plugin\migrate\source\d6;
+
+use Drupal\Tests\migrate\Kernel\MigrateSqlSourceTestBase;
+
+/**
+ * Tests i18n block title source plugin.
+ *
+ * @covers Drupal\content_translation\Plugin\migrate\source\d6\BoxTranslation
+ *
+ * @group content_translation
+ */
+class BoxTranslationTest extends MigrateSqlSourceTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['content_translation', 'migrate_drupal'];
+
+  /**
+   * {@inheritdoc}
+   */
+  public function providerSource() {
+    $tests = [];
+
+    // The source data.
+    $tests[0]['database']['boxes'] = [
+      [
+        'bid' => 1,
+        'body' => 'box 1 body',
+        'info' => 'box 1 info',
+        'format' => '2',
+      ],
+      [
+        'bid' => 2,
+        'body' => 'box 2 body',
+        'info' => 'box 2 info',
+        'format' => '2',
+      ],
+    ];
+
+    $tests[0]['database']['i18n_strings'] = [
+      [
+        'lid' => 1,
+        'objectid' => 1,
+        'type' => 'block',
+        'property' => 'title',
+        'objectindex' => 0,
+        'format' => 0,
+      ],
+      [
+        'lid' => 2,
+        'objectid' => 1,
+        'type' => 'block',
+        'property' => 'body',
+        'objectindex' => 0,
+        'format' => 0,
+      ],
+      [
+        'lid' => 3,
+        'objectid' => 2,
+        'type' => 'block',
+        'property' => 'body',
+        'objectindex' => 0,
+        'format' => 2,
+      ],
+    ];
+
+    $tests[0]['database']['locales_target'] = [
+      [
+        'lid' => 1,
+        'language' => 'fr',
+        'translation' => 'fr - info translation',
+        'plid' => 0,
+        'plural' => 0,
+        'i18n_status' => 0,
+      ],
+      [
+        'lid' => 2,
+        'language' => 'fr',
+        'translation' => 'fr - body translation',
+        'plid' => 0,
+        'plural' => 0,
+        'i18n_status' => 0,
+      ],
+      [
+        'lid' => 2,
+        'language' => 'zu',
+        'translation' => 'zu - body translation',
+        'plid' => 0,
+        'plural' => 0,
+        'i18n_status' => 0,
+      ],
+    ];
+
+    // The expected results.
+    $tests[0]['expected_results'] = [
+      [
+        'lid' => '2',
+        'type' => 'block',
+        'property' => 'body',
+        'objectid' => '1',
+        'lt_lid' => '2',
+        'language' => 'fr',
+        'translation' => 'fr - body translation',
+        'bid' => '1',
+        'body' => 'fr - body translation',
+        'info' => 'fr - info translation',
+        'format' => '2',
+      ],
+      [
+        'lid' => '2',
+        'type' => 'block',
+        'property' => 'body',
+        'objectid' => '1',
+        'lt_lid' => '2',
+        'language' => 'zu',
+        'translation' => 'zu - body translation',
+        'bid' => '1',
+        'body' => 'zu - body translation',
+        'info' => 'box 1 info',
+        'format' => '2',
+      ],
+      [
+        'lid' => '3',
+        'type' => 'block',
+        'property' => 'body',
+        'objectid' => '2',
+        'lt_lid' => NULL,
+        'language' => NULL,
+        'translation' => NULL,
+        'bid' => '2',
+        'body' => NULL,
+        'info' => 'box 2 info',
+        'format' => '2',
+      ],
+    ];
+
+    return $tests;
+  }
+
+}