diff --git a/core/modules/aggregator/migrations/d6_aggregator_item.yml b/core/modules/aggregator/migrations/d6_aggregator_item.yml
index 24663735d4..6876629846 100644
--- a/core/modules/aggregator/migrations/d6_aggregator_item.yml
+++ b/core/modules/aggregator/migrations/d6_aggregator_item.yml
@@ -9,9 +9,15 @@ source:
 process:
   iid: iid
   fid:
-    plugin: migration_lookup
-    migration: d6_aggregator_feed
-    source: fid
+    -
+      plugin: migration_lookup
+      migration: d6_aggregator_feed
+      source: fid
+      return_associatve: TRUE
+    -
+      plugin: extract
+      index:
+        - fid
   title: title
   link: link
   author: author
diff --git a/core/modules/aggregator/migrations/d7_aggregator_item.yml b/core/modules/aggregator/migrations/d7_aggregator_item.yml
index 230c3a26ef..76b068a922 100644
--- a/core/modules/aggregator/migrations/d7_aggregator_item.yml
+++ b/core/modules/aggregator/migrations/d7_aggregator_item.yml
@@ -9,9 +9,15 @@ source:
 process:
   iid: iid
   fid:
-    plugin: migration_lookup
-    migration: d7_aggregator_feed
-    source: fid
+    -
+      plugin: migration_lookup
+      migration: d7_aggregator_feed
+      source: fid
+      return_associatve: TRUE
+    -
+      plugin: extract
+      index:
+      - fid
   title: title
   link: link
   author: author
diff --git a/core/modules/block/src/Plugin/migrate/process/BlockPluginId.php b/core/modules/block/src/Plugin/migrate/process/BlockPluginId.php
index 08525674e3..64d179c93d 100644
--- a/core/modules/block/src/Plugin/migrate/process/BlockPluginId.php
+++ b/core/modules/block/src/Plugin/migrate/process/BlockPluginId.php
@@ -52,6 +52,7 @@ public static function create(ContainerInterface $container, array $configuratio
         'd6_custom_block',
         'd7_custom_block',
       ],
+      'return_associative' => TRUE,
     ];
     return new static(
       $configuration,
@@ -84,7 +85,7 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
             $block_id = $this->migrationPlugin
               ->transform($delta, $migrate_executable, $row, $destination_property);
             if ($block_id) {
-              return 'block_content:' . $this->blockContentStorage->load($block_id)->uuid();
+              return 'block_content:' . $this->blockContentStorage->load($block_id['id'])->uuid();
             }
           }
           break;
diff --git a/core/modules/block/src/Plugin/migrate/process/BlockVisibility.php b/core/modules/block/src/Plugin/migrate/process/BlockVisibility.php
index 271edd48c3..3e2c71e109 100644
--- a/core/modules/block/src/Plugin/migrate/process/BlockVisibility.php
+++ b/core/modules/block/src/Plugin/migrate/process/BlockVisibility.php
@@ -64,6 +64,7 @@ public static function create(ContainerInterface $container, array $configuratio
         'd6_user_role',
         'd7_user_role',
       ],
+      'return_associative' => TRUE,
     ];
     return new static(
       $configuration,
@@ -94,7 +95,7 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       ];
 
       foreach ($roles as $key => $role_id) {
-        $roles[$key] = $this->migrationPlugin->transform($role_id, $migrate_executable, $row, $destination_property);
+        $roles[$key] = $this->migrationPlugin->transform($role_id, $migrate_executable, $row, $destination_property)['id'];
       }
       $visibility['user_role']['roles'] = array_combine($roles, $roles);
     }
diff --git a/core/modules/block_content/migrations/d6_custom_block.yml b/core/modules/block_content/migrations/d6_custom_block.yml
index 84e2a4942f..508c0e2932 100644
--- a/core/modules/block_content/migrations/d6_custom_block.yml
+++ b/core/modules/block_content/migrations/d6_custom_block.yml
@@ -10,9 +10,15 @@ process:
   id: bid
   info: info
   'body/format':
-    plugin: migration_lookup
-    migration: d6_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d6_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
   'body/value': body
 destination:
   plugin: entity:block_content
diff --git a/core/modules/block_content/migrations/d7_custom_block.yml b/core/modules/block_content/migrations/d7_custom_block.yml
index 16c659f699..7748ab3d02 100644
--- a/core/modules/block_content/migrations/d7_custom_block.yml
+++ b/core/modules/block_content/migrations/d7_custom_block.yml
@@ -10,9 +10,15 @@ process:
   id: bid
   info: info
   'body/format':
-    plugin: migration_lookup
-    migration: d7_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d7_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
   'body/value': body
 destination:
   plugin: entity:block_content
diff --git a/core/modules/book/migrations/d6_book.yml b/core/modules/book/migrations/d6_book.yml
index 128dfb9a01..a8e4a70a15 100644
--- a/core/modules/book/migrations/d6_book.yml
+++ b/core/modules/book/migrations/d6_book.yml
@@ -16,7 +16,12 @@ process:
       source: plid
     -
       plugin: migration_lookup
+      return_associative: TRUE
       migration: d6_book
+    -
+      plugin: extract
+      index:
+        - nid
 destination:
   plugin: book
 migration_dependencies:
diff --git a/core/modules/book/migrations/d7_book.yml b/core/modules/book/migrations/d7_book.yml
index 30d8c72b57..0616a789a1 100644
--- a/core/modules/book/migrations/d7_book.yml
+++ b/core/modules/book/migrations/d7_book.yml
@@ -16,7 +16,12 @@ process:
       source: plid
     -
       plugin: migration_lookup
+      return_associative: TRUE
       migration: d7_book
+    -
+      plugin: extract
+      index:
+        - nid
 destination:
   plugin: book
 migration_dependencies:
diff --git a/core/modules/comment/migrations/d6_comment.yml b/core/modules/comment/migrations/d6_comment.yml
index e6b4e1295f..f01c719149 100644
--- a/core/modules/comment/migrations/d6_comment.yml
+++ b/core/modules/comment/migrations/d6_comment.yml
@@ -14,12 +14,14 @@ process:
   cid: cid
   pid:
     -
-      plugin: skip_on_empty
-      method: process
-      source: pid
-    -
       plugin: migration_lookup
       migration: d6_comment
+      source: pid
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - cid
   entity_id:
     -
       plugin: migration_lookup
@@ -36,9 +38,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d6_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   langcode: language
   field_name: '@comment_type'
   subject: subject
@@ -53,9 +60,15 @@ process:
   thread: thread
   'comment_body/value': comment
   'comment_body/format':
-    plugin: migration_lookup
-    migration: d6_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d6_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
 destination:
   plugin: entity:comment
 migration_dependencies:
diff --git a/core/modules/comment/migrations/d6_comment_entity_display.yml b/core/modules/comment/migrations/d6_comment_entity_display.yml
index 0934078784..c9a039e7a9 100644
--- a/core/modules/comment/migrations/d6_comment_entity_display.yml
+++ b/core/modules/comment/migrations/d6_comment_entity_display.yml
@@ -19,9 +19,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d6_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   view_mode: 'constants/view_mode'
   options: 'constants/options'
   bundle: type
diff --git a/core/modules/comment/migrations/d6_comment_entity_form_display.yml b/core/modules/comment/migrations/d6_comment_entity_form_display.yml
index b893906f37..3c151607cb 100644
--- a/core/modules/comment/migrations/d6_comment_entity_form_display.yml
+++ b/core/modules/comment/migrations/d6_comment_entity_form_display.yml
@@ -18,9 +18,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d6_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   form_mode: 'constants/form_mode'
   options: 'constants/options'
   bundle: type
diff --git a/core/modules/comment/migrations/d6_comment_entity_form_display_subject.yml b/core/modules/comment/migrations/d6_comment_entity_form_display_subject.yml
index b6acaedb39..99ab674523 100644
--- a/core/modules/comment/migrations/d6_comment_entity_form_display_subject.yml
+++ b/core/modules/comment/migrations/d6_comment_entity_form_display_subject.yml
@@ -22,9 +22,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d6_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   hidden:
     plugin: static_map
     source: comment_subject_field
diff --git a/core/modules/comment/migrations/d6_comment_field.yml b/core/modules/comment/migrations/d6_comment_field.yml
index 3d23dd70a2..376ad70b2d 100644
--- a/core/modules/comment/migrations/d6_comment_field.yml
+++ b/core/modules/comment/migrations/d6_comment_field.yml
@@ -15,9 +15,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d6_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   type: 'constants/type'
   'settings/comment_type': '@field_name'
 destination:
diff --git a/core/modules/comment/migrations/d6_comment_field_instance.yml b/core/modules/comment/migrations/d6_comment_field_instance.yml
index 3c9bc1a5f7..83bb1a9cc1 100644
--- a/core/modules/comment/migrations/d6_comment_field_instance.yml
+++ b/core/modules/comment/migrations/d6_comment_field_instance.yml
@@ -18,9 +18,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d6_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   bundle: type
   'default_value/0/status':
     # We're using static_map instead of default_value otherwise if the source
diff --git a/core/modules/comment/migrations/d7_comment.yml b/core/modules/comment/migrations/d7_comment.yml
index 3db0890899..c1ed94edfe 100644
--- a/core/modules/comment/migrations/d7_comment.yml
+++ b/core/modules/comment/migrations/d7_comment.yml
@@ -21,6 +21,12 @@ process:
     -
       plugin: migration_lookup
       migration: d7_comment
+      source: pid
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - cid
   entity_id:
     -
       plugin: migration_lookup
@@ -37,9 +43,14 @@ process:
       plugin: migration_lookup
       source: node_type
       migration: d7_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   langcode: language
   field_name: '@comment_type'
   subject: subject
diff --git a/core/modules/comment/migrations/d7_comment_entity_display.yml b/core/modules/comment/migrations/d7_comment_entity_display.yml
index 4bad6458e6..bf1fbac20c 100644
--- a/core/modules/comment/migrations/d7_comment_entity_display.yml
+++ b/core/modules/comment/migrations/d7_comment_entity_display.yml
@@ -19,9 +19,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d7_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   view_mode: 'constants/view_mode'
   options: 'constants/options'
   bundle: type
diff --git a/core/modules/comment/migrations/d7_comment_entity_form_display.yml b/core/modules/comment/migrations/d7_comment_entity_form_display.yml
index 99eb5313e2..6581a0e6bb 100644
--- a/core/modules/comment/migrations/d7_comment_entity_form_display.yml
+++ b/core/modules/comment/migrations/d7_comment_entity_form_display.yml
@@ -18,9 +18,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d7_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   form_mode: 'constants/form_mode'
   options: 'constants/options'
   bundle: type
diff --git a/core/modules/comment/migrations/d7_comment_entity_form_display_subject.yml b/core/modules/comment/migrations/d7_comment_entity_form_display_subject.yml
index 703c62e951..58099737e9 100644
--- a/core/modules/comment/migrations/d7_comment_entity_form_display_subject.yml
+++ b/core/modules/comment/migrations/d7_comment_entity_form_display_subject.yml
@@ -22,9 +22,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d7_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   hidden:
     plugin: static_map
     source: comment_subject_field
diff --git a/core/modules/comment/migrations/d7_comment_field.yml b/core/modules/comment/migrations/d7_comment_field.yml
index 8dee88c1fc..1ba0346528 100644
--- a/core/modules/comment/migrations/d7_comment_field.yml
+++ b/core/modules/comment/migrations/d7_comment_field.yml
@@ -15,9 +15,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d7_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   type: 'constants/type'
   'settings/comment_type': '@field_name'
 destination:
diff --git a/core/modules/comment/migrations/d7_comment_field_instance.yml b/core/modules/comment/migrations/d7_comment_field_instance.yml
index aa558e53e1..920235c923 100644
--- a/core/modules/comment/migrations/d7_comment_field_instance.yml
+++ b/core/modules/comment/migrations/d7_comment_field_instance.yml
@@ -18,9 +18,14 @@ process:
       plugin: migration_lookup
       source: type
       migration: d7_comment_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   bundle: type
   'default_value/0/status':
     # We're using static_map instead of default_value otherwise if the source
diff --git a/core/modules/config_translation/migrations/d6_user_profile_field_instance_translation.yml b/core/modules/config_translation/migrations/d6_user_profile_field_instance_translation.yml
index b8a88f43f6..c9483fcc21 100644
--- a/core/modules/config_translation/migrations/d6_user_profile_field_instance_translation.yml
+++ b/core/modules/config_translation/migrations/d6_user_profile_field_instance_translation.yml
@@ -18,13 +18,14 @@ process:
       plugin: migration_lookup
       migration: user_profile_field
       source: fid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
       plugin: extract
       index:
-        - 1
+        - field_name
   property:
     plugin: static_map
     source: property
diff --git a/core/modules/contact/migrations/d6_contact_settings.yml b/core/modules/contact/migrations/d6_contact_settings.yml
index a91a9fb1bb..7d2c187830 100644
--- a/core/modules/contact/migrations/d6_contact_settings.yml
+++ b/core/modules/contact/migrations/d6_contact_settings.yml
@@ -12,9 +12,15 @@ process:
   user_default_enabled: contact_default_status
   'flood/limit': contact_hourly_threshold
   default_form:
-    plugin: migration_lookup
-    migration: contact_category
-    source: default_category
+    -
+      plugin: migration_lookup
+      migration: contact_category
+      source: default_category
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - id
 destination:
   plugin: config
   config_name: contact.settings
diff --git a/core/modules/contact/migrations/d7_contact_settings.yml b/core/modules/contact/migrations/d7_contact_settings.yml
index 282064630c..0e61e960f7 100644
--- a/core/modules/contact/migrations/d7_contact_settings.yml
+++ b/core/modules/contact/migrations/d7_contact_settings.yml
@@ -12,9 +12,15 @@ process:
   user_default_enabled: contact_default_status
   'flood/limit': contact_threshold_limit
   default_form:
-    plugin: migration_lookup
-    migration: contact_category
-    source: default_category
+    -
+      plugin: migration_lookup
+      migration: contact_category
+      source: default_category
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+      - id
 destination:
   plugin: config
   config_name: contact.settings
diff --git a/core/modules/content_translation/migrations/d6_block_translation.yml b/core/modules/content_translation/migrations/d6_block_translation.yml
index a27fcfd9e5..ed86b29a9c 100644
--- a/core/modules/content_translation/migrations/d6_block_translation.yml
+++ b/core/modules/content_translation/migrations/d6_block_translation.yml
@@ -19,9 +19,14 @@ process:
       source:
         - module
         - delta
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   plugin:
     -
       plugin: static_map
diff --git a/core/modules/content_translation/migrations/d6_custom_block_translation.yml b/core/modules/content_translation/migrations/d6_custom_block_translation.yml
index a240667b94..7fe330a9f2 100644
--- a/core/modules/content_translation/migrations/d6_custom_block_translation.yml
+++ b/core/modules/content_translation/migrations/d6_custom_block_translation.yml
@@ -8,10 +8,15 @@ source:
   plugin: d6_box_translation
 process:
   id:
-    plugin: migration_lookup
-    migration: d6_custom_block
-    source:
-      - bid
+    -
+      plugin: migration_lookup
+      migration: d6_custom_block
+      source: bid
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - id
   langcode: language
   info:
     -
@@ -34,9 +39,15 @@ process:
       plugin: callback
       callable: current
   'body/format':
-    plugin: migration_lookup
-    migration: d6_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d6_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
 destination:
   plugin: entity:block_content
   no_stub: true
diff --git a/core/modules/content_translation/migrations/d6_menu_links_translation.yml b/core/modules/content_translation/migrations/d6_menu_links_translation.yml
index 34e4290235..4da5026b0e 100644
--- a/core/modules/content_translation/migrations/d6_menu_links_translation.yml
+++ b/core/modules/content_translation/migrations/d6_menu_links_translation.yml
@@ -35,10 +35,15 @@ process:
       # The menu migration is in the system module.
       migration: d6_menu
       source: menu_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
+      plugin: extract
+      index:
+      - id
+    -
       plugin: static_map
       map:
         management: admin
diff --git a/core/modules/content_translation/migrations/d6_node_translation.yml b/core/modules/content_translation/migrations/d6_node_translation.yml
index 38e6870162..649d7550a5 100644
--- a/core/modules/content_translation/migrations/d6_node_translation.yml
+++ b/core/modules/content_translation/migrations/d6_node_translation.yml
@@ -27,9 +27,15 @@ process:
   promote: promote
   sticky: sticky
   'body/format':
-    plugin: migration_lookup
-    migration: d6_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d6_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
   'body/value': body
   'body/summary': teaser
   revision_uid: revision_uid
diff --git a/core/modules/content_translation/migrations/node_translation_menu_links.yml b/core/modules/content_translation/migrations/node_translation_menu_links.yml
index 837a99b47a..b37aa9ca0b 100644
--- a/core/modules/content_translation/migrations/node_translation_menu_links.yml
+++ b/core/modules/content_translation/migrations/node_translation_menu_links.yml
@@ -23,10 +23,15 @@ process:
         - d6_menu
         - d7_menu
       source: menu_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
+      plugin: extract
+      index:
+        - id
+    -
       plugin: static_map
       map:
         management: admin
@@ -65,6 +70,7 @@ process:
         - d6_node_translation
         - d7_node_translation
       no_stub: true
+      return_associative: TRUE
     -
       # Skip row if the new node ID is empty.
       plugin: skip_on_empty
@@ -75,7 +81,7 @@ process:
       # which is at index 0.
       plugin: extract
       index:
-        - 0
+        - nid
   # This will be used in the "link/uri" and "route" processes below.
   link_path:
     plugin: concat
diff --git a/core/modules/content_translation/migrations/statistics_node_translation_counter.yml b/core/modules/content_translation/migrations/statistics_node_translation_counter.yml
index 0c11cd2114..25b3cf234c 100644
--- a/core/modules/content_translation/migrations/statistics_node_translation_counter.yml
+++ b/core/modules/content_translation/migrations/statistics_node_translation_counter.yml
@@ -15,13 +15,14 @@ process:
         - d6_node_translation
         - d7_node_translation
       source: nid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
       plugin: extract
       index:
-        - 0
+        - nid
   totalcount: totalcount
   daycount: daycount
   timestamp: timestamp
diff --git a/core/modules/field/migrations/d6_field_formatter_settings.yml b/core/modules/field/migrations/d6_field_formatter_settings.yml
index 23ea2bd0e0..7d6ea77d08 100644
--- a/core/modules/field/migrations/d6_field_formatter_settings.yml
+++ b/core/modules/field/migrations/d6_field_formatter_settings.yml
@@ -18,37 +18,40 @@ process:
     -
       plugin: migration_lookup
       migration: d6_field
+      return_associative: TRUE
       source:
         - field_name
     -
       plugin: skip_on_empty
       method: row
-    -
-      plugin: extract
-      index:
-        - 1
   entity_type: 'constants/entity_type'
   bundle:
     -
       plugin: migration_lookup
       migration: d6_node_type
       source: type_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   view_mode:
     -
       plugin: migration_lookup
       migration: d6_view_modes
       source:
         - view_mode
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
       plugin: extract
       index:
-        - 1
+        - mode
     -
       plugin: static_map
       bypass: true
diff --git a/core/modules/field/migrations/d6_field_instance.yml b/core/modules/field/migrations/d6_field_instance.yml
index 45941165a3..48679721fd 100644
--- a/core/modules/field/migrations/d6_field_instance.yml
+++ b/core/modules/field/migrations/d6_field_instance.yml
@@ -17,13 +17,10 @@ process:
     -
       plugin: migration_lookup
       migration: d6_field
+      return_associative: TRUE
       source:
         - field_name
     -
-      plugin: extract
-      index:
-        - 1
-    -
       plugin: skip_on_empty
       method: row
   entity_type: 'constants/entity_type'
@@ -33,9 +30,14 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: type_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   label: label
   description: description
   required: required
diff --git a/core/modules/field/migrations/d6_field_instance_widget_settings.yml b/core/modules/field/migrations/d6_field_instance_widget_settings.yml
index 9faac2f36b..7c30fe74aa 100644
--- a/core/modules/field/migrations/d6_field_instance_widget_settings.yml
+++ b/core/modules/field/migrations/d6_field_instance_widget_settings.yml
@@ -19,13 +19,10 @@ process:
     -
       plugin: migration_lookup
       migration: d6_field
+      return_associative: TRUE
       source:
         - field_name
     -
-      plugin: extract
-      index:
-        - 1
-    -
       plugin: skip_on_empty
       method: row
   bundle:
@@ -33,9 +30,14 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: type_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   form_mode: 'constants/form_mode'
   field_name: field_name
   entity_type: 'constants/entity_type'
diff --git a/core/modules/field/migrations/d7_field_formatter_settings.yml b/core/modules/field/migrations/d7_field_formatter_settings.yml
index b4580a2356..385ebbba0d 100644
--- a/core/modules/field/migrations/d7_field_formatter_settings.yml
+++ b/core/modules/field/migrations/d7_field_formatter_settings.yml
@@ -16,14 +16,11 @@ process:
     -
       plugin: migration_lookup
       migration: d7_field
+      return_associative: TRUE
       source:
         - field_name
         - entity_type
     -
-      plugin: extract
-      index:
-        - 0
-    -
       plugin: skip_on_empty
       method: row
   entity_type: entity_type
@@ -43,10 +40,11 @@ process:
       source:
         - entity_type
         - view_mode
+      return_associative: TRUE
     -
       plugin: extract
       index:
-        - 1
+        - mode
     -
       plugin: static_map
       bypass: true
diff --git a/core/modules/field/migrations/d7_field_instance_widget_settings.yml b/core/modules/field/migrations/d7_field_instance_widget_settings.yml
index eaa7831d69..bb17654267 100644
--- a/core/modules/field/migrations/d7_field_instance_widget_settings.yml
+++ b/core/modules/field/migrations/d7_field_instance_widget_settings.yml
@@ -17,14 +17,11 @@ process:
     -
       plugin: migration_lookup
       migration: d7_field
+      return_associative: TRUE
       source:
         - field_name
         - entity_type
     -
-      plugin: extract
-      index:
-        - 0
-    -
       plugin: skip_on_empty
       method: row
   # The bundle needs to be statically mapped in order to support comment types
diff --git a/core/modules/file/migrations/d6_upload.yml b/core/modules/file/migrations/d6_upload.yml
index 1c34e5873c..9a1c32ec46 100644
--- a/core/modules/file/migrations/d6_upload.yml
+++ b/core/modules/file/migrations/d6_upload.yml
@@ -18,9 +18,15 @@ process:
     source: upload
     process:
       target_id:
-        plugin: migration_lookup
-        migration: d6_file
-        source: fid
+        -
+          plugin: migration_lookup
+          migration: d6_file
+          source: fid
+          return_associative: TRUE
+        -
+          plugin: extract
+          index:
+            - fid
       display: list
       description: description
 destination:
diff --git a/core/modules/file/migrations/d6_upload_entity_display.yml b/core/modules/file/migrations/d6_upload_entity_display.yml
index 945dad58ae..ce224bcb88 100644
--- a/core/modules/file/migrations/d6_upload_entity_display.yml
+++ b/core/modules/file/migrations/d6_upload_entity_display.yml
@@ -20,9 +20,14 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: node_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   view_mode: 'constants/view_mode'
   field_name: 'constants/name'
   type: 'constants/type'
diff --git a/core/modules/file/migrations/d6_upload_entity_form_display.yml b/core/modules/file/migrations/d6_upload_entity_form_display.yml
index 8e08f3b03c..2790fcf051 100644
--- a/core/modules/file/migrations/d6_upload_entity_form_display.yml
+++ b/core/modules/file/migrations/d6_upload_entity_form_display.yml
@@ -21,9 +21,14 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: node_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   field_name: 'constants/name'
   form_mode: 'constants/form_mode'
   type: 'constants/type'
diff --git a/core/modules/file/migrations/d6_upload_field_instance.yml b/core/modules/file/migrations/d6_upload_field_instance.yml
index 4a2ba60e47..99b2d4db30 100644
--- a/core/modules/file/migrations/d6_upload_field_instance.yml
+++ b/core/modules/file/migrations/d6_upload_field_instance.yml
@@ -17,9 +17,14 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: node_type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   field_name: 'constants/name'
   settings: 'constants/settings'
   'settings/file_extensions': file_extensions
diff --git a/core/modules/filter/src/Plugin/migrate/process/d6/FilterFormatPermission.php b/core/modules/filter/src/Plugin/migrate/process/d6/FilterFormatPermission.php
index ae8fb9da64..f9bf4c465b 100644
--- a/core/modules/filter/src/Plugin/migrate/process/d6/FilterFormatPermission.php
+++ b/core/modules/filter/src/Plugin/migrate/process/d6/FilterFormatPermission.php
@@ -42,6 +42,7 @@ public function __construct(array $configuration, $plugin_id, $plugin_definition
   public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
     $migration_plugin_configuration = $configuration + [
       'migration' => 'd6_filter_format',
+      'return_associative' => TRUE,
     ];
 
     return new static(
@@ -64,7 +65,7 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       foreach ($formats as $format) {
         $new_id = $this->migrationPlugin->transform($format, $migrate_executable, $row, $destination_property);
         if ($new_id) {
-          $value[] = 'use text format ' . $new_id;
+          $value[] = 'use text format ' . $new_id['format'];
         }
       }
     }
diff --git a/core/modules/forum/migrations/d6_forum_settings.yml b/core/modules/forum/migrations/d6_forum_settings.yml
index 4d4e2d7c2e..dbba54fb7e 100644
--- a/core/modules/forum/migrations/d6_forum_settings.yml
+++ b/core/modules/forum/migrations/d6_forum_settings.yml
@@ -20,9 +20,15 @@ process:
   'topics/page_limit': forum_per_page
   'topics/order': forum_order
   vocabulary:
-    plugin: migration_lookup
-    migration: d6_taxonomy_vocabulary
-    source: forum_nav_vocabulary
+    -
+      plugin: migration_lookup
+      migration: d6_taxonomy_vocabulary
+      source: forum_nav_vocabulary
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - vid
 destination:
   plugin: config
   config_name: forum.settings
diff --git a/core/modules/forum/migrations/d7_forum_settings.yml b/core/modules/forum/migrations/d7_forum_settings.yml
index 8618b4f477..d20b554aec 100644
--- a/core/modules/forum/migrations/d7_forum_settings.yml
+++ b/core/modules/forum/migrations/d7_forum_settings.yml
@@ -20,9 +20,15 @@ process:
   'topics/page_limit': forum_per_page
   'topics/order': forum_order
   vocabulary:
-    plugin: migration_lookup
-    migration: d7_taxonomy_vocabulary
-    source: forum_nav_vocabulary
+    -
+      plugin: migration_lookup
+      migration: d7_taxonomy_vocabulary
+      source: forum_nav_vocabulary
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - vid
 destination:
   plugin: config
   config_name: forum.settings
diff --git a/core/modules/menu_link_content/migrations/d6_menu_links.yml b/core/modules/menu_link_content/migrations/d6_menu_links.yml
index 404ed186b1..60736d78b3 100644
--- a/core/modules/menu_link_content/migrations/d6_menu_links.yml
+++ b/core/modules/menu_link_content/migrations/d6_menu_links.yml
@@ -16,10 +16,15 @@ process:
       # The menu migration is in the system module.
       migration: d6_menu
       source: menu_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
+      plugin: extract
+      index:
+        - id
+    -
       plugin: static_map
       map:
         management: admin
diff --git a/core/modules/menu_link_content/migrations/d7_menu_links.yml b/core/modules/menu_link_content/migrations/d7_menu_links.yml
index 8f90bc3e49..b2dd641905 100644
--- a/core/modules/menu_link_content/migrations/d7_menu_links.yml
+++ b/core/modules/menu_link_content/migrations/d7_menu_links.yml
@@ -18,9 +18,14 @@ process:
       plugin: migration_lookup
       migration: d7_menu
       source: menu_name
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - id
   'link/uri':
     plugin: link_uri
     source:
diff --git a/core/modules/migrate/src/Plugin/migrate/process/MenuLinkParent.php b/core/modules/migrate/src/Plugin/migrate/process/MenuLinkParent.php
index 2d33e3abe3..62b537d349 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/MenuLinkParent.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/MenuLinkParent.php
@@ -52,7 +52,10 @@ public function __construct(array $configuration, $plugin_id, $plugin_definition
    * {@inheritdoc}
    */
   public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition, MigrationInterface $migration = NULL) {
-    $migration_configuration['migration'][] = $migration->id();
+    $migration_configuration = [
+      'migration' => $migration->id(),
+      'return_associative' => TRUE,
+    ];
     return new static(
       $configuration,
       $plugin_id,
@@ -78,7 +81,7 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       $already_migrated_id = $this
         ->migrationPlugin
         ->transform($parent_id, $migrate_executable, $row, $destination_property);
-      if ($already_migrated_id && ($link = $this->menuLinkStorage->load($already_migrated_id))) {
+      if ($already_migrated_id && ($link = $this->menuLinkStorage->load($already_migrated_id['id']))) {
         return $link->getPluginId();
       }
     }
diff --git a/core/modules/migrate/src/Plugin/migrate/process/MigrationLookup.php b/core/modules/migrate/src/Plugin/migrate/process/MigrationLookup.php
index 57ba7deeea..cf179bbe68 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/MigrationLookup.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/MigrationLookup.php
@@ -3,6 +3,7 @@
 namespace Drupal\migrate\Plugin\migrate\process;
 
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
+use Drupal\migrate\MigrateException;
 use Drupal\migrate\MigrateSkipProcessException;
 use Drupal\migrate\Plugin\MigrationPluginManagerInterface;
 use Drupal\migrate\Plugin\MigrateIdMapInterface;
@@ -30,6 +31,14 @@
  *   any stub entities.
  * - no_stub: (optional) Prevents the creation of a stub entity when no
  *   relationship is found in the migration map.
+ * - return_associative: (bool) Forces the plugin to return destination ids in
+ *   an associative array, keyed as defined by the destination plugin.
+ *   Prior to 8.6 the default behavior was to return a scaler if the destination
+ *   plugin only had one id, and an indexed array if the lookup succeeded
+ *   and there were multiple destination ids.  Beginning in 8.7, this behavior
+ *   is depricated and it is required to specify return_associative:true if
+ *   your lookup returns one of the above scenarios.  Beginning in Drupal 9.0
+ *   this will be the default behavior.
  *
  * Examples:
  *
@@ -158,6 +167,11 @@ public static function create(ContainerInterface $container, array $configuratio
    * @throws \Drupal\migrate\MigrateSkipProcessException
    */
   public function transform($value, MigrateExecutableInterface $migrate_executable, Row $row, $destination_property) {
+    if (isset($this->configuration['return_associative']) && $this->configuration['return_associative'] !== TRUE) {
+      throw new MigrateException("Using a value for return_associative other than true is not supported");
+    }
+
+    $return_associative = isset($this->configuration['return_associative']);
     $lookup_migrations_ids = $this->configuration['migration'];
     if (!is_array($lookup_migrations_ids)) {
       $lookup_migrations_ids = [$lookup_migrations_ids];
@@ -183,6 +197,13 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
       $source_id_values[$lookup_migration_id] = $value;
       // Break out of the loop as soon as a destination ID is found.
       if ($destination_ids = $lookup_migration->getIdMap()->lookupDestinationId($source_id_values[$lookup_migration_id])) {
+        if ($return_associative) {
+          $destination_keys = array_keys($lookup_migration->getDestinationPlugin()->getIds());
+          $destination_ids = array_combine($destination_keys, $destination_ids);
+        }
+        else {
+          $this->triggerNonAssociativeReturnDeprecationError();
+        }
         break;
       }
     }
@@ -230,10 +251,14 @@ public function transform($value, MigrateExecutableInterface $migrate_executable
 
       if ($destination_ids) {
         $id_map->saveIdMapping($stub_row, $destination_ids, MigrateIdMapInterface::STATUS_NEEDS_UPDATE);
+        if ($return_associative) {
+          $destination_ids = array_combine(array_keys($destination_plugin->getIds()), array_values($destination_ids));
+        }
       }
     }
     if ($destination_ids) {
-      if (count($destination_ids) == 1) {
+      if (count($destination_ids) == 1  && !$return_associative) {
+        $this->triggerNonAssociativeReturnDeprecationError();
         return reset($destination_ids);
       }
       else {
@@ -290,4 +315,19 @@ protected function createStubRow(array $values, array $source_ids) {
     return new Row($values, $source_ids, TRUE);
   }
 
+  /**
+   * Triggers an error when using deprecated configuration.
+   *
+   * @deprecated It is deprecated in Drupal 8.7.0 to return a scalar or indexed
+   * array from the migrate_lookup plugin. use return_associative: true and
+   * process the resulting associative array instead. This will be the default
+   * behavior beginning in Drupal 9.0
+   *
+   * @see https://www.drupal.org/node/2996553
+   */
+  protected function triggerNonAssociativeReturnDeprecationError() {
+    @trigger_error('It is deprecated in Drupal 8.7.0 to return a scalar or indexed array from the migrate_lookup plugin. use return_associative: true and process the resulting associative array instead. This will be the default behavior beginning in Drupal 9.0. See https://www.drupal.org/node/2996553', E_USER_DEPRECATED);
+
+  }
+
 }
diff --git a/core/modules/migrate/tests/modules/migrate_external_translated_test/migrations/external_translated_test_node_translation.yml b/core/modules/migrate/tests/modules/migrate_external_translated_test/migrations/external_translated_test_node_translation.yml
index 0363aa2021..aee0ee9f54 100644
--- a/core/modules/migrate/tests/modules/migrate_external_translated_test/migrations/external_translated_test_node_translation.yml
+++ b/core/modules/migrate/tests/modules/migrate_external_translated_test/migrations/external_translated_test_node_translation.yml
@@ -7,9 +7,15 @@ source:
     type: external_test
 process:
   nid:
-    plugin: migration_lookup
-    source: name
-    migration: external_translated_test_node
+    -
+      plugin: migration_lookup
+      source: name
+      migration: external_translated_test_node
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - nid
   type: constants/type
   title: title
   langcode:
diff --git a/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php b/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php
index 65073b72b6..869ba48ebb 100644
--- a/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php
+++ b/core/modules/migrate/tests/src/Unit/process/MigrationLookupTest.php
@@ -3,6 +3,7 @@
 namespace Drupal\Tests\migrate\Unit\process;
 
 use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\migrate\MigrateException;
 use Drupal\migrate\MigrateSkipProcessException;
 use Drupal\migrate\Plugin\MigrationInterface;
 use Drupal\migrate\Plugin\migrate\process\MigrationLookup;
@@ -11,6 +12,7 @@
 use Drupal\migrate\Plugin\MigrateSourceInterface;
 use Drupal\migrate\Plugin\MigrationPluginManagerInterface;
 use Drupal\migrate\Row;
+use Drupal\Tests\Traits\ExpectDeprecationTrait;
 use Prophecy\Argument;
 
 /**
@@ -18,6 +20,7 @@
  * @group migrate
  */
 class MigrationLookupTest extends MigrateProcessTestCase {
+  use ExpectDeprecationTrait;
 
   /**
    * @covers ::transform
@@ -50,6 +53,7 @@ public function testTransformWithStubSkipping() {
 
   /**
    * @covers ::transform
+   * @group legacy
    */
   public function testTransformWithStubbing() {
     $migration_plugin = $this->prophesize(MigrationInterface::class);
@@ -171,7 +175,7 @@ public function noSkipValidDataProvider() {
   /**
    * Tests a successful lookup.
    *
-   * @dataProvider successfulLookupDataProvider
+   * This tests lookups in the non-associative deprecated format.
    *
    * @param array $source_id_values
    *   The source id(s) of the migration map.
@@ -181,8 +185,11 @@ public function noSkipValidDataProvider() {
    *   The source value(s) for the migration process plugin.
    * @param string|array $expected_value
    *   The expected value(s) of the migration process plugin.
+   *
+   * @dataProvider successfulLookupDataProvider
+   * @group legacy
    */
-  public function testSuccessfulLookup($source_id_values, $destination_id_values, $source_value, $expected_value) {
+  public function testSuccessfulLookup(array $source_id_values, array $destination_id_values, $source_value, $expected_value) {
     $migration_plugin = $this->prophesize(MigrationInterface::class);
     $migration_plugin_manager = $this->prophesize(MigrationPluginManagerInterface::class);
 
@@ -205,12 +212,18 @@ public function testSuccessfulLookup($source_id_values, $destination_id_values,
 
     $migration = new MigrationLookup($configuration, 'migration_lookup', [], $migration_plugin->reveal(), $migration_plugin_manager->reveal());
     $this->assertSame($expected_value, $migration->transform($source_value, $this->migrateExecutable, $this->row, 'foo'));
+
+    $this->expectDeprecation('It is deprecated in Drupal 8.7.0 to return a scalar or indexed array from the migrate_lookup plugin. use return_associative: true and process the resulting associative array instead. This will be the default behavior beginning in Drupal 9.0. See https://www.drupal.org/node/2996553');
+    $actual_value = $migration->transform($source_value, $this->migrateExecutable, $this->row, 'foo');
+
+    $this->assertSame($expected_value, $actual_value);
   }
 
   /**
    * Provides data for the successful lookup test.
    *
    * @return array
+   *   The array of test data.
    */
   public function successfulLookupDataProvider() {
     return [
@@ -273,6 +286,108 @@ public function successfulLookupDataProvider() {
   }
 
   /**
+   * Test lookup return as associative array.
+   *
+   * @param array $source_id_values
+   *   The source id(s) of the migration map.
+   * @param array $destination_id_values
+   *   The destination id(s) of the migration map.
+   * @param string|array $source_value
+   *   The source value(s) for the migration process plugin.
+   * @param string|array $expected_value
+   *   The expected value(s) of the migration process plugin.
+   *
+   * @dataProvider successfulLookupAssocDataProvider
+   */
+  public function testSuccessfulLookupAssoc(array $source_id_values, array $destination_id_values, $source_value, $expected_value) {
+    $migration_plugin = $this->prophesize(MigrationInterface::class);
+    $migration_plugin_manager = $this->prophesize(MigrationPluginManagerInterface::class);
+    $process_plugin_manager = $this->prophesize(MigratePluginManager::class);
+    $destination_plugin = $this->prophesize(MigrateDestinationInterface::class);
+    $destination_keys = ['id1' => [], 'id2' => []];
+
+    $destination_plugin->getIds()->willReturn(array_slice($destination_keys, 0, count($destination_id_values)));
+
+    $configuration = [
+      'migration' => 'foobaz',
+      'return_associative' => TRUE,
+    ];
+    $migration_plugin->id()->willReturn(uniqid());
+
+    $id_map = $this->prophesize(MigrateIdMapInterface::class);
+    $id_map->lookupDestinationId($source_id_values)->willReturn($destination_id_values);
+    $migration_plugin->getIdMap()->willReturn($id_map->reveal());
+    $migration_plugin->getDestinationPlugin()->willReturn($destination_plugin->reveal());
+
+    $migration_plugin_manager->createInstances(['foobaz'])
+      ->willReturn(['foobaz' => $migration_plugin->reveal()]);
+
+    $migrationStorage = $this->prophesize(EntityStorageInterface::class);
+    $migrationStorage
+      ->loadMultiple(['foobaz'])
+      ->willReturn([$migration_plugin->reveal()]);
+
+    $migration = new MigrationLookup($configuration, 'migration_lookup', [], $migration_plugin->reveal(), $migration_plugin_manager->reveal(), $process_plugin_manager->reveal());
+    $actual_value = $migration->transform($source_value, $this->migrateExecutable, $this->row, 'foo');
+    $this->assertSame($expected_value, $actual_value);
+  }
+
+  /**
+   * Provides data for the successful lookup test.
+   *
+   * @return array
+   *   The data.
+   */
+  public function successfulLookupAssocDataProvider() {
+    return [
+      // Test data for scalar to scalar.
+      [
+        // Source ID of the migration map.
+        [1],
+        // Destination ID of the migration map.
+        [3],
+        // Input value for the migration plugin.
+        1,
+        // Expected output value of the migration plugin.
+        ['id1' => 3],
+      ],
+      // Test data for scalar to array.
+      [
+        // Source ID of the migration map.
+        [1],
+        // Destination IDs of the migration map.
+        [3, 'foo'],
+        // Input value for the migration plugin.
+        1,
+        // Expected output values of the migration plugin.
+        ['id1' => 3, 'id2' => 'foo'],
+      ],
+      // Test data for array to scalar.
+      [
+        // Source IDs of the migration map.
+        [1, 3],
+        // Destination ID of the migration map.
+        ['foo'],
+        // Input values for the migration plugin.
+        [1, 3],
+        // Expected output value of the migration plugin.
+        ['id1' => 'foo'],
+      ],
+      // Test data for array to array.
+      [
+        // Source IDs of the migration map.
+        [1, 3],
+        // Destination IDs of the migration map.
+        [3, 'foo'],
+        // Input values for the migration plugin.
+        [1, 3],
+        // Expected output values of the migration plugin.
+        ['id1' => 3, 'id2' => 'foo'],
+      ],
+    ];
+  }
+
+  /**
    * Tests that a message is successfully created if import fails.
    */
   public function testImportException() {
@@ -312,6 +427,8 @@ public function testImportException() {
 
   /**
    * Tests processing multiple source IDs.
+   *
+   * @group legacy
    */
   public function testMultipleSourceIds() {
     $migration_plugin = $this->prophesize(MigrationInterface::class);
@@ -360,4 +477,22 @@ public function testMultipleSourceIds() {
     $this->assertEquals(2, $result);
   }
 
+  /**
+   * Tests that an exception is thrown if return_associative is set to false.
+   */
+  public function testUnsupportedConfig() {
+    $migration_plugin = $this->prophesize(MigrationInterface::class);
+    $migration_plugin_manager = $this->prophesize(MigrationPluginManagerInterface::class);
+    $process_plugin_manager = $this->prophesize(MigratePluginManager::class);
+    $configuration = [
+      'migration' => 'foobaz',
+      'return_associative' => FALSE,
+    ];
+
+    $migration_plugin = new MigrationLookup($configuration, 'migration_lookup', [], $migration_plugin->reveal(), $migration_plugin_manager->reveal(), $process_plugin_manager->reveal());
+
+    $this->expectException(MigrateException::class);
+    $migration_plugin->transform(1, $this->migrateExecutable, $this->row, 'foo');
+  }
+
 }
diff --git a/core/modules/migrate_drupal/src/Plugin/migrate/field/UserReference.php b/core/modules/migrate_drupal/src/Plugin/migrate/field/UserReference.php
index 4a60f450de..f9f93d6224 100644
--- a/core/modules/migrate_drupal/src/Plugin/migrate/field/UserReference.php
+++ b/core/modules/migrate_drupal/src/Plugin/migrate/field/UserReference.php
@@ -26,9 +26,16 @@ public function defineValueProcessPipeline(MigrationInterface $migration, $field
       'source' => $field_name,
       'process' => [
         'target_id' => [
-          'plugin' => 'migration_lookup',
-          'migration' => 'd6_user',
-          'source' => 'uid',
+          [
+            'plugin' => 'migration_lookup',
+            'migration' => 'd6_user',
+            'source' => 'uid',
+            'return_associative' => TRUE,
+          ],
+          [
+            'plugin' => 'extract',
+            'index' => ['uid']
+          ],
         ],
       ],
     ];
diff --git a/core/modules/node/migrations/d6_node.yml b/core/modules/node/migrations/d6_node.yml
index 524448bc38..5d165a5745 100644
--- a/core/modules/node/migrations/d6_node.yml
+++ b/core/modules/node/migrations/d6_node.yml
@@ -27,9 +27,15 @@ process:
   promote: promote
   sticky: sticky
   'body/format':
-    plugin: migration_lookup
-    migration: d6_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d6_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
   'body/value': body
   'body/summary': teaser
   revision_uid: revision_uid
diff --git a/core/modules/node/migrations/d6_node_revision.yml b/core/modules/node/migrations/d6_node_revision.yml
index 732c9abe27..498797ce1f 100644
--- a/core/modules/node/migrations/d6_node_revision.yml
+++ b/core/modules/node/migrations/d6_node_revision.yml
@@ -24,9 +24,15 @@ process:
   promote: promote
   sticky: sticky
   'body/format':
-    plugin: migration_lookup
-    migration: d6_filter_format
-    source: format
+    -
+      plugin: migration_lookup
+      migration: d6_filter_format
+      source: format
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - format
   'body/value': body
   'body/summary': teaser
   revision_uid: revision_uid
diff --git a/core/modules/path/migrations/d6_url_alias.yml b/core/modules/path/migrations/d6_url_alias.yml
index 6263ae2a02..7ebf088b2c 100644
--- a/core/modules/path/migrations/d6_url_alias.yml
+++ b/core/modules/path/migrations/d6_url_alias.yml
@@ -35,5 +35,6 @@ process:
     -
       plugin: migration_lookup
       migration: d6_node_translation
+      return_associative: TRUE
 destination:
   plugin: url_alias
diff --git a/core/modules/path/migrations/d7_url_alias.yml b/core/modules/path/migrations/d7_url_alias.yml
index a4172dcf26..c601281b6d 100644
--- a/core/modules/path/migrations/d7_url_alias.yml
+++ b/core/modules/path/migrations/d7_url_alias.yml
@@ -33,5 +33,6 @@ process:
     -
       plugin: migration_lookup
       migration: d7_node_translation
+      return_associative: TRUE
 destination:
   plugin: url_alias
diff --git a/core/modules/path/src/Plugin/migrate/destination/UrlAlias.php b/core/modules/path/src/Plugin/migrate/destination/UrlAlias.php
index a845fb3908..53ebd39c17 100644
--- a/core/modules/path/src/Plugin/migrate/destination/UrlAlias.php
+++ b/core/modules/path/src/Plugin/migrate/destination/UrlAlias.php
@@ -69,8 +69,8 @@ public function import(Row $row, array $old_destination_id_values = []) {
 
       // Replace the alias source with the translation source path.
       $node_translation = $row->getDestinationProperty('node_translation');
-      $source = '/node/' . $node_translation[0];
-      $langcode = $node_translation[1];
+      $source = '/node/' . $node_translation['nid'];
+      $langcode = $node_translation['langcode'];
     }
 
     $path = $this->aliasStorage->save($source, $alias, $langcode, $pid);
diff --git a/core/modules/shortcut/migrations/d7_shortcut.yml b/core/modules/shortcut/migrations/d7_shortcut.yml
index f4265a8750..8ce5030e63 100644
--- a/core/modules/shortcut/migrations/d7_shortcut.yml
+++ b/core/modules/shortcut/migrations/d7_shortcut.yml
@@ -9,9 +9,15 @@ source:
     uri_scheme: 'internal:/'
 process:
   shortcut_set:
-     plugin: migration_lookup
-     migration: d7_shortcut_set
-     source: menu_name
+    -
+      plugin: migration_lookup
+      migration: d7_shortcut_set
+      source: menu_name
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - id
   title: link_title
   weight: weight
   link:
diff --git a/core/modules/shortcut/migrations/d7_shortcut_set_users.yml b/core/modules/shortcut/migrations/d7_shortcut_set_users.yml
index 9797c0a26f..834b3e364e 100644
--- a/core/modules/shortcut/migrations/d7_shortcut_set_users.yml
+++ b/core/modules/shortcut/migrations/d7_shortcut_set_users.yml
@@ -14,6 +14,10 @@ process:
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - uid
   set_name:
     plugin: migration_lookup
     migration: d7_shortcut_set
diff --git a/core/modules/statistics/migrations/statistics_node_counter.yml b/core/modules/statistics/migrations/statistics_node_counter.yml
index 748a4a83c0..5e5e2251a1 100644
--- a/core/modules/statistics/migrations/statistics_node_counter.yml
+++ b/core/modules/statistics/migrations/statistics_node_counter.yml
@@ -12,9 +12,14 @@ process:
       plugin: migration_lookup
       migration: [d6_node, d7_node]
       source: nid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - nid
   totalcount: totalcount
   daycount: daycount
   timestamp: timestamp
diff --git a/core/modules/taxonomy/migrations/d6_taxonomy_term.yml b/core/modules/taxonomy/migrations/d6_taxonomy_term.yml
index 497d7e7e8d..1ce2c7cf5b 100644
--- a/core/modules/taxonomy/migrations/d6_taxonomy_term.yml
+++ b/core/modules/taxonomy/migrations/d6_taxonomy_term.yml
@@ -11,9 +11,15 @@ process:
   # the tid field to allow incremental migrations.
   tid: tid
   vid:
-    plugin: migration_lookup
-    migration: d6_taxonomy_vocabulary
-    source: vid
+    -
+      plugin: migration_lookup
+      migration: d6_taxonomy_vocabulary
+      source: vid
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - vid
   name: name
   description: description
   weight: weight
@@ -26,6 +32,11 @@ process:
     -
       plugin: migration_lookup
       migration: d6_taxonomy_term
+      return_associative: true
+    -
+      plugin: extract
+      index:
+        - tid
   parent:
     plugin: default_value
     default_value: 0
diff --git a/core/modules/taxonomy/migrations/d6_term_node.yml b/core/modules/taxonomy/migrations/d6_term_node.yml
index fdb8cc9a41..7a7642bc43 100644
--- a/core/modules/taxonomy/migrations/d6_term_node.yml
+++ b/core/modules/taxonomy/migrations/d6_term_node.yml
@@ -12,9 +12,14 @@ process:
       plugin: migration_lookup
       migration: d6_node
       source: nid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - nid
   type: type
   # The actual field name is dynamic and will be added by the builder.
 destination:
diff --git a/core/modules/taxonomy/migrations/d6_term_node_revision.yml b/core/modules/taxonomy/migrations/d6_term_node_revision.yml
index 9487984f94..3de5d85137 100644
--- a/core/modules/taxonomy/migrations/d6_term_node_revision.yml
+++ b/core/modules/taxonomy/migrations/d6_term_node_revision.yml
@@ -13,9 +13,14 @@ process:
       plugin: migration_lookup
       migration: d6_node_revision
       source: vid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - vid
   type: type
   # The actual field name is dynamic and will be added by the builder.
 destination:
diff --git a/core/modules/taxonomy/migrations/d6_vocabulary_entity_display.yml b/core/modules/taxonomy/migrations/d6_vocabulary_entity_display.yml
index 760b6dde39..c1c8740ae3 100644
--- a/core/modules/taxonomy/migrations/d6_vocabulary_entity_display.yml
+++ b/core/modules/taxonomy/migrations/d6_vocabulary_entity_display.yml
@@ -22,18 +22,25 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   # This value is only used in the 'field_name' process pipeline below.
   raw_field_name:
     -
       plugin: migration_lookup
       migration: d6_taxonomy_vocabulary
       source: vid
+      return_associative: TRUE
     -
-      plugin: skip_on_empty
-      method: row
+      plugin: extract
+      index:
+      - vid
   field_name:
     # Prepend field_ to avoid conflicts with base fields, and make sure the
     # result is no longer than 32 characters.
diff --git a/core/modules/taxonomy/migrations/d6_vocabulary_entity_form_display.yml b/core/modules/taxonomy/migrations/d6_vocabulary_entity_form_display.yml
index da8cd2704b..5fcf29e17c 100644
--- a/core/modules/taxonomy/migrations/d6_vocabulary_entity_form_display.yml
+++ b/core/modules/taxonomy/migrations/d6_vocabulary_entity_form_display.yml
@@ -26,18 +26,28 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   # This value is only used in the 'field_name' process pipeline below.
   raw_field_name:
     -
       plugin: migration_lookup
       migration: d6_taxonomy_vocabulary
       source: vid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - vid
   field_name:
     # Prepend field_ to avoid conflicts with base fields, and make sure the
     # result is no longer than 32 characters.
diff --git a/core/modules/taxonomy/migrations/d6_vocabulary_field.yml b/core/modules/taxonomy/migrations/d6_vocabulary_field.yml
index 36974e159c..5cdeffc521 100644
--- a/core/modules/taxonomy/migrations/d6_vocabulary_field.yml
+++ b/core/modules/taxonomy/migrations/d6_vocabulary_field.yml
@@ -19,9 +19,14 @@ process:
       plugin: migration_lookup
       migration: d6_taxonomy_vocabulary
       source: vid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - vid
   field_name:
     # Prepend field_ to avoid conflicts with base fields, and make sure the
     # result is no longer than 32 characters.
diff --git a/core/modules/taxonomy/migrations/d6_vocabulary_field_instance.yml b/core/modules/taxonomy/migrations/d6_vocabulary_field_instance.yml
index 2206cfb57a..46714d91c6 100644
--- a/core/modules/taxonomy/migrations/d6_vocabulary_field_instance.yml
+++ b/core/modules/taxonomy/migrations/d6_vocabulary_field_instance.yml
@@ -17,18 +17,28 @@ process:
       plugin: migration_lookup
       migration: d6_node_type
       source: type
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - type
   # This value is only used in the 'field_name' process pipeline below.
   raw_field_name:
     -
       plugin: migration_lookup
       migration: d6_taxonomy_vocabulary
       source: vid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
+    -
+      plugin: extract
+      index:
+        - vid
   field_name:
     # Prepend field_ to avoid conflicts with base fields, and make sure the
     # result is no longer than 32 characters.
diff --git a/core/modules/taxonomy/migrations/d7_taxonomy_term.yml b/core/modules/taxonomy/migrations/d7_taxonomy_term.yml
index 1bae2d6e32..a567a6e376 100644
--- a/core/modules/taxonomy/migrations/d7_taxonomy_term.yml
+++ b/core/modules/taxonomy/migrations/d7_taxonomy_term.yml
@@ -12,9 +12,15 @@ process:
   # the tid field to allow incremental migrations.
   tid: tid
   vid:
-    plugin: migration_lookup
-    migration: d7_taxonomy_vocabulary
-    source: vid
+    -
+      plugin: migration_lookup
+      migration: d7_taxonomy_vocabulary
+      source: vid
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+      - vid
   name: name
   'description/value': description
   'description/format': format
@@ -28,6 +34,11 @@ process:
     -
       plugin: migration_lookup
       migration: d7_taxonomy_term
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - tid
   parent:
     plugin: default_value
     default_value: 0
diff --git a/core/modules/taxonomy/tests/modules/taxonomy_term_stub_test/migrations/taxonomy_term_stub_test.yml b/core/modules/taxonomy/tests/modules/taxonomy_term_stub_test/migrations/taxonomy_term_stub_test.yml
index 4c3cd86710..9d5a3d0b3d 100644
--- a/core/modules/taxonomy/tests/modules/taxonomy_term_stub_test/migrations/taxonomy_term_stub_test.yml
+++ b/core/modules/taxonomy/tests/modules/taxonomy_term_stub_test/migrations/taxonomy_term_stub_test.yml
@@ -19,9 +19,15 @@ process:
   name: name
   weight: weight
   parent:
-    plugin: migration_lookup
-    migration: taxonomy_term_stub_test
-    source: parent
+    -
+      plugin: migration_lookup
+      migration: taxonomy_term_stub_test
+      source: parent
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - tid
 destination:
   plugin: entity:taxonomy_term
 migration_dependencies:
diff --git a/core/modules/text/src/Plugin/migrate/field/d6/TextField.php b/core/modules/text/src/Plugin/migrate/field/d6/TextField.php
index dba6398a06..74c9f243e9 100644
--- a/core/modules/text/src/Plugin/migrate/field/d6/TextField.php
+++ b/core/modules/text/src/Plugin/migrate/field/d6/TextField.php
@@ -86,7 +86,12 @@ public function defineValueProcessPipeline(MigrationInterface $migration, $field
               'd7_filter_format',
             ],
             'source' => 'format',
+            'return_associative' => TRUE,
           ],
+          [
+            'plugin' => 'extract',
+            'index' => ['format']
+          ]
         ],
       ];
     }
diff --git a/core/modules/user/migrations/d6_user.yml b/core/modules/user/migrations/d6_user.yml
index b3d84534d0..d0c172e4d5 100644
--- a/core/modules/user/migrations/d6_user.yml
+++ b/core/modules/user/migrations/d6_user.yml
@@ -34,14 +34,29 @@ process:
     fallback_to_site_default: true
   init: init
   roles:
-    plugin: migration_lookup
-    migration: d6_user_role
-    source: roles
+    -
+      plugin: migration_lookup
+      migration: d6_user_role
+      source: roles
+      return_associative: TRUE
+    -
+      plugin: sub_process
+      process:
+        target_id: id
   user_picture:
-    plugin: migration_lookup
-    migration: d6_user_picture_file
-    source: uid
-    no_stub: true
+    -
+      plugin: migration_lookup
+      migration: d6_user_picture_file
+      source: uid
+      no_stub: true
+      return_associative: TRUE
+    -
+      plugin: skip_on_empty
+      method: process
+    -
+      plugin: extract
+      index:
+        - fid
 destination:
   plugin: entity:user
   md5_passwords: true
diff --git a/core/modules/user/migrations/d7_user.yml b/core/modules/user/migrations/d7_user.yml
index 5adbe05e8a..aeb0378b0e 100644
--- a/core/modules/user/migrations/d7_user.yml
+++ b/core/modules/user/migrations/d7_user.yml
@@ -33,9 +33,15 @@ process:
     fallback_to_site_default: true
   init: init
   roles:
-    plugin: migration_lookup
-    migration: d7_user_role
-    source: roles
+    -
+      plugin: migration_lookup
+      migration: d7_user_role
+      source: roles
+      return_associative: TRUE
+    -
+      plugin: sub_process
+      process:
+        target_id: id
   user_picture:
     -
       plugin: default_value
@@ -44,6 +50,11 @@ process:
     -
       plugin: migration_lookup
       migration: d7_file
+      return_associative: TRUE
+    -
+      plugin: extract
+      index:
+        - fid
 destination:
   plugin: entity:user
 migration_dependencies:
diff --git a/core/modules/user/migrations/user_profile_entity_display.yml b/core/modules/user/migrations/user_profile_entity_display.yml
index eafba00475..500ab9f0f6 100644
--- a/core/modules/user/migrations/user_profile_entity_display.yml
+++ b/core/modules/user/migrations/user_profile_entity_display.yml
@@ -22,13 +22,14 @@ process:
       plugin: migration_lookup
       migration: user_profile_field
       source: fid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
       plugin: extract
       index:
-        - 1
+        - field_name
   type:
     plugin: static_map
     source: type
diff --git a/core/modules/user/migrations/user_profile_entity_form_display.yml b/core/modules/user/migrations/user_profile_entity_form_display.yml
index 7416ac87a6..97161371c7 100644
--- a/core/modules/user/migrations/user_profile_entity_form_display.yml
+++ b/core/modules/user/migrations/user_profile_entity_form_display.yml
@@ -19,13 +19,14 @@ process:
       plugin: migration_lookup
       migration: user_profile_field
       source: fid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
       plugin: extract
       index:
-        - 1
+        - field_name
   form_mode: 'constants/form_mode'
   type:
     plugin: static_map
diff --git a/core/modules/user/migrations/user_profile_field_instance.yml b/core/modules/user/migrations/user_profile_field_instance.yml
index b6c706ceb7..bade6af0ed 100644
--- a/core/modules/user/migrations/user_profile_field_instance.yml
+++ b/core/modules/user/migrations/user_profile_field_instance.yml
@@ -19,13 +19,14 @@ process:
       plugin: migration_lookup
       migration: user_profile_field
       source: fid
+      return_associative: TRUE
     -
       plugin: skip_on_empty
       method: row
     -
       plugin: extract
       index:
-        - 1
+        - field_name
   required: required
 destination:
   plugin: entity:field_config