diff --git a/core/lib/Drupal/Core/Block/BlockBase.php b/core/lib/Drupal/Core/Block/BlockBase.php
index 03d76ac..bcc3954 100644
--- a/core/lib/Drupal/Core/Block/BlockBase.php
+++ b/core/lib/Drupal/Core/Block/BlockBase.php
@@ -10,6 +10,7 @@
 use Drupal\Component\Utility\Unicode;
 use Drupal\Component\Utility\NestedArray;
 use Drupal\Core\Language\LanguageInterface;
+use Drupal\Core\Plugin\PluginWithFormsInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Component\Transliteration\TransliterationInterface;
 
@@ -22,7 +23,7 @@
  *
  * @ingroup block_api
  */
-abstract class BlockBase extends ContextAwarePluginBase implements BlockPluginInterface {
+abstract class BlockBase extends ContextAwarePluginBase implements BlockPluginInterface, PluginWithFormsInterface {
 
   use ContextAwarePluginAssignmentTrait;
 
@@ -271,4 +272,20 @@ public function setTransliteration(TransliterationInterface $transliteration) {
     $this->transliteration = $transliteration;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormClass($operation) {
+    if ($this->hasFormClass($operation)) {
+      return $this->getPluginDefinition()['forms'][$operation];
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function hasFormClass($operation) {
+    return isset($this->getPluginDefinition()['forms'][$operation]);
+  }
+
 }
diff --git a/core/lib/Drupal/Core/Plugin/PluginFormFactory.php b/core/lib/Drupal/Core/Plugin/PluginFormFactory.php
index addd0cc..6cbbc22 100644
--- a/core/lib/Drupal/Core/Plugin/PluginFormFactory.php
+++ b/core/lib/Drupal/Core/Plugin/PluginFormFactory.php
@@ -4,7 +4,6 @@
 
 use Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException;
 use Drupal\Component\Plugin\PluginAwareInterface;
-use Drupal\Component\Plugin\PluginInspectionInterface;
 use Drupal\Core\DependencyInjection\ClassResolverInterface;
 
 /**
@@ -32,10 +31,10 @@ public function __construct(ClassResolverInterface $class_resolver) {
   /**
    * {@inheritdoc}
    */
-  public function createInstance(PluginInspectionInterface $plugin, $operation, $fallback_operation = NULL) {
-    if (!$this->hasForm($plugin, $operation)) {
+  public function createInstance(PluginWithFormsInterface $plugin, $operation, $fallback_operation = NULL) {
+    if (!$plugin->hasFormClass($operation)) {
       // Use the default form class if no form is specified for this operation.
-      if ($fallback_operation && $this->hasForm($plugin, $fallback_operation)) {
+      if ($fallback_operation && $plugin->hasFormClass($fallback_operation)) {
         $operation = $fallback_operation;
       }
       else {
@@ -43,7 +42,7 @@ public function createInstance(PluginInspectionInterface $plugin, $operation, $f
       }
     }
 
-    $form_class = $this->getFormClass($plugin, $operation);
+    $form_class = $plugin->getFormClass($operation);
 
     // If the form specified is the plugin itself, use it directly.
     if (ltrim(get_class($plugin), '\\') === ltrim($form_class, '\\')) {
@@ -65,27 +64,4 @@ public function createInstance(PluginInspectionInterface $plugin, $operation, $f
     return $form_object;
   }
 
-  /**
-   * {@inheritdoc}
-   */
-  public function hasForm(PluginInspectionInterface $plugin, $operation) {
-    return isset($plugin->getPluginDefinition()['forms'][$operation]);
-  }
-
-  /**
-   * Gets the plugin form class for a specific operation.
-   *
-   * @param \Drupal\Component\Plugin\PluginInspectionInterface $plugin
-   *   The plugin the form is for.
-   * @param string $operation
-   *   The name of the operation to use, e.g., 'add' or 'edit'.
-   *
-   * @return null|string
-   */
-  protected function getFormClass(PluginInspectionInterface $plugin, $operation) {
-    if ($this->hasForm($plugin, $operation)) {
-      return $plugin->getPluginDefinition()['forms'][$operation];
-    }
-  }
-
 }
diff --git a/core/lib/Drupal/Core/Plugin/PluginFormFactoryInterface.php b/core/lib/Drupal/Core/Plugin/PluginFormFactoryInterface.php
index b2e6b09..d556269 100644
--- a/core/lib/Drupal/Core/Plugin/PluginFormFactoryInterface.php
+++ b/core/lib/Drupal/Core/Plugin/PluginFormFactoryInterface.php
@@ -18,7 +18,7 @@
   /**
    * Creates a new form instance.
    *
-   * @param \Drupal\Component\Plugin\PluginInspectionInterface $plugin
+   * @param \Drupal\Core\Plugin\PluginWithFormsInterface $plugin
    *   The plugin the form is for.
    * @param string $operation
    *   The name of the operation to use, e.g., 'add' or 'edit'.
@@ -30,19 +30,6 @@
    *
    * @throws \Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException
    */
-  public function createInstance(PluginInspectionInterface $plugin, $operation, $fallback_operation = NULL);
-
-  /**
-   * Determines if a given plugin has a form for the specified operation.
-   *
-   * @param \Drupal\Component\Plugin\PluginInspectionInterface $plugin
-   *   The plugin the form is for.
-   * @param string $operation
-   *   The name of the operation to use, e.g., 'add' or 'edit'.
-   *
-   * @return bool
-   *   Returns TRUE if the plugin has a form for the operation.
-   */
-  public function hasForm(PluginInspectionInterface $plugin, $operation);
+  public function createInstance(PluginWithFormsInterface $plugin, $operation, $fallback_operation = NULL);
 
 }
diff --git a/core/lib/Drupal/Core/Plugin/PluginWithFormsInterface.php b/core/lib/Drupal/Core/Plugin/PluginWithFormsInterface.php
new file mode 100644
index 0000000..b6beeab
--- /dev/null
+++ b/core/lib/Drupal/Core/Plugin/PluginWithFormsInterface.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Drupal\commerce\PluginForm;
+
+use Drupal\Component\Plugin\PluginInspectionInterface;
+
+/**
+ * Provides an interface for plugins which have forms.
+ *
+ * Plugin forms are embeddable forms referenced by the plugin annotation.
+ * Used by plugin types which have a larger number of plugin-specific forms.
+ */
+interface PluginWithFormsInterface extends PluginInspectionInterface {
+
+  /**
+   * Gets the form class for the given operation.
+   *
+   * @param string $operation
+   *   The name of the operation.
+   *
+   * @return string|null
+   *   The form class if defined, NULL otherwise.
+   */
+  public function getFormClass($operation);
+
+  /**
+   * Gets whether the plugin has a form class for the given operation.
+   *
+   * @param string $operation
+   *   The name of the operation.
+   *
+   * @return bool
+   *   TRUE if the plugin has a form class for the given operation.
+   */
+  public function hasFormClass($operation);
+
+}
diff --git a/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestMultipleFormsBlock.php b/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestMultipleFormsBlock.php
index 87708c2..64b70b2 100644
--- a/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestMultipleFormsBlock.php
+++ b/core/modules/block/tests/modules/block_test/src/Plugin/Block/TestMultipleFormsBlock.php
@@ -9,7 +9,7 @@
  *
  * @Block(
  *   id = "test_multiple_forms_block",
- *   form = {
+ *   forms = {
  *     "secondary" = "\Drupal\block_test\PluginForm\EmptyBlockForm"
  *   },
  *   admin_label = @Translation("Multiple forms test block")
diff --git a/core/tests/Drupal/Tests/Core/Plugin/PluginFormFactoryTest.php b/core/tests/Drupal/Tests/Core/Plugin/PluginFormFactoryTest.php
index efd8920..fc4b77a 100644
--- a/core/tests/Drupal/Tests/Core/Plugin/PluginFormFactoryTest.php
+++ b/core/tests/Drupal/Tests/Core/Plugin/PluginFormFactoryTest.php
@@ -4,10 +4,10 @@
 
 use Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException;
 use Drupal\Component\Plugin\PluginAwareInterface;
-use Drupal\Component\Plugin\PluginInspectionInterface;
 use Drupal\Core\DependencyInjection\ClassResolverInterface;
 use Drupal\Core\Plugin\PluginFormInterface;
 use Drupal\Core\Plugin\PluginFormFactory;
+use Drupal\Core\Plugin\PluginWithFormsInterface;
 use Drupal\Tests\UnitTestCase;
 use Prophecy\Argument;
 
@@ -42,24 +42,6 @@ protected function setUp() {
   }
 
   /**
-   * @covers ::hasForm
-   */
-  public function testHasForm() {
-    $plugin_form = $this->prophesize(PluginFormInterface::class);
-    $expected = $plugin_form->reveal();
-
-    $plugin = $this->prophesize(PluginInspectionInterface::class);
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'standard_class' => get_class($expected),
-      ],
-    ]);
-
-    $result = $this->manager->hasForm($plugin->reveal(), 'standard_class');
-    $this->assertTrue($result);
-  }
-
-  /**
    * @covers ::createInstance
    */
   public function testCreateInstance() {
@@ -68,12 +50,9 @@ public function testCreateInstance() {
 
     $this->classResolver->getInstanceFromDefinition(get_class($expected))->willReturn($expected);
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class);
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'standard_class' => get_class($expected),
-      ],
-    ]);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class);
+    $plugin->hasFormClass('standard_class')->willReturn(TRUE);
+    $plugin->getFormClass('standard_class')->willReturn(get_class($expected));
 
     $form_object = $this->manager->createInstance($plugin->reveal(), 'standard_class');
     $this->assertSame($expected, $form_object);
@@ -85,12 +64,9 @@ public function testCreateInstance() {
   public function testCreateInstanceUsingPlugin() {
     $this->classResolver->getInstanceFromDefinition(Argument::cetera())->shouldNotBeCalled();
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class)->willImplement(PluginFormInterface::class);
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'configure' => get_class($plugin->reveal()),
-      ],
-    ]);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class)->willImplement(PluginFormInterface::class);
+    $plugin->hasFormClass('configure')->willReturn(TRUE);
+    $plugin->getFormClass('configure')->willReturn(get_class($plugin->reveal()));
 
     $form_object = $this->manager->createInstance($plugin->reveal(), 'configure');
     $this->assertSame($plugin->reveal(), $form_object);
@@ -102,12 +78,9 @@ public function testCreateInstanceUsingPlugin() {
   public function testCreateInstanceUsingPluginWithSlashes() {
     $this->classResolver->getInstanceFromDefinition(Argument::cetera())->shouldNotBeCalled();
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class)->willImplement(PluginFormInterface::class);
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'configure' => '\\' . get_class($plugin->reveal()),
-      ],
-    ]);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class)->willImplement(PluginFormInterface::class);
+    $plugin->hasFormClass('configure')->willReturn(TRUE);
+    $plugin->getFormClass('configure')->willReturn('\\' . get_class($plugin->reveal()));
 
     $form_object = $this->manager->createInstance($plugin->reveal(), 'configure');
     $this->assertSame($plugin->reveal(), $form_object);
@@ -119,12 +92,10 @@ public function testCreateInstanceUsingPluginWithSlashes() {
   public function testCreateInstanceDefaultFallback() {
     $this->classResolver->getInstanceFromDefinition(Argument::cetera())->shouldNotBeCalled();
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class)->willImplement(PluginFormInterface::class);
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'fallback' => get_class($plugin->reveal()),
-      ],
-    ]);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class)->willImplement(PluginFormInterface::class);
+    $plugin->hasFormClass('missing')->willReturn(FALSE);
+    $plugin->hasFormClass('fallback')->willReturn(TRUE);
+    $plugin->getFormClass('fallback')->willReturn(get_class($plugin->reveal()));
 
     $form_object = $this->manager->createInstance($plugin->reveal(), 'missing', 'fallback');
     $this->assertSame($plugin->reveal(), $form_object);
@@ -140,12 +111,9 @@ public function testCreateInstancePluginAware() {
 
     $this->classResolver->getInstanceFromDefinition(get_class($expected))->willReturn($expected);
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class);
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'operation_aware' => get_class($expected),
-      ],
-    ]);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class);
+    $plugin->hasFormClass('operation_aware')->willReturn(TRUE);
+    $plugin->getFormClass('operation_aware')->willReturn(get_class($expected));
 
     $plugin_form->setPlugin($plugin->reveal())->shouldBeCalled();
 
@@ -159,9 +127,9 @@ public function testCreateInstancePluginAware() {
   public function testCreateInstanceDefinitionException() {
     $this->setExpectedException(InvalidPluginDefinitionException::class, 'The "the_plugin_id" plugin did not specify a "anything" form class');
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class);
     $plugin->getPluginId()->willReturn('the_plugin_id');
-    $plugin->getPluginDefinition()->willReturn([]);
+    $plugin->hasFormClass('anything')->willReturn(FALSE);
 
     $form_object = $this->manager->createInstance($plugin->reveal(), 'anything');
     $this->assertSame(NULL, $form_object);
@@ -176,13 +144,10 @@ public function testCreateInstanceInvalidException() {
     $expected = new \stdClass();
     $this->classResolver->getInstanceFromDefinition(get_class($expected))->willReturn($expected);
 
-    $plugin = $this->prophesize(PluginInspectionInterface::class);
+    $plugin = $this->prophesize(PluginWithFormsInterface::class);
     $plugin->getPluginId()->willReturn('the_plugin_id');
-    $plugin->getPluginDefinition()->willReturn([
-      'forms' => [
-        'invalid' => get_class($expected),
-      ],
-    ]);
+    $plugin->hasFormClass('invalid')->willReturn(TRUE);
+    $plugin->getFormClass('invalid')->willReturn(get_class($expected));
 
     $form_object = $this->manager->createInstance($plugin->reveal(), 'invalid');
     $this->assertSame(NULL, $form_object);