implement configuration flag

config/install/graphql.settings.yml

@@ -0,0 +1 @@
+dataproducer_populate_default_values: true

config/schema/graphql.schema.yml

@@ -66,3 +66,13 @@ graphql.default_persisted_query_configuration:
 
 plugin.plugin_configuration.persisted_query.*:
   type: graphql.default_persisted_query_configuration
+
+graphql.settings:
+  type: config_object
+  label: "GraphQL Settings"
+  mapping:
+    # @todo Remove in GraphQL 5.
+    dataproducer_populate_default_values:
+      type: boolean
+      label: "Populate dataproducer context default values"
+      description: "Legacy setting: Populate dataproducer context default values before executing the resolve method. Set this to true to be future-proof. This setting is deprecated and will be removed in a future release."

graphql.install

@@ -69,3 +69,15 @@ function graphql_update_8001(): void {
  */
 function graphql_update_8400() :void {
 }
+
+/**
+ * Preserve dataproducer default value behavior for old installations.
+ *
+ * Set dataproducer_populate_default_values to TRUE after you verified that your
+ * dataproducers are still working with the new default value behavior.
+ */
+function graphql_update_10400() :void {
+  \Drupal::configFactory()->getEditable('graphql.settings')
+    ->set('dataproducer_populate_default_values', FALSE)
+    ->save();
+}

src/Plugin/DataProducerPluginManager.php

@@ -35,6 +35,13 @@ class DataProducerPluginManager extends DefaultPluginManager {
    */
   protected $resultCacheBackend;
 
+  /**
+   * Backwards compatibility flag to populate context defaults or not.
+   *
+   * @todo Remove in 5.x.
+   */
+  protected bool $populateContextDefaults = TRUE;
+
   /**
    * DataProducerPluginManager constructor.
    *
@@ -83,6 +90,18 @@ public function __construct(
     $this->requestStack = $requestStack;
     $this->contextsManager = $contextsManager;
     $this->resultCacheBackend = $resultCacheBackend;
+
+    // We don't use dependency injection here to avoid a constructor signature
+    // change.
+    $this->populateContextDefaults = \Drupal::config('graphql.settings')->get('dataproducer_populate_default_values', TRUE);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function createInstance($plugin_id, array $configuration = []) {
+    $configuration['dataproducer_populate_default_values'] = $this->populateContextDefaults;
+    return parent::createInstance($plugin_id, $configuration);
   }
 
   /**

src/Plugin/GraphQL/DataProducer/DataProducerPluginBase.php

@@ -50,8 +50,8 @@ public function resolveField(FieldContext $field) {
     if (!method_exists($this, 'resolve')) {
       throw new \LogicException('Missing data producer resolve method.');
     }
-
-    $context = $this->getContextValuesWithDefaults();
+    $populateDefaulktValues = $this->configuration['dataproducer_populate_default_values'] ?? TRUE;
+    $context = $populateDefaulktValues ? $this->getContextValuesWithDefaults() : $this->getContextValues();
     return call_user_func_array(
       [$this, 'resolve'],
       array_values(array_merge($context, [$field]))