Issue #3514034: Do not completely split items depending on patched ones

Closes #3514034

src/ConfigSplitManager.php

@@ -314,6 +314,7 @@ public function splitPreview(ImmutableConfig $config, StorageInterface $transfor
     $modules = array_keys($config->get('module'));
     $changes = $this->manager->getConfigEntitiesToChangeOnDependencyRemoval('module', $modules, TRUE);
 
+    $changes = $this->reprocessDeletions($changes);
     $this->processEntitiesToChangeOnDependencyRemoval($changes, $source, $transforming, $splitStorage);
 
     $completelySplit = array_map(function (ConfigEntityInterface $entity) {
@@ -346,6 +347,7 @@ public function splitPreview(ImmutableConfig $config, StorageInterface $transfor
 
       // Process also the config being removed.
       $changes = $this->manager->getConfigEntitiesToChangeOnDependencyRemoval('config', $completeList, TRUE);
+      $changes = $this->reprocessDeletions($changes, $completeSplitList);
       $this->processEntitiesToChangeOnDependencyRemoval($changes, $source, $transforming, $splitStorage);
 
       // Split all the config which was specified but not processed yet.
@@ -423,6 +425,60 @@ public function splitPreview(ImmutableConfig $config, StorageInterface $transfor
     $transforming->write('core.extension', $extensions);
   }
 
+  /**
+   * Reprocesses changes to include only actual deletions.
+   *
+   * To compute items needing patching, config items are flagged as being
+   * removed: this may cause config items depending on those to be flagged as
+   * needing removal as well, whereas they may actually be unaffected. This
+   * recalculates dependencies for items flagged for removal to confirm it is
+   * actually required.
+   *
+   * @param string[][] $changes
+   *   An associative array keyed by change type of config item name arrays.
+   * @param string[] $legit_deletions
+   *   (optional) An array of config item names which should legitimately be
+   *   deleted.
+   *
+   * @return string[][]
+   *   The reprocessed changes array.
+   */
+  protected function reprocessDeletions(array $changes, array $legit_deletions = []): array {
+    if (!$changes['delete']) {
+      return $changes;
+    }
+
+    // Collect updated configuration dependencies and check whether any of them
+    // is a dependency of items flagged for removal, in which case the latter
+    // need to be double-checked.
+    $key_array = fn (array $array) => array_combine(array_map(fn (ConfigEntityInterface $entity) => $entity->getConfigDependencyName(), $array), $array);
+    $deleted_config = $key_array($changes['delete']);
+    $updated_config = $key_array($changes['update']);
+    $updated_dependencies = $this->manager->findConfigEntityDependencies('config', array_keys($updated_config));
+    $actually_deleted_config = array_merge(array_diff_key($deleted_config, $updated_dependencies), array_flip($legit_deletions));
+    $actually_updated_config = array_diff_key($deleted_config, $actually_deleted_config);
+
+    // Collect dependencies of the config items being re-evaluated to confirm
+    // none of them is flagged for removal.
+    $actually_updated_dependencies = [];
+    foreach (array_map(fn (ConfigEntityInterface $entity) => $entity->getDependencies(), $actually_updated_config) as $dependency) {
+      if (!empty($dependency['config'])) {
+        $actually_updated_dependencies += array_flip($dependency['config']);
+      }
+    }
+    $actually_deleted_config = array_diff_key($actually_deleted_config, $actually_updated_dependencies);
+
+    // Update the list of legit config item updates and deletions based on the
+    // findings above.
+    $actually_updated_config = array_diff_key($deleted_config, $actually_deleted_config);
+    if ($actually_updated_config) {
+      $changes['update'] = array_values($updated_config + $actually_updated_config);
+      $changes['delete'] = array_values(array_intersect_key($deleted_config, $actually_deleted_config));
+    }
+
+    return $changes;
+  }
+
   /**
    * Merge the config of a split to the transformation storage.
    *