diff --git a/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
index 2428109..62f3dd3 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
+++ b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
@@ -35,7 +35,7 @@ public function __construct(DiscoveryInterface $decorated) {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
 
     list($base_plugin_id, $derivative_id) = $this->decodePluginId($plugin_id);
 
@@ -45,7 +45,7 @@ public function getDefinition($plugin_id, $exception = TRUE) {
       if ($derivative_fetcher) {
         $plugin_definition = $derivative_fetcher->getDerivativeDefinition($derivative_id, $plugin_definition);
         if (!isset($plugin_definition)) {
-          if ($exception) {
+          if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
             // @todo will this handle nested derivatives gracefuly?
             throw new DerivativeNotFoundException(sprintf('Derivative plugin "%s", derived from base plugin "%s", could not be found.', $base_plugin_id, $derivative_id));
           }
diff --git a/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryInterface.php b/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryInterface.php
index f1c55d6..5659b60 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryInterface.php
+++ b/core/lib/Drupal/Component/Plugin/Discovery/DiscoveryInterface.php
@@ -15,6 +15,9 @@
  */
 interface DiscoveryInterface {
 
+  const EXCEPTION_ON_INVALID_ID = 1;
+  const NULL_ON_INVALID_ID = 2;
+
   /**
    * Gets a specific plugin definition.
    *
@@ -29,7 +32,7 @@
    *
    * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
    */
-  public function getDefinition($plugin_id, $exception = TRUE);
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID);
 
   /**
    * Gets the definition of all plugins for this type.
diff --git a/core/lib/Drupal/Component/Plugin/Discovery/StaticDiscovery.php b/core/lib/Drupal/Component/Plugin/Discovery/StaticDiscovery.php
index 56bb240..080854f 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/StaticDiscovery.php
+++ b/core/lib/Drupal/Component/Plugin/Discovery/StaticDiscovery.php
@@ -25,11 +25,11 @@ class StaticDiscovery implements DiscoveryInterface {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
    */
-  public function getDefinition($base_plugin_id, $exception = TRUE) {
+  public function getDefinition($base_plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     if (isset($this->definitions[$base_plugin_id])) {
       return $this->definitions[$base_plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
       throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $base_plugin_id));;
     }
   }
diff --git a/core/lib/Drupal/Component/Plugin/PluginManagerBase.php b/core/lib/Drupal/Component/Plugin/PluginManagerBase.php
index ee9115e..85af54c 100644
--- a/core/lib/Drupal/Component/Plugin/PluginManagerBase.php
+++ b/core/lib/Drupal/Component/Plugin/PluginManagerBase.php
@@ -49,16 +49,22 @@
   /**
    * Implements Drupal\Component\Plugin\PluginManagerInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     try {
-      $definition = $this->discovery->getDefinition($plugin_id, $exception);
+      $definition = $this->discovery->getDefinition($plugin_id, $invalid_behavior);
     }
     catch (PluginNotFoundException $e) {
-      throw new PluginNotFoundException(sprintf('Plugin manager "%s" was unable to find plugin with id "%s".', get_class($this), $plugin_id), E_RECOVERABLE_ERROR, $e);
+      $refl = new \ReflectionClass($e);
+      // Ensure we reproduce the exact same exception type, even if a child class.
+      // @todo this is horrible. can we make this better?
+      throw $refl->newInstance(sprintf('Plugin manager "%s" was unable to find plugin with id "%s".', get_class($this), $plugin_id), E_RECOVERABLE_ERROR, $e);
+      // throw new PluginNotFoundException(sprintf('Plugin manager "%s" was unable to find plugin with id "%s".', get_class($this), $plugin_id), E_RECOVERABLE_ERROR, $e);
     }
 
-    $this->processDefinition($definition, $plugin_id);
-    return $definition;
+    if (!is_null($definition)) {
+      $this->processDefinition($definition, $plugin_id);
+      return $definition;
+    }
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Plugin/Discovery/AlterDecorator.php b/core/lib/Drupal/Core/Plugin/Discovery/AlterDecorator.php
index f7f3aa1..fab047f 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/AlterDecorator.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/AlterDecorator.php
@@ -46,12 +46,12 @@ public function __construct(DiscoveryInterface $decorated, $hook) {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$plugin_id])) {
       return $definitions[$plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
       throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $plugin_id));;
     }
   }
diff --git a/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php b/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
index 2891e68..74380f5 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
@@ -32,12 +32,12 @@ function __construct($owner, $type) {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$plugin_id])) {
       return $definitions[$plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
       throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $plugin_id));;
     }
   }
diff --git a/core/lib/Drupal/Core/Plugin/Discovery/CacheDecorator.php b/core/lib/Drupal/Core/Plugin/Discovery/CacheDecorator.php
index 641b2d3..b482567 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/CacheDecorator.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/CacheDecorator.php
@@ -65,12 +65,12 @@ public function __construct(DiscoveryInterface $decorated, $cache_key, $cache_bi
   /**
    * Implements Drupal\Component\Plugin\Discovery\DicoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$plugin_id])) {
       return $definitions[$plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
       throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $plugin_id));;
     }
   }
diff --git a/core/lib/Drupal/Core/Plugin/Discovery/HookDiscovery.php b/core/lib/Drupal/Core/Plugin/Discovery/HookDiscovery.php
index 10a2462..b7c6d3c 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/HookDiscovery.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/HookDiscovery.php
@@ -36,12 +36,12 @@ function __construct($hook) {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DicoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$plugin_id])) {
       return $definitions[$plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
       throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $plugin_id));;
     }
   }
diff --git a/core/lib/Drupal/Core/Plugin/Discovery/InfoHookDecorator.php b/core/lib/Drupal/Core/Plugin/Discovery/InfoHookDecorator.php
index deddb31..04b4418 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/InfoHookDecorator.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/InfoHookDecorator.php
@@ -45,12 +45,12 @@ public function __construct(DiscoveryInterface $decorated, $hook) {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$plugin_id])) {
       return $definitions[$plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
         throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $plugin_id));;
     }
   }
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterPluginManager.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterPluginManager.php
index 6c3840e..ee81484 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterPluginManager.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Formatter/FormatterPluginManager.php
@@ -8,6 +8,7 @@
 namespace Drupal\field\Plugin\Type\Formatter;
 
 use Drupal\Component\Plugin\PluginManagerBase;
+use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
 use Drupal\Core\Plugin\Discovery\CacheDecorator;
 use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
 use Drupal\field\Plugin\Type\Formatter\FormatterLegacyDiscoveryDecorator;
@@ -45,7 +46,7 @@ public function getInstance(array $options) {
     $instance = $options['instance'];
     $type = $options['type'];
 
-    $definition = $this->getDefinition($type, FALSE);
+    $definition = $this->getDefinition($type, DiscoveryInterface::NULL_ON_INVALID_ID);
     $field = field_info_field($instance['field_name']);
 
     // Switch back to default formatter if either:
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php b/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php
index b74c8db..dbedd66 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/LegacyDiscoveryDecorator.php
@@ -47,12 +47,12 @@ public function __construct(DiscoveryInterface $decorated) {
   /**
    * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinition().
    */
-  public function getDefinition($plugin_id, $exception = TRUE) {
+  public function getDefinition($plugin_id, $invalid_behavior = self::EXCEPTION_ON_INVALID_ID) {
     $definitions = $this->getDefinitions();
     if (isset($definitions[$plugin_id])) {
       return $definitions[$plugin_id];
     }
-    else if ($exception) {
+    else if ($invalid_behavior === self::EXCEPTION_ON_INVALID_ID) {
       throw new PluginNotFoundException(sprintf('The plugin (%s) could not be found.', $plugin_id));;
     }
   }
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetPluginManager.php b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetPluginManager.php
index 99f379e..26c10b6 100644
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetPluginManager.php
+++ b/core/modules/field/lib/Drupal/field/Plugin/Type/Widget/WidgetPluginManager.php
@@ -8,6 +8,7 @@
 namespace Drupal\field\Plugin\Type\Widget;
 
 use Drupal\Component\Plugin\PluginManagerBase;
+use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
 use Drupal\Core\Plugin\Discovery\CacheDecorator;
 use Drupal\Core\Plugin\Discovery\AlterDecorator;
 use Drupal\Core\Plugin\Discovery\AnnotatedClassDiscovery;
@@ -46,7 +47,7 @@ public function getInstance(array $options) {
     $instance = $options['instance'];
     $type = $options['type'];
 
-    $definition = $this->getDefinition($type, TRUE);
+    $definition = $this->getDefinition($type, DiscoveryInterface::NULL_ON_INVALID_ID);
     $field = field_info_field($instance['field_name']);
 
     // Switch back to default widget if either:
diff --git a/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php
index 327e46e..eb5098c 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Plugin/CacheDecoratorTest.php
@@ -122,7 +122,7 @@ public function testClearCachedDefinitions() {
     $this->discovery->setDefinition('banana', $this->expectedDefinitions['banana']);
 
     // Check that the new definition is not found.
-    $definition = $this->discovery->getDefinition('banana');
+    $definition = $this->discovery->getDefinition('banana', FALSE);
     $this->assertNull($definition, 'Newly added definition is not found.');
 
     // Clear cached definitions, and check that the new definition is found.