diff --git a/core/modules/block_content/config/schema/block_content.schema.yml b/core/modules/block_content/config/schema/block_content.schema.yml
index a39fda4..2e7c338 100644
--- a/core/modules/block_content/config/schema/block_content.schema.yml
+++ b/core/modules/block_content/config/schema/block_content.schema.yml
@@ -16,4 +16,3 @@ block_content.type.*:
     description:
       type: text
       label: 'Description'
-
diff --git a/core/modules/file/src/Plugin/migrate/source/d7/File.php b/core/modules/file/src/Plugin/migrate/source/d7/File.php
index 93d92e4..d54c258 100644
--- a/core/modules/file/src/Plugin/migrate/source/d7/File.php
+++ b/core/modules/file/src/Plugin/migrate/source/d7/File.php
@@ -89,8 +89,8 @@ public function prepareRow(Row $row) {
     // At this point, $path could be an absolute path or a relative path,
     // depending on how the scheme's variable was set. So we need to shear out
     // the source_base_path in order to make them all relative.
-    // @todo Don't depend on destination configuration and figure out if this is
-    // even needed at all? https://www.drupal.org/node/2577871
+    // @todo https://www.drupal.org/node/2577871 Don't depend on destination
+    //   configuration and figure out if this is even needed at all?
     $path = str_replace($this->migration->get('destination')['source_base_path'], NULL, $path);
     $row->setSourceProperty('filepath', $path);
     return parent::prepareRow($row);
diff --git a/core/modules/migrate/src/Entity/MigrationInterface.php b/core/modules/migrate/src/Entity/MigrationInterface.php
index 1c8eb60..b35cf29 100644
--- a/core/modules/migrate/src/Entity/MigrationInterface.php
+++ b/core/modules/migrate/src/Entity/MigrationInterface.php
@@ -7,10 +7,13 @@
 
 namespace Drupal\migrate\Entity;
 
+use Drupal\Component\Plugin\DerivativeInspectionInterface;
+use Drupal\Component\Plugin\PluginInspectionInterface;
+
 /**
  * Interface for migrations.
  */
-interface MigrationInterface {
+interface MigrationInterface extends PluginInspectionInterface, DerivativeInspectionInterface {
 
   /**
    * A constant used for systemOfRecord.
@@ -101,6 +104,9 @@
    * An alias for getPluginId() for backwards compatibility reasons.
    *
    * @return string
+   *   The plugin_id of the plugin instance.
+   *
+   * @see \Drupal\migrate\Entity\MigrationInterface::getPluginId()
    */
   public function id();
 
diff --git a/core/modules/migrate/src/MigrateExecutable.php b/core/modules/migrate/src/MigrateExecutable.php
index 24c4711..7f9b00d 100644
--- a/core/modules/migrate/src/MigrateExecutable.php
+++ b/core/modules/migrate/src/MigrateExecutable.php
@@ -29,7 +29,7 @@ class MigrateExecutable implements MigrateExecutableInterface {
   /**
    * The configuration of the migration to do.
    *
-   * @var \Drupal\migrate\Plugin\Migration
+   * @var \Drupal\migrate\Entity\MigrationInterface
    */
   protected $migration;
 
diff --git a/core/modules/migrate/src/Plugin/Migration.php b/core/modules/migrate/src/Plugin/Migration.php
index 25c61bc..0e1fd16 100644
--- a/core/modules/migrate/src/Plugin/Migration.php
+++ b/core/modules/migrate/src/Plugin/Migration.php
@@ -19,7 +19,6 @@
  *
  * The migration entity stores the information about a single migration, like
  * the source, process and destination plugins.
- *
  */
 class Migration extends PluginBase implements MigrationInterface, RequirementsInterface {
 
@@ -257,7 +256,7 @@ public function label() {
   }
 
   /**
-   * Gets any arbitrary property.
+   * Gets any arbitrary property's value.
    *
    * @param string $property
    *   The property to retrieve.
@@ -265,8 +264,8 @@ public function label() {
    * @return mixed
    *   The value for that property, or NULL if the property does not exist.
    */
-  public function get($key) {
-    return isset($this->$key) ? $this->$key : NULL;
+  public function get($property) {
+    return isset($this->$property) ? $this->$property : NULL;
   }
 
   /**
diff --git a/core/modules/migrate/src/Plugin/MigrationDeriverTrait.php b/core/modules/migrate/src/Plugin/MigrationDeriverTrait.php
index 00e4fab..c1a6eff 100644
--- a/core/modules/migrate/src/Plugin/MigrationDeriverTrait.php
+++ b/core/modules/migrate/src/Plugin/MigrationDeriverTrait.php
@@ -15,11 +15,8 @@
   /**
    * Returns a fully initialized instance of a source plugin.
    *
-   * @param string $plugin_id
-   *   The plugin ID.
-   * @param array $configuration
-   *   (optional) Additional configuration for the plugin. Defaults to an empty
-   *   array.
+   * @param string $source_plugin_id
+   *   The source plugin ID.
    *
    * @return \Drupal\migrate\Plugin\MigrateSourceInterface|\Drupal\migrate\Plugin\RequirementsInterface
    *   The fully initialized source plugin.
diff --git a/core/modules/migrate/src/Plugin/MigrationPluginManagerInterface.php b/core/modules/migrate/src/Plugin/MigrationPluginManagerInterface.php
index 87ec3c6..02d329b 100644
--- a/core/modules/migrate/src/Plugin/MigrationPluginManagerInterface.php
+++ b/core/modules/migrate/src/Plugin/MigrationPluginManagerInterface.php
@@ -10,7 +10,7 @@
 use Drupal\Component\Plugin\PluginManagerInterface;
 
 /**
- * Migration plugin manager interface
+ * Migration plugin manager interface.
  */
 interface MigrationPluginManagerInterface extends PluginManagerInterface {
 
diff --git a/core/modules/migrate/src/Tests/MigrateTestBase.php b/core/modules/migrate/src/Tests/MigrateTestBase.php
index 2b956ee..19bf66b 100644
--- a/core/modules/migrate/src/Tests/MigrateTestBase.php
+++ b/core/modules/migrate/src/Tests/MigrateTestBase.php
@@ -227,7 +227,13 @@ protected function mockFailure($migration, array $row, $status = MigrateIdMapInt
   }
 
   /**
+   * Gets the migration plugin.
+   *
+   * @param $plugin_id
+   *   The plugin ID of the migration to get.
+   *
    * @return \Drupal\migrate\Plugin\Migration
+   *   The migration plugin.
    */
   protected function getMigration($plugin_id) {
     return $this->container->get('plugin.manager.migration')->createInstance($plugin_id);
diff --git a/core/modules/migrate/src/Tests/MigrationTest.php b/core/modules/migrate/src/Tests/MigrationTest.php
index 8eeaa0e..998337d 100644
--- a/core/modules/migrate/src/Tests/MigrationTest.php
+++ b/core/modules/migrate/src/Tests/MigrationTest.php
@@ -14,6 +14,7 @@
  * Tests the migration plugin.
  *
  * @group migrate
+ *
  * @coversDefaultClass \Drupal\migrate\Plugin\Migration
  */
 class MigrationTest extends KernelTestBase {
diff --git a/core/modules/migrate/tests/src/Unit/MigrationTest.php b/core/modules/migrate/tests/src/Unit/MigrationTest.php
index a1d28af..b338fce 100644
--- a/core/modules/migrate/tests/src/Unit/MigrationTest.php
+++ b/core/modules/migrate/tests/src/Unit/MigrationTest.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\Tests\migrate\Unit;
 
-use Drupal\Core\Entity\EntityManagerInterface;
 use Drupal\migrate\Plugin\Migration;
 use Drupal\migrate\Exception\RequirementsException;
 use Drupal\migrate\Plugin\MigrateDestinationInterface;
@@ -18,6 +17,7 @@
 
 /**
  * @coversDefaultClass \Drupal\migrate\Plugin\Migration
+ *
  * @group Migration
  */
 class MigrationTest extends UnitTestCase {
diff --git a/core/modules/migrate_drupal/src/MigrationCreationTrait.php b/core/modules/migrate_drupal/src/MigrationCreationTrait.php
index daabc56..7e92e51 100644
--- a/core/modules/migrate_drupal/src/MigrationCreationTrait.php
+++ b/core/modules/migrate_drupal/src/MigrationCreationTrait.php
@@ -39,8 +39,8 @@ protected function getConnection(array $database) {
   /**
    * Gets the system data from the system table of the source Drupal database.
    *
-   * @param array $database
-   *   Database array representing the source Drupal database.
+   * @param \Drupal\Core\Database\Connection $connection
+   *   Database connection to the source Drupal database.
    *
    * @return array
    *   The system data from the system table of the source Drupal database.
diff --git a/core/modules/migrate_drupal/src/Plugin/migrate/CckMigration.php b/core/modules/migrate_drupal/src/Plugin/migrate/CckMigration.php
index 42cec25..e18e20c 100644
--- a/core/modules/migrate_drupal/src/Plugin/migrate/CckMigration.php
+++ b/core/modules/migrate_drupal/src/Plugin/migrate/CckMigration.php
@@ -59,6 +59,8 @@ class CckMigration extends Migration implements ContainerFactoryPluginInterface
    *   The plugin definition.
    * @param \Drupal\migrate\Plugin\MigratePluginManager $cck_manager
    *   The cckfield plugin manager.
+   * @param \Drupal\migrate\Plugin\MigrationPluginManagerInterface $migration_plugin_manager
+   *   The migration plugin manager.
    */
   public function __construct(array $configuration, $plugin_id, $plugin_definition, MigratePluginManager $cck_manager, MigrationPluginManagerInterface $migration_plugin_manager) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
@@ -99,8 +101,8 @@ public function getProcess() {
         $field_type = $row->getSourceProperty('type');
         if (!isset($this->processedFieldTypes[$field_type]) && $this->cckPluginManager->hasDefinition($field_type)) {
           $this->processedFieldTypes[$field_type] = TRUE;
-          // Allow the cckfield plugin to alter the migration as necessary so that
-          // it knows how to handle fields of this type.
+          // Allow the cckfield plugin to alter the migration as necessary so
+          // that it knows how to handle fields of this type.
           if (!isset($this->cckPluginCache[$field_type])) {
             $this->cckPluginCache[$field_type] = $this->cckPluginManager->createInstance($field_type, [], $this);
           }
diff --git a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
index f64549d..59f28b5 100644
--- a/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
+++ b/core/modules/migrate_drupal_ui/src/Form/MigrateUpgradeForm.php
@@ -972,7 +972,8 @@ public function validateCredentialForm(array &$form, FormStateInterface $form_st
 
         // Store the retrived system data in from storage.
         $form_state->set('system_data', $system_data);
-      } catch (\Exception $e) {
+      }
+      catch (\Exception $e) {
         $error_message = [
           '#type' => 'inline_template',
           '#template' => '{% trans %}Resolve the issue below to continue the upgrade.{% endtrans%}{{ errors }}',
diff --git a/core/modules/node/src/Plugin/migrate/D6NodeDeriver.php b/core/modules/node/src/Plugin/migrate/D6NodeDeriver.php
index 97c9329..109b8f1 100644
--- a/core/modules/node/src/Plugin/migrate/D6NodeDeriver.php
+++ b/core/modules/node/src/Plugin/migrate/D6NodeDeriver.php
@@ -22,9 +22,11 @@ class D6NodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   use MigrationDeriverTrait;
 
   /**
-   * @var bool
+   * The base plugin ID this derivative is for.
+   *
+   * @var string
    */
-  protected $init = FALSE;
+  protected $basePluginId;
 
   /**
    * Already-instantiated cckfield plugins, keyed by ID.
@@ -34,6 +36,8 @@ class D6NodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   protected $cckPluginCache;
 
   /**
+   * The CCK plugin manager.
+   *
    * @var \Drupal\Component\Plugin\PluginManagerInterface
    */
   protected $cckPluginManager;
@@ -41,8 +45,10 @@ class D6NodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   /**
    * D6NodeDeriver constructor.
    *
-   * @param $base_plugin_id
+   * @param string $base_plugin_id
+   *   The base plugin ID for the plugin ID.
    * @param \Drupal\Component\Plugin\PluginManagerInterface $cck_manager
+   *   The CCK plugin manager.
    */
   public function __construct($base_plugin_id, PluginManagerInterface $cck_manager) {
     $this->basePluginId = $base_plugin_id;
@@ -64,10 +70,11 @@ public static function create(ContainerInterface $container, $base_plugin_id) {
    *
    * @param array $base_plugin_definition
    *   The definition array of the base plugin.
+   *
    * @return array
    *   An array of full derivative definitions keyed on derivative id.
    *
-   * @see getDerivativeDefinition()
+   * @see \Drupal\Component\Plugin\Derivative\DeriverBase::getDerivativeDefinition()
    */
   public function getDerivativeDefinitions($base_plugin_definition) {
     // Read all CCK field instance definitions in the source database.
@@ -93,12 +100,12 @@ public function getDerivativeDefinitions($base_plugin_definition) {
         $label = $base_plugin_definition['label'];
         $values['label'] = t("@label (@type)", [
           '@label' => $label,
-          '@type' => $node_type
+          '@type' => $node_type,
         ]);
         $values['source']['node_type'] = $node_type;
 
-        // If this migration is based on the d6_node_revision template, it should
-        // explicitly depend on the corresponding d6_node variant.
+        // If this migration is based on the d6_node_revision template, it
+        // should explicitly depend on the corresponding d6_node variant.
         if ($base_plugin_definition['id'] == 'd6_node_revision') {
           $values['migration_dependencies']['required'][] = 'd6_node:' . $node_type;
         }
diff --git a/core/modules/node/src/Plugin/migrate/D7NodeDeriver.php b/core/modules/node/src/Plugin/migrate/D7NodeDeriver.php
index cfbd663..9d45254 100644
--- a/core/modules/node/src/Plugin/migrate/D7NodeDeriver.php
+++ b/core/modules/node/src/Plugin/migrate/D7NodeDeriver.php
@@ -21,9 +21,11 @@ class D7NodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   use MigrationDeriverTrait;
 
   /**
-   * @var bool
+   * The base plugin ID this derivative is for.
+   *
+   * @var string
    */
-  protected $init = FALSE;
+  protected $basePluginId;
 
   /**
    * Already-instantiated cckfield plugins, keyed by ID.
@@ -33,6 +35,8 @@ class D7NodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   protected $cckPluginCache;
 
   /**
+   * The CCK plugin manager.
+   *
    * @var \Drupal\Component\Plugin\PluginManagerInterface
    */
   protected $cckPluginManager;
@@ -40,8 +44,10 @@ class D7NodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   /**
    * D7NodeDeriver constructor.
    *
-   * @param $base_plugin_id
+   * @param string $base_plugin_id
+   *   The base plugin ID for the plugin ID.
    * @param \Drupal\Component\Plugin\PluginManagerInterface $cck_manager
+   *   The CCK plugin manager.
    */
   public function __construct($base_plugin_id, PluginManagerInterface $cck_manager) {
     $this->basePluginId = $base_plugin_id;
@@ -78,7 +84,7 @@ public function getDerivativeDefinitions($base_plugin_definition) {
 
         $values['label'] = t('@label (@type)', [
           '@label' => $values['label'],
-          '@type' => $row->getSourceProperty('name')
+          '@type' => $row->getSourceProperty('name'),
         ]);
         $values['source']['node_type'] = $node_type;
 
@@ -108,5 +114,4 @@ public function getDerivativeDefinitions($base_plugin_definition) {
     return $this->derivatives;
   }
 
-
 }
diff --git a/core/modules/taxonomy/src/Plugin/migrate/D6TermNodeDeriver.php b/core/modules/taxonomy/src/Plugin/migrate/D6TermNodeDeriver.php
index 539be68..245c026 100644
--- a/core/modules/taxonomy/src/Plugin/migrate/D6TermNodeDeriver.php
+++ b/core/modules/taxonomy/src/Plugin/migrate/D6TermNodeDeriver.php
@@ -19,8 +19,28 @@
 class D6TermNodeDeriver extends DeriverBase implements ContainerDeriverInterface {
   use MigrationDeriverTrait;
 
+  /**
+   * The base plugin ID this derivative is for.
+   *
+   * @var string
+   */
   protected $basePluginId;
 
+  /**
+   * The migration plugin manager.
+   *
+   * @var \Drupal\Component\Plugin\PluginManagerInterface
+   */
+  protected $migrationPluginManager;
+
+  /**
+   * D6TermNodeDeriver constructor.
+   *
+   * @param string $base_plugin_id
+   *   The base plugin ID this derivative is for.
+   * @param \Drupal\Component\Plugin\PluginManagerInterface $migration_plugin_manager
+   *   The migration plugin manager.
+   */
   public function __construct($base_plugin_id, PluginManagerInterface $migration_plugin_manager) {
     $this->basePluginId = $base_plugin_id;
     $this->migrationPluginManager = $migration_plugin_manager;
@@ -55,5 +75,4 @@ public function getDerivativeDefinitions($base_plugin_definition, $base_plugin_d
     return $this->derivatives;
   }
 
-
 }
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 92510aa..ddca901 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
@@ -27,5 +27,3 @@ destination:
 migration_dependencies:
   required:
     - vocabularies
-
-
diff --git a/core/modules/user/src/Plugin/migrate/ProfileValues.php b/core/modules/user/src/Plugin/migrate/ProfileValues.php
index 202e3c4..9beeb44 100644
--- a/core/modules/user/src/Plugin/migrate/ProfileValues.php
+++ b/core/modules/user/src/Plugin/migrate/ProfileValues.php
@@ -16,6 +16,8 @@
 class ProfileValues extends Migration {
 
   /**
+   * Flag determining whether the process plugin has been initialized.
+   *
    * @var bool
    */
   protected $init = FALSE;
diff --git a/core/modules/user/src/Tests/Migrate/d7/UserMigrationClassTest.php b/core/modules/user/src/Tests/Migrate/d7/UserMigrationClassTest.php
index 04d00c3..a804638 100644
--- a/core/modules/user/src/Tests/Migrate/d7/UserMigrationClassTest.php
+++ b/core/modules/user/src/Tests/Migrate/d7/UserMigrationClassTest.php
@@ -17,8 +17,10 @@
 class UserMigrationClassTest extends MigrateDrupal7TestBase {
 
   /**
-   * Tests that profile fields are merged into the d6_profile_values migration's
-   * process pipeline by the d6_profile_values builder.
+   * Tests d6_profile_values builder.
+   *
+   * Ensures profile fields are merged into the d6_profile_values migration's
+   * process pipeline.
    */
   public function testClass() {
     $migration = $this->getMigration('d7_user');