DerivativeDiscoveryDecorator doesn't check/enforce the proposed derivative fetchers implement interface DerivativeInterface

+++ b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
@@ -148,6 +150,27 @@ protected function getDerivativeFetcher($base_plugin_id, array $base_definition)
+   * @throws Drupal\Component\Plugin\Exception\PluginException

Let's add leading "\" here as well.

Might be a good place for an explicit exception that extends the base plugin exception.

+++ b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
@@ -152,10 +152,13 @@ protected function getDerivativeFetcher($base_plugin_id, array $base_definition)
+   * @throws \Drupal\Component\Plugin\Exception\PluginException
    *   Thrown if the class in the definition does not implement the expected

Woops, wrong exception name.

+++ b/core/lib/Drupal/Component/Plugin/Exception/InvalidDerivativeClassException.php
@@ -0,0 +1,13 @@
+/**
+ * Exception class to be thrown if a plugin tries to use derivative class that
+ * is invalid, such as not implementing the expected interface.
+ */
+class InvalidDerivativeClassException extends PluginException { }

*tries to use an invalid derivative class

+++ b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
@@ -2,11 +2,13 @@
- * Definition of Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator.
+ * Definition of \Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator.

+++ b/core/lib/Drupal/Component/Plugin/Exception/InvalidDerivativeClassException.php
@@ -0,0 +1,12 @@
+ * Definition of \Drupal\Component\Plugin\Exception\InvalidDerivativeClassException.

Fixing this is kind of out of scope, but if we do, we should do it properly: "Contains \..."

Sure sure, just wanted to do it properly here.

Don't have an answer but should be public method be clear that it can throw an exception since we're not catching it internally?

Yes, that's what I meant. Lets go ahead and do it then.

So we need kind of something like this?

.

Exactly. Making assumptions about the bot return since this is a doc change and bumping back to RTBC. Everything thing else looks awesome.

Good enough for me. Back to RTBC.

Patch no longer applies.

Re-roll.

Back to RTBC

#28: drupal_2078879_28.patch queued for re-testing.

Committed/pushed to 8.x, thanks!

+++ b/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php
@@ -133,14 +143,18 @@ protected function encodePluginId($base_plugin_id, $derivative_id) {
+   * @return \Drupal\Component\Plugin\Derivative\DerivativeInterface|null
++   *   A DerivativeInterface or NULL if none exists for the plugin.
++   *
++   * @throws \Drupal\Component\Plugin\Exception\InvalidDerivativeClassException
++   *   Thrown if the 'derivative' class specified in the plugin definition does
++   *   not implement \Drupal\Component\Plugin\Derivative\DerivativeInterface.

Can we get a quick follow-up for the wrong patch-style documentation here? Thanks!