Issue #3477442 by tr: Parameter typing in DataFetcher service

src/DataFetcher.php

 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\typed_data;
 
 use Drupal\Core\Cache\CacheableDependencyInterface;
@@ -27,7 +29,7 @@ class DataFetcher implements DataFetcherInterface {
   /**
    * {@inheritdoc}
    */
-  public function fetchDataByPropertyPath(TypedDataInterface $typed_data, string $property_path, BubbleableMetadata $bubbleable_metadata = NULL, string $langcode = NULL): TypedDataInterface {
+  public function fetchDataByPropertyPath(TypedDataInterface $typed_data, string $property_path, ?BubbleableMetadata $bubbleable_metadata = NULL, ?string $langcode = NULL): TypedDataInterface {
     $sub_paths = explode('.', $property_path);
     return $this->fetchDataBySubPaths($typed_data, $sub_paths, $bubbleable_metadata, $langcode);
   }
@@ -35,7 +37,7 @@ class DataFetcher implements DataFetcherInterface {
   /**
    * {@inheritdoc}
    */
-  public function fetchDataBySubPaths(TypedDataInterface $typed_data, array $sub_paths, BubbleableMetadata $bubbleable_metadata = NULL, string $langcode = NULL): TypedDataInterface {
+  public function fetchDataBySubPaths(TypedDataInterface $typed_data, array $sub_paths, ?BubbleableMetadata $bubbleable_metadata = NULL, ?string $langcode = NULL): TypedDataInterface {
     $current_selector = [];
     $bubbleable_metadata = $bubbleable_metadata ?: new BubbleableMetadata();
 
@@ -104,7 +106,7 @@ class DataFetcher implements DataFetcherInterface {
   /**
    * {@inheritdoc}
    */
-  public function fetchDefinitionByPropertyPath(DataDefinitionInterface $data_definition, string $property_path, string $langcode = NULL): DataDefinitionInterface {
+  public function fetchDefinitionByPropertyPath(DataDefinitionInterface $data_definition, string $property_path, ?string $langcode = NULL): DataDefinitionInterface {
     $sub_paths = explode('.', $property_path);
     return $this->fetchDefinitionBySubPaths($data_definition, $sub_paths, $langcode);
   }
@@ -112,7 +114,7 @@ class DataFetcher implements DataFetcherInterface {
   /**
    * {@inheritdoc}
    */
-  public function fetchDefinitionBySubPaths(DataDefinitionInterface $data_definition, array $sub_paths, string $langcode = NULL): DataDefinitionInterface {
+  public function fetchDefinitionBySubPaths(DataDefinitionInterface $data_definition, array $sub_paths, ?string $langcode = NULL): DataDefinitionInterface {
     $current_selector = [];
 
     foreach ($sub_paths as $name) {

src/DataFetcherInterface.php

@@ -34,7 +34,7 @@ interface DataFetcherInterface {
    *   Thrown if the given path is not valid for the given data; e.g., a not
    *   existing property is referenced.
    */
-  public function fetchDataByPropertyPath(TypedDataInterface $typed_data, string $property_path, BubbleableMetadata $bubbleable_metadata = NULL, string $langcode = NULL): TypedDataInterface;
+  public function fetchDataByPropertyPath(TypedDataInterface $typed_data, string $property_path, ?BubbleableMetadata $bubbleable_metadata = NULL, ?string $langcode = NULL): TypedDataInterface;
 
   /**
    * Fetches data based upon the given sub-paths.
@@ -59,7 +59,7 @@ interface DataFetcherInterface {
    *   Thrown if the given path is not valid for the given data; e.g., a non-
    *   existent property is referenced.
    */
-  public function fetchDataBySubPaths(TypedDataInterface $typed_data, array $sub_paths, BubbleableMetadata $bubbleable_metadata = NULL, string $langcode = NULL): TypedDataInterface;
+  public function fetchDataBySubPaths(TypedDataInterface $typed_data, array $sub_paths, ?BubbleableMetadata $bubbleable_metadata = NULL, ?string $langcode = NULL): TypedDataInterface;
 
   /**
    * Fetches a data definition based upon the given property path.
@@ -79,7 +79,7 @@ interface DataFetcherInterface {
    *   Thrown if the given path is not valid for the given data; e.g., a not
    *   existing property is referenced.
    */
-  public function fetchDefinitionByPropertyPath(DataDefinitionInterface $data_definition, string $property_path, string $langcode = NULL): DataDefinitionInterface;
+  public function fetchDefinitionByPropertyPath(DataDefinitionInterface $data_definition, string $property_path, ?string $langcode = NULL): DataDefinitionInterface;
 
   /**
    * Fetches a data definition based upon the given sub-paths.
@@ -99,7 +99,7 @@ interface DataFetcherInterface {
    *   Thrown if the given path is not valid for the given data; e.g., a not
    *   existing property is referenced.
    */
-  public function fetchDefinitionBySubPaths(DataDefinitionInterface $data_definition, array $sub_paths, string $langcode = NULL): DataDefinitionInterface;
+  public function fetchDefinitionBySubPaths(DataDefinitionInterface $data_definition, array $sub_paths, ?string $langcode = NULL): DataDefinitionInterface;
 
   /**
    * Provides autocomplete suggestions for an incomplete property path.

src/DataFetcherTrait.php

 <?php
 
+declare(strict_types=1);
+
 namespace Drupal\typed_data;
 
 /**