Update to Drupal 8.2.4. For more information, see https://www.drupal.org/project/drupal/releases/8.2.4

core/modules/language/migration_templates/d6_language_negotiation_settings.yml

@@ -0,0 +1,34 @@
+id: d6_language_negotiation_settings
+label: Language negotiation settings
+migration_tags:
+  - Drupal 6
+source:
+  plugin: variable
+  variables:
+    - language_negotiation
+process:
+  session/parameter:
+    plugin: default_value
+    default_value: 'language'
+  selected_langcode:
+    plugin: default_value
+    default_value: 'site_default'
+  url/source:
+    plugin: static_map
+    source: language_negotiation
+    default_value: path_prefix
+    map:
+      # LANGUAGE_NEGOTIATION_NONE = 0
+      # LANGUAGE_NEGOTIATION_PATH_DEFAULT = 1
+      # LANGUAGE_NEGOTIATION_PATH = 2
+      # LANGUAGE_NEGOTIATION_DOMAIN = 3
+      0: path_prefix
+      1: path_prefix
+      2: path_prefix
+      3: domain
+destination:
+  plugin: config
+  config_name: language.negotiation
+migration_dependencies:
+  required:
+    - language

core/modules/language/migration_templates/d6_language_types.yml

@@ -0,0 +1,52 @@
+id: d6_language_types
+label: Language types
+migration_tags:
+  - Drupal 6
+source:
+  plugin: variable
+  variables:
+    - language_negotiation
+process:
+  all:
+    plugin: default_value
+    default_value:
+      - 'language_interface'
+      - 'language_content'
+      - 'language_url'
+  configurable:
+    plugin: default_value
+    default_value:
+      - 'language_interface'
+  negotiation/language_content/enabled:
+    plugin: default_value
+    default_value:
+      'language-interface': 0
+  negotiation/language_url/enabled:
+    plugin: default_value
+    default_value:
+      'language-url': 0
+      'language-url-fallback': 1
+  negotiation/language_interface/enabled:
+    plugin: static_map
+    source: language_negotiation
+    map:
+      # LANGUAGE_NEGOTIATION_NONE = 0
+      # LANGUAGE_NEGOTIATION_PATH_DEFAULT = 1
+      # LANGUAGE_NEGOTIATION_PATH = 2
+      # LANGUAGE_NEGOTIATION_DOMAIN = 3
+      0:
+        'language-selected': 0
+      1:
+        'language-url': 0
+        'language-selected': 1
+      2:
+        'language-url': 0
+        'language-user': 1
+        'language-browser': 2
+        'language-selected': 3
+      3:
+        'language-url': 0
+        'language-selected': 1
+destination:
+  plugin: config
+  config_name: language.types

core/modules/language/migration_templates/d7_language_negotiation_settings.yml

@@ -8,8 +8,25 @@ source:
     - locale_language_negotiation_session_param
     - locale_language_negotiation_url_part
 process:
-  'session/parameter': locale_language_negotiation_session_param
-  'url/source': locale_language_negotiation_url_part
+  session/parameter:
+    plugin: default_value
+    source: locale_language_negotiation_session_param
+    default_value: 'language'
+  selected_langcode:
+    plugin: default_value
+    default_value: 'site_default'
+  url/source:
+    plugin: static_map
+    source: locale_language_negotiation_url_part
+    default_value: path_prefix
+    map:
+      # LOCALE_LANGUAGE_NEGOTIATION_URL_PREFIX = 0
+      # LOCALE_LANGUAGE_NEGOTIATION_URL_DOMAIN = 1
+      0: path_prefix
+      1: domain
 destination:
   plugin: config
   config_name: language.negotiation
+migration_dependencies:
+  required:
+    - language

core/modules/language/migration_templates/d7_language_types.yml

@@ -0,0 +1,40 @@
+id: d7_language_types
+label: Language types
+migration_tags:
+  - Drupal 7
+source:
+  plugin: variable
+  variables:
+    - language_types
+    - language_negotiation_language
+    - language_negotiation_language_content
+    - language_negotiation_language_url
+    - locale_language_providers_weight_language
+    - locale_language_providers_weight_language_content
+    - locale_language_providers_weight_language_url
+process:
+  all:
+    plugin: language_types
+    source: language_types
+  configurable:
+    plugin: language_types
+    source: language_types
+    filter_configurable: true
+  negotiation/language_content:
+    plugin: language_negotiation
+    source:
+      - language_negotiation_language_content
+      - locale_language_providers_weight_language_content
+  negotiation/language_url:
+    plugin: language_negotiation
+    source:
+      - language_negotiation_language_url
+      - locale_language_providers_weight_language_url
+  negotiation/language_interface:
+    plugin: language_negotiation
+    source:
+      - language_negotiation_language
+      - locale_language_providers_weight_language
+destination:
+  plugin: config
+  config_name: language.types

core/modules/language/migration_templates/language_prefixes_and_domains.yml

@@ -0,0 +1,26 @@
+id: language_prefixes_and_domains
+label: Language prefixes and domains
+migration_tags:
+  - Drupal 6
+  - Drupal 7
+source:
+  plugin: language
+  fetch_all: true
+  domain_negotiation: true
+process:
+  url/prefixes:
+    plugin: array_build
+    source: languages
+    key: language
+    value: prefix
+  url/domains:
+    plugin: language_domains
+    source: languages
+    key: language
+    value: domain
+destination:
+  plugin: config
+  config_name: language.negotiation
+migration_dependencies:
+  required:
+    - language